Hey all;

I'm trying to repair an old tube portable record player. When it is on, it
hums really loud, regardless of the volume. I assumed that this must be a
problem with filter caps, but they test OK for ESR and shorts. 1 of the
problems is that there are 3 or 4 in a can, so I don't know what the values
are supposed to be.

Is there anything else that may cause this symptom? I suppose I could
parallel some caps across the existing ones, but I don't even know what the
values are supposed to be.

Thanks

You could be getting hum through the tonearm wires to the pickup,
but I'd bet on filter capacitors.

tempus fugit wrote:
Hey all;

I'm trying to repair an old tube portable record player. When it is on, it
hums really loud, regardless of the volume. I assumed that this must be a
problem with filter caps, but they test OK for ESR and shorts. 1 of the
problems is that there are 3 or 4 in a can, so I don't know what the values
are supposed to be.

Is there anything else that may cause this symptom? I suppose I could
parallel some caps across the existing ones, but I don't even know what the
values are supposed to be.

Thanks

tempus fugit wrote:

Hey all;

I'm trying to repair an old tube portable record player. When it is on, it
hums really loud, regardless of the volume. I assumed that this must be a
problem with filter caps, but they test OK for ESR and shorts. 1 of the
problems is that there are 3 or 4 in a can, so I don't know what the values
are supposed to be.

Is there anything else that may cause this symptom? I suppose I could
parallel some caps across the existing ones, but I don't even know what the
values are supposed to be.

Thanks



One or more diodes in the power supply (assuming it uses them) is
shorted. If it has a rectifier tube instead of semiconductor diodes,
then either the tube is shorted or, if it has its own filament supply
(e.g. 5U4), then that supply could be shorted inside or outside of the
power transformer (assuming it has a transformer), although there's a
pretty good chance the tube would be glowing bright red if that were
the case. If it's all tube and has no power transformer, then you've
got a potentially lethal hot chassis and you'd better be d*mned careful.
Check for shorted line bypass capacitors if it's this last case.

Or it could be one or more capacitors, as earlier suggested, or a break
in some shielding.

As you can surmise, additional information about the circuit involved
could narrow the possibilities (and possibly suggest others).

--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

Thanks for your reply.

Sorry, here's some more info:

There is a power transformer.
Only 1 diode that I could see.
Measured voltages at cap in question was ~150v.
Only 2 tubes - 12AX7 and can't remember the power tube offhand.

There was also some small device which I assume was a transformer that hadd
100mA marked on it. It looked like a trasformer with cooling fins.


"CJT" wrote in message
...
tempus fugit wrote:

Hey all;

I'm trying to repair an old tube portable record player. When it is on,
it
hums really loud, regardless of the volume. I assumed that this must be
a
problem with filter caps, but they test OK for ESR and shorts. 1 of the
problems is that there are 3 or 4 in a can, so I don't know what the
values
are supposed to be.

Is there anything else that may cause this symptom? I suppose I could
parallel some caps across the existing ones, but I don't even know what
the
values are supposed to be.

Thanks



One or more diodes in the power supply (assuming it uses them) is
shorted. If it has a rectifier tube instead of semiconductor diodes,
then either the tube is shorted or, if it has its own filament supply
(e.g. 5U4), then that supply could be shorted inside or outside of the
power transformer (assuming it has a transformer), although there's a
pretty good chance the tube would be glowing bright red if that were
the case. If it's all tube and has no power transformer, then you've
got a potentially lethal hot chassis and you'd better be d*mned careful.
Check for shorted line bypass capacitors if it's this last case.

Or it could be one or more capacitors, as earlier suggested, or a break
in some shielding.

As you can surmise, additional information about the circuit involved
could narrow the possibilities (and possibly suggest others).

--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

"tempus fugit" bravely wrote to "All" (27 Oct 05 11:17:42)
--- on the heady topic of "unit hums loudly regardless of volume"

tf From: "tempus fugit"
tf Xref: core-easynews sci.electronics.repair:346437

tf Hey all;

tf I'm trying to repair an old tube portable record player. When it is
tf on, it hums really loud, regardless of the volume.

Have you tried turning the ac plug around?

Which way the plug is inserted matters with these. Let the record
player warm up, then insert the plug one way or the other, and then
paint a mark for which was the quietest way. One way: lots of hum, the
other: quiet hiss.

Those old tube units used to get B+ directly from the powerline (or
sometimes a voltage doubler) and used a large value resistor bypassed
by a 0.01uF to RF ground the tone arm shielding to neutral. The power
for the filaments often came from a secondary winding in the motor
coil. Don't use this type of record player near the bathtub. Lethal!

Another possibility is a broken wire at the cartridge.

A*s*i*m*o*v

.... Just a little force field zap.

tempus fugit wrote:

Thanks for your reply.

Sorry, here's some more info:

There is a power transformer.
Only 1 diode that I could see.
Measured voltages at cap in question was ~150v.

If the cap had DC on it, the diode is probably ok. The capacitor(s)
could be dried out (although I think you said you checked them, so
that's not too likely). From there, you move toward shielding type
problems as already described elsewhere in the thread.

Only 2 tubes - 12AX7 and can't remember the power tube offhand.

If one of the tubes had an internal heater-to-cathode short (or for
that matter, a short at the tube socket), that could cause a lot of hum.
Such shorts are not uncommon.

At any rate, now you have plenty of ideas to consider.

There was also some small device which I assume was a transformer that hadd
100mA marked on it. It looked like a trasformer with cooling fins.


"CJT" wrote in message
...

tempus fugit wrote:


Hey all;

I'm trying to repair an old tube portable record player. When it is on,

it

hums really loud, regardless of the volume. I assumed that this must be

a

problem with filter caps, but they test OK for ESR and shorts. 1 of the
problems is that there are 3 or 4 in a can, so I don't know what the

values

are supposed to be.

Is there anything else that may cause this symptom? I suppose I could
parallel some caps across the existing ones, but I don't even know what

the

values are supposed to be.

Thanks




One or more diodes in the power supply (assuming it uses them) is
shorted. If it has a rectifier tube instead of semiconductor diodes,
then either the tube is shorted or, if it has its own filament supply
(e.g. 5U4), then that supply could be shorted inside or outside of the
power transformer (assuming it has a transformer), although there's a
pretty good chance the tube would be glowing bright red if that were
the case. If it's all tube and has no power transformer, then you've
got a potentially lethal hot chassis and you'd better be d*mned careful.
Check for shorted line bypass capacitors if it's this last case.

Or it could be one or more capacitors, as earlier suggested, or a break
in some shielding.

As you can surmise, additional information about the circuit involved
could narrow the possibilities (and possibly suggest others).

--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .





--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

"CJT" wrote in message
...
tempus fugit wrote:

Thanks for your reply.

Sorry, here's some more info:

There is a power transformer.
Only 1 diode that I could see.
Measured voltages at cap in question was ~150v.

If the cap had DC on it, the diode is probably ok. The capacitor(s)
could be dried out (although I think you said you checked them, so
that's not too likely). From there, you move toward shielding type
problems as already described elsewhere in the thread.

Only 2 tubes - 12AX7 and can't remember the power tube offhand.

If one of the tubes had an internal heater-to-cathode short (or for
that matter, a short at the tube socket), that could cause a lot of hum.
Such shorts are not uncommon.

At any rate, now you have plenty of ideas to consider.

There was also some small device which I assume was a transformer that
hadd
100mA marked on it. It looked like a trasformer with cooling fins.

possibly a selenium rectifier. back in the old days they hadn't figured out
to make high voltage silicon diodes yet.

the usual warnings about selenium: emits poison gas when it burns

replace with modern diodes is recommended.

Thanks for the suggestions guys. I'll try some of these things out.


"Asimov" wrote in message
...
"tempus fugit" bravely wrote to "All" (27 Oct 05 11:17:42)
--- on the heady topic of "unit hums loudly regardless of volume"

tf From: "tempus fugit"
tf Xref: core-easynews sci.electronics.repair:346437

tf Hey all;

tf I'm trying to repair an old tube portable record player. When it is
tf on, it hums really loud, regardless of the volume.

Have you tried turning the ac plug around?

Which way the plug is inserted matters with these. Let the record
player warm up, then insert the plug one way or the other, and then
paint a mark for which was the quietest way. One way: lots of hum, the
other: quiet hiss.

Those old tube units used to get B+ directly from the powerline (or
sometimes a voltage doubler) and used a large value resistor bypassed
by a 0.01uF to RF ground the tone arm shielding to neutral. The power
for the filaments often came from a secondary winding in the motor
coil. Don't use this type of record player near the bathtub. Lethal!

Another possibility is a broken wire at the cartridge.

A*s*i*m*o*v

.... Just a little force field zap.

Change the A.C. filter capacitor that should cure usually in the 10's of
microfarids at 150V
"tempus fugit" wrote in message
...
Thanks for the suggestions guys. I'll try some of these things out.


"Asimov" wrote in message
...
"tempus fugit" bravely wrote to "All" (27 Oct 05 11:17:42)
--- on the heady topic of "unit hums loudly regardless of volume"

tf From: "tempus fugit"
tf Xref: core-easynews sci.electronics.repair:346437

tf Hey all;

tf I'm trying to repair an old tube portable record player. When it is
tf on, it hums really loud, regardless of the volume.

Have you tried turning the ac plug around?

Which way the plug is inserted matters with these. Let the record
player warm up, then insert the plug one way or the other, and then
paint a mark for which was the quietest way. One way: lots of hum, the
other: quiet hiss.

Those old tube units used to get B+ directly from the powerline (or
sometimes a voltage doubler) and used a large value resistor bypassed
by a 0.01uF to RF ground the tone arm shielding to neutral. The power
for the filaments often came from a secondary winding in the motor
coil. Don't use this type of record player near the bathtub. Lethal!

Another possibility is a broken wire at the cartridge.

A*s*i*m*o*v

... Just a little force field zap.

That sounds more like a selenium rectifier -- if it were bad
you'd smell it!

tempus fugit wrote:

There was also some small device which I assume was a transformer that hadd
100mA marked on it. It looked like a trasformer with cooling fins.

mark wrote:
Change the A.C. filter capacitor that should cure usually in the 10's of
microfarids at 150V

If the voltage on it measures 150V, then a 250V cap might be a better
choice for a replacement.

"tempus fugit" wrote in message
...

Thanks for the suggestions guys. I'll try some of these things out.


"Asimov" wrote in message
. ..
"tempus fugit" bravely wrote to "All" (27 Oct 05 11:17:42)
--- on the heady topic of "unit hums loudly regardless of volume"

tf From: "tempus fugit"
tf Xref: core-easynews sci.electronics.repair:346437

tf Hey all;

tf I'm trying to repair an old tube portable record player. When it is
tf on, it hums really loud, regardless of the volume.

Have you tried turning the ac plug around?

Which way the plug is inserted matters with these. Let the record
player warm up, then insert the plug one way or the other, and then
paint a mark for which was the quietest way. One way: lots of hum, the
other: quiet hiss.

Those old tube units used to get B+ directly from the powerline (or
sometimes a voltage doubler) and used a large value resistor bypassed
by a 0.01uF to RF ground the tone arm shielding to neutral. The power
for the filaments often came from a secondary winding in the motor
coil. Don't use this type of record player near the bathtub. Lethal!

Another possibility is a broken wire at the cartridge.

A*s*i*m*o*v

... Just a little force field zap.







--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

Tried the turining around the plug trick, but it made no difference. I also
disconnected the phono plug that connects the tone arm to the amp unit,
which also made no difference.

Here is something curious though. I accidentally touched my scope while my
hand was on the record player chassis and got a fairly good shock. The scope
has a 3 prong AC plug (the record player doesn't). I should've measured the
voltage difference between the sope chassis and the record player chassis,
but I didn't think to. I'll have to do that. Perhaps he chassis is live. I
didn't think this would be the case though, since there is a cap with the
negative connected to the case, as well as a few other green wires.

Thanks


"Asimov" wrote in message
...
"tempus fugit" bravely wrote to "All" (27 Oct 05 11:17:42)
--- on the heady topic of "unit hums loudly regardless of volume"

tf From: "tempus fugit"
tf Xref: core-easynews sci.electronics.repair:346437

tf Hey all;

tf I'm trying to repair an old tube portable record player. When it is
tf on, it hums really loud, regardless of the volume.

Have you tried turning the ac plug around?

Which way the plug is inserted matters with these. Let the record
player warm up, then insert the plug one way or the other, and then
paint a mark for which was the quietest way. One way: lots of hum, the
other: quiet hiss.

Those old tube units used to get B+ directly from the powerline (or
sometimes a voltage doubler) and used a large value resistor bypassed
by a 0.01uF to RF ground the tone arm shielding to neutral. The power
for the filaments often came from a secondary winding in the motor
coil. Don't use this type of record player near the bathtub. Lethal!

Another possibility is a broken wire at the cartridge.

A*s*i*m*o*v

.... Just a little force field zap.

tempus fugit wrote:

Tried the turining around the plug trick, but it made no difference. I also
disconnected the phono plug that connects the tone arm to the amp unit,
which also made no difference.

Here is something curious though. I accidentally touched my scope while my
hand was on the record player chassis and got a fairly good shock. The scope
has a 3 prong AC plug (the record player doesn't). I should've measured the
voltage difference between the sope chassis and the record player chassis,
but I didn't think to. I'll have to do that. Perhaps he chassis is live. I
didn't think this would be the case though, since there is a cap with the
negative connected to the case, as well as a few other green wires.


That capacitor might be leaking or (worse) shorted. It can be a lethal
failure (I read just this week about a minister in Waco who was
electrocuted during a baptism when he grabbed a microphone that was
"hot."). Be careful.

Thanks


"Asimov" wrote in message
...
"tempus fugit" bravely wrote to "All" (27 Oct 05 11:17:42)
--- on the heady topic of "unit hums loudly regardless of volume"

tf From: "tempus fugit"
tf Xref: core-easynews sci.electronics.repair:346437

tf Hey all;

tf I'm trying to repair an old tube portable record player. When it is
tf on, it hums really loud, regardless of the volume.

Have you tried turning the ac plug around?

Which way the plug is inserted matters with these. Let the record
player warm up, then insert the plug one way or the other, and then
paint a mark for which was the quietest way. One way: lots of hum, the
other: quiet hiss.

Those old tube units used to get B+ directly from the powerline (or
sometimes a voltage doubler) and used a large value resistor bypassed
by a 0.01uF to RF ground the tone arm shielding to neutral. The power
for the filaments often came from a secondary winding in the motor
coil. Don't use this type of record player near the bathtub. Lethal!

Another possibility is a broken wire at the cartridge.

A*s*i*m*o*v

... Just a little force field zap.




--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

CJT wrote:

tempus fugit wrote:

Tried the turining around the plug trick, but it made no difference. I
also
disconnected the phono plug that connects the tone arm to the amp unit,
which also made no difference.

Here is something curious though. I accidentally touched my scope
while my
hand was on the record player chassis and got a fairly good shock. The
scope
has a 3 prong AC plug (the record player doesn't). I should've
measured the
voltage difference between the sope chassis and the record player
chassis,
but I didn't think to. I'll have to do that. Perhaps he chassis is
live. I
didn't think this would be the case though, since there is a cap with the
negative connected to the case, as well as a few other green wires.


That capacitor might be leaking or (worse) shorted. It can be a lethal
failure (I read just this week about a minister in Waco who was
electrocuted during a baptism when he grabbed a microphone that was
"hot."). Be careful.


Here's a cite to that story:
http://www.cbsnews.com/stories/2005/...in995829.shtml

Thanks


"Asimov" wrote in
message
...
"tempus fugit" bravely wrote to "All" (27 Oct 05 11:17:42)
--- on the heady topic of "unit hums loudly regardless of volume"

tf From: "tempus fugit"
tf Xref: core-easynews sci.electronics.repair:346437

tf Hey all;

tf I'm trying to repair an old tube portable record player. When it is
tf on, it hums really loud, regardless of the volume.

Have you tried turning the ac plug around?

Which way the plug is inserted matters with these. Let the record
player warm up, then insert the plug one way or the other, and then
paint a mark for which was the quietest way. One way: lots of hum, the
other: quiet hiss.

Those old tube units used to get B+ directly from the powerline (or
sometimes a voltage doubler) and used a large value resistor bypassed
by a 0.01uF to RF ground the tone arm shielding to neutral. The power
for the filaments often came from a secondary winding in the motor
coil. Don't use this type of record player near the bathtub. Lethal!

Another possibility is a broken wire at the cartridge.

A*s*i*m*o*v

... Just a little force field zap.






--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

I tested the cap and it showed about a half meg of resistance. maybe
something is shorted somehwere else. Oh, and I checked the voltage between
the record player chassis and the scope chassis - 120VAC (I thought that's
what it felt like). Odd though, I would think with 120v on the chassis that
it would pop a fuse at the breaker box.

Thanks


"CJT" wrote in message
...
CJT wrote:

tempus fugit wrote:

Tried the turining around the plug trick, but it made no difference. I
also
disconnected the phono plug that connects the tone arm to the amp unit,
which also made no difference.

Here is something curious though. I accidentally touched my scope
while my
hand was on the record player chassis and got a fairly good shock. The
scope
has a 3 prong AC plug (the record player doesn't). I should've
measured the
voltage difference between the sope chassis and the record player
chassis,
but I didn't think to. I'll have to do that. Perhaps he chassis is
live. I
didn't think this would be the case though, since there is a cap with
the
negative connected to the case, as well as a few other green wires.


That capacitor might be leaking or (worse) shorted. It can be a lethal
failure (I read just this week about a minister in Waco who was
electrocuted during a baptism when he grabbed a microphone that was
"hot."). Be careful.


Here's a cite to that story:
http://www.cbsnews.com/stories/2005/...in995829.shtml

Thanks


"Asimov" wrote in
message
...
"tempus fugit" bravely wrote to "All" (27 Oct 05 11:17:42)
--- on the heady topic of "unit hums loudly regardless of volume"

tf From: "tempus fugit"
tf Xref: core-easynews sci.electronics.repair:346437

tf Hey all;

tf I'm trying to repair an old tube portable record player. When it
is
tf on, it hums really loud, regardless of the volume.

Have you tried turning the ac plug around?

Which way the plug is inserted matters with these. Let the record
player warm up, then insert the plug one way or the other, and then
paint a mark for which was the quietest way. One way: lots of hum, the
other: quiet hiss.

Those old tube units used to get B+ directly from the powerline (or
sometimes a voltage doubler) and used a large value resistor bypassed
by a 0.01uF to RF ground the tone arm shielding to neutral. The power
for the filaments often came from a secondary winding in the motor
coil. Don't use this type of record player near the bathtub. Lethal!

Another possibility is a broken wire at the cartridge.

A*s*i*m*o*v

... Just a little force field zap.






--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

tempus fugit wrote:

I tested the cap and it showed about a half meg of resistance.

We're talking about a capacitor between the chassis and one side
of the line, right?

It should be infinite (assuming you tested it out of the circuit).

When in doubt, replace it (or just snip it out and don't replace it).
Google "death cap" if you'd like some further opinions, typically from
the world of guitar amps.

maybe
something is shorted somehwere else. Oh, and I checked the voltage between
the record player chassis and the scope chassis - 120VAC

Reversing the plug in the wall socket should change that (but don't
count on it).

(I thought that's
what it felt like). Odd though, I would think with 120v on the chassis that
it would pop a fuse at the breaker box.

Not until your hair catches fire.

You really need to be careful with this device. I can't stress that
enough. Death is not to be trifled with.

Thanks


"CJT" wrote in message
...

CJT wrote:


tempus fugit wrote:


Tried the turining around the plug trick, but it made no difference. I
also
disconnected the phono plug that connects the tone arm to the amp unit,
which also made no difference.

Here is something curious though. I accidentally touched my scope
while my
hand was on the record player chassis and got a fairly good shock. The
scope
has a 3 prong AC plug (the record player doesn't). I should've
measured the
voltage difference between the sope chassis and the record player
chassis,
but I didn't think to. I'll have to do that. Perhaps he chassis is
live. I
didn't think this would be the case though, since there is a cap with

the

negative connected to the case, as well as a few other green wires.


That capacitor might be leaking or (worse) shorted. It can be a lethal
failure (I read just this week about a minister in Waco who was
electrocuted during a baptism when he grabbed a microphone that was
"hot."). Be careful.


Here's a cite to that story:
http://www.cbsnews.com/stories/2005/...in995829.shtml


Thanks


"Asimov" wrote in
message
g...
"tempus fugit" bravely wrote to "All" (27 Oct 05 11:17:42)
--- on the heady topic of "unit hums loudly regardless of volume"

tf From: "tempus fugit"
tf Xref: core-easynews sci.electronics.repair:346437

tf Hey all;

tf I'm trying to repair an old tube portable record player. When it

is

tf on, it hums really loud, regardless of the volume.

Have you tried turning the ac plug around?

Which way the plug is inserted matters with these. Let the record
player warm up, then insert the plug one way or the other, and then
paint a mark for which was the quietest way. One way: lots of hum, the
other: quiet hiss.

Those old tube units used to get B+ directly from the powerline (or
sometimes a voltage doubler) and used a large value resistor bypassed
by a 0.01uF to RF ground the tone arm shielding to neutral. The power
for the filaments often came from a secondary winding in the motor
coil. Don't use this type of record player near the bathtub. Lethal!

Another possibility is a broken wire at the cartridge.

A*s*i*m*o*v

... Just a little force field zap.





--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .





--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

We're talking about a capacitor between the chassis and one side
of the line, right?

I havent reopened the chassis, but it seems to be connected between the
ground of the speaker and the chassis.

something is shorted somehwere else. Oh, and I checked the voltage
between
the record player chassis and the scope chassis - 120VAC

Reversing the plug in the wall socket should change that (but don't
count on it).

Reversing the plug did correct that. Is this a design shortcoming (if so,
there's gotta be a safer way to set that up) or should I be looking for a
fault somewhere?



You really need to be careful with this device. I can't stress that
enough. Death is not to be trifled with.

I am being very careful, not to worry, but I appreciate your concern and
helpful advice (including those on personal safety).

Thanks again


Thanks


"CJT" wrote in message
...

CJT wrote:


tempus fugit wrote:


Tried the turining around the plug trick, but it made no difference. I
also
disconnected the phono plug that connects the tone arm to the amp
unit,
which also made no difference.

Here is something curious though. I accidentally touched my scope
while my
hand was on the record player chassis and got a fairly good shock. The
scope
has a 3 prong AC plug (the record player doesn't). I should've
measured the
voltage difference between the sope chassis and the record player
chassis,
but I didn't think to. I'll have to do that. Perhaps he chassis is
live. I
didn't think this would be the case though, since there is a cap with

the

negative connected to the case, as well as a few other green wires.


That capacitor might be leaking or (worse) shorted. It can be a lethal
failure (I read just this week about a minister in Waco who was
electrocuted during a baptism when he grabbed a microphone that was
"hot."). Be careful.


Here's a cite to that story:
http://www.cbsnews.com/stories/2005/...in995829.shtml


Thanks


"Asimov" wrote in
message
g...
"tempus fugit" bravely wrote to "All" (27 Oct 05 11:17:42)
--- on the heady topic of "unit hums loudly regardless of volume"

tf From: "tempus fugit"
tf Xref: core-easynews sci.electronics.repair:346437

tf Hey all;

tf I'm trying to repair an old tube portable record player. When it

is

tf on, it hums really loud, regardless of the volume.

Have you tried turning the ac plug around?

Which way the plug is inserted matters with these. Let the record
player warm up, then insert the plug one way or the other, and then
paint a mark for which was the quietest way. One way: lots of hum, the
other: quiet hiss.

Those old tube units used to get B+ directly from the powerline (or
sometimes a voltage doubler) and used a large value resistor bypassed
by a 0.01uF to RF ground the tone arm shielding to neutral. The power
for the filaments often came from a secondary winding in the motor
coil. Don't use this type of record player near the bathtub. Lethal!

Another possibility is a broken wire at the cartridge.

A*s*i*m*o*v

... Just a little force field zap.





--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .





--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

tempus fugit wrote:

We're talking about a capacitor between the chassis and one side
of the line, right?


I havent reopened the chassis, but it seems to be connected between the
ground of the speaker and the chassis.

OK, that's something totally different.



something is shorted somehwere else. Oh, and I checked the voltage

between

the record player chassis and the scope chassis - 120VAC

Reversing the plug in the wall socket should change that (but don't
count on it).


Reversing the plug did correct that. Is this a design shortcoming (if so,
there's gotta be a safer way to set that up) or should I be looking for a
fault somewhere?


That's normal for a "hot chassis" device. But such a device won't have
a power transformer, and I thought you said this one did. Could you be
confusing an output transformer with a power transformer?

If you are (and I suspect you are) then you are such a newbie that you
had better stop now and enlist the help of somebody who knows what
they're doing before you kill yourself. No kidding. I don't want to
have anything more to do with this pursuit.

tempus may fugit, but not for the dead



You really need to be careful with this device. I can't stress that
enough. Death is not to be trifled with.


I am being very careful, not to worry, but I appreciate your concern and
helpful advice (including those on personal safety).

Thanks again


Thanks


"CJT" wrote in message
...


CJT wrote:



tempus fugit wrote:



Tried the turining around the plug trick, but it made no difference. I
also
disconnected the phono plug that connects the tone arm to the amp

unit,

which also made no difference.

Here is something curious though. I accidentally touched my scope
while my
hand was on the record player chassis and got a fairly good shock. The
scope
has a 3 prong AC plug (the record player doesn't). I should've
measured the
voltage difference between the sope chassis and the record player
chassis,
but I didn't think to. I'll have to do that. Perhaps he chassis is
live. I
didn't think this would be the case though, since there is a cap with

the


negative connected to the case, as well as a few other green wires.


That capacitor might be leaking or (worse) shorted. It can be a lethal
failure (I read just this week about a minister in Waco who was
electrocuted during a baptism when he grabbed a microphone that was
"hot."). Be careful.


Here's a cite to that story:
http://www.cbsnews.com/stories/2005/...in995829.shtml



Thanks


"Asimov" wrote in
message
news:MSGID_1=3a167=2f133.0_43612958@fidonet. org...
"tempus fugit" bravely wrote to "All" (27 Oct 05 11:17:42)
--- on the heady topic of "unit hums loudly regardless of volume"

tf From: "tempus fugit"
tf Xref: core-easynews sci.electronics.repair:346437

tf Hey all;

tf I'm trying to repair an old tube portable record player. When it

is


tf on, it hums really loud, regardless of the volume.

Have you tried turning the ac plug around?

Which way the plug is inserted matters with these. Let the record
player warm up, then insert the plug one way or the other, and then
paint a mark for which was the quietest way. One way: lots of hum, the
other: quiet hiss.

Those old tube units used to get B+ directly from the powerline (or
sometimes a voltage doubler) and used a large value resistor bypassed
by a 0.01uF to RF ground the tone arm shielding to neutral. The power
for the filaments often came from a secondary winding in the motor
coil. Don't use this type of record player near the bathtub. Lethal!

Another possibility is a broken wire at the cartridge.

A*s*i*m*o*v

... Just a little force field zap.




--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .




--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .





--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

Hi...

Sorry for the top posting; but the rest is getting a bit
convulted with a confusing mixture

Just wondering... has tempus or any of the rest of you other
old timers considered the possibility that it might be a dc
"choke" speaker?

Take care.

Ken



CJT wrote:

tempus fugit wrote:

We're talking about a capacitor between the chassis and one side
of the line, right?



I havent reopened the chassis, but it seems to be connected between the
ground of the speaker and the chassis.


OK, that's something totally different.



something is shorted somehwere else. Oh, and I checked the voltage


between

the record player chassis and the scope chassis - 120VAC


Reversing the plug in the wall socket should change that (but don't
count on it).



Reversing the plug did correct that. Is this a design shortcoming (if so,
there's gotta be a safer way to set that up) or should I be looking for a
fault somewhere?


That's normal for a "hot chassis" device. But such a device won't have
a power transformer, and I thought you said this one did. Could you be
confusing an output transformer with a power transformer?

If you are (and I suspect you are) then you are such a newbie that you
had better stop now and enlist the help of somebody who knows what
they're doing before you kill yourself. No kidding. I don't want to
have anything more to do with this pursuit.

tempus may fugit, but not for the dead



You really need to be careful with this device. I can't stress that
enough. Death is not to be trifled with.



I am being very careful, not to worry, but I appreciate your concern and
helpful advice (including those on personal safety).

Thanks again


Thanks


"CJT" wrote in message
...


CJT wrote:



tempus fugit wrote:



Tried the turining around the plug trick, but it made no
difference. I
also
disconnected the phono plug that connects the tone arm to the amp


unit,

which also made no difference.

Here is something curious though. I accidentally touched my scope
while my
hand was on the record player chassis and got a fairly good
shock. The
scope
has a 3 prong AC plug (the record player doesn't). I should've
measured the
voltage difference between the sope chassis and the record player
chassis,
but I didn't think to. I'll have to do that. Perhaps he chassis is
live. I
didn't think this would be the case though, since there is a cap
with


the


negative connected to the case, as well as a few other green wires.


That capacitor might be leaking or (worse) shorted. It can be a
lethal
failure (I read just this week about a minister in Waco who was
electrocuted during a baptism when he grabbed a microphone that was
"hot."). Be careful.


Here's a cite to that story:
http://www.cbsnews.com/stories/2005/...in995829.shtml



Thanks


"Asimov" wrote in
message
...
"tempus fugit" bravely wrote to "All" (27 Oct 05 11:17:42)
--- on the heady topic of "unit hums loudly regardless of volume"

tf From: "tempus fugit"
tf Xref: core-easynews sci.electronics.repair:346437

tf Hey all;

tf I'm trying to repair an old tube portable record player. When it


is


tf on, it hums really loud, regardless of the volume.

Have you tried turning the ac plug around?

Which way the plug is inserted matters with these. Let the record
player warm up, then insert the plug one way or the other, and then
paint a mark for which was the quietest way. One way: lots of
hum, the
other: quiet hiss.

Those old tube units used to get B+ directly from the powerline (or
sometimes a voltage doubler) and used a large value resistor
bypassed
by a 0.01uF to RF ground the tone arm shielding to neutral. The
power
for the filaments often came from a secondary winding in the motor
coil. Don't use this type of record player near the bathtub. Lethal!

Another possibility is a broken wire at the cartridge.

A*s*i*m*o*v

... Just a little force field zap.




--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .





--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

Ken Weitzel wrote:


Hi...

Sorry for the top posting; but the rest is getting a bit
convulted with a confusing mixture

Just wondering... has tempus or any of the rest of you other
old timers considered the possibility that it might be a dc
"choke" speaker?

That's an interesting possibility I hadn't thought of.
I haven't seen one of those in quite a few years. Did
they even make portables before PM speakers became the norm?


Take care.

Ken



CJT wrote:

tempus fugit wrote:

We're talking about a capacitor between the chassis and one side
of the line, right?




I havent reopened the chassis, but it seems to be connected between the
ground of the speaker and the chassis.



OK, that's something totally different.



something is shorted somehwere else. Oh, and I checked the voltage



between

the record player chassis and the scope chassis - 120VAC



Reversing the plug in the wall socket should change that (but don't
count on it).




Reversing the plug did correct that. Is this a design shortcoming (if
so,
there's gotta be a safer way to set that up) or should I be looking
for a
fault somewhere?


That's normal for a "hot chassis" device. But such a device won't have
a power transformer, and I thought you said this one did. Could you be
confusing an output transformer with a power transformer?

If you are (and I suspect you are) then you are such a newbie that you
had better stop now and enlist the help of somebody who knows what
they're doing before you kill yourself. No kidding. I don't want to
have anything more to do with this pursuit.

tempus may fugit, but not for the dead



You really need to be careful with this device. I can't stress that
enough. Death is not to be trifled with.




I am being very careful, not to worry, but I appreciate your concern and
helpful advice (including those on personal safety).

Thanks again


Thanks


"CJT" wrote in message
...


CJT wrote:



tempus fugit wrote:



Tried the turining around the plug trick, but it made no
difference. I
also
disconnected the phono plug that connects the tone arm to the amp



unit,

which also made no difference.

Here is something curious though. I accidentally touched my scope
while my
hand was on the record player chassis and got a fairly good
shock. The
scope
has a 3 prong AC plug (the record player doesn't). I should've
measured the
voltage difference between the sope chassis and the record player
chassis,
but I didn't think to. I'll have to do that. Perhaps he chassis is
live. I
didn't think this would be the case though, since there is a cap
with



the


negative connected to the case, as well as a few other green wires.


That capacitor might be leaking or (worse) shorted. It can be a
lethal
failure (I read just this week about a minister in Waco who was
electrocuted during a baptism when he grabbed a microphone that was
"hot."). Be careful.


Here's a cite to that story:
http://www.cbsnews.com/stories/2005/...in995829.shtml



Thanks


"Asimov" wrote in
message
...
"tempus fugit" bravely wrote to "All" (27 Oct 05 11:17:42)
--- on the heady topic of "unit hums loudly regardless of volume"

tf From: "tempus fugit"
tf Xref: core-easynews sci.electronics.repair:346437

tf Hey all;

tf I'm trying to repair an old tube portable record player.
When it



is


tf on, it hums really loud, regardless of the volume.

Have you tried turning the ac plug around?

Which way the plug is inserted matters with these. Let the record
player warm up, then insert the plug one way or the other, and then
paint a mark for which was the quietest way. One way: lots of
hum, the
other: quiet hiss.

Those old tube units used to get B+ directly from the powerline (or
sometimes a voltage doubler) and used a large value resistor
bypassed
by a 0.01uF to RF ground the tone arm shielding to neutral. The
power
for the filaments often came from a secondary winding in the motor
coil. Don't use this type of record player near the bathtub.
Lethal!

Another possibility is a broken wire at the cartridge.

A*s*i*m*o*v

... Just a little force field zap.




--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .






--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .










--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

What about the 3 or 4 section electrolytic usually at 150 volts that comes
from the main rectifier usually being a tube.


"CJT" wrote in message
...
Ken Weitzel wrote:


Hi...

Sorry for the top posting; but the rest is getting a bit
convulted with a confusing mixture

Just wondering... has tempus or any of the rest of you other
old timers considered the possibility that it might be a dc
"choke" speaker?

That's an interesting possibility I hadn't thought of.
I haven't seen one of those in quite a few years. Did
they even make portables before PM speakers became the norm?


Take care.

Ken



CJT wrote:

tempus fugit wrote:

We're talking about a capacitor between the chassis and one side
of the line, right?




I havent reopened the chassis, but it seems to be connected between the
ground of the speaker and the chassis.



OK, that's something totally different.



something is shorted somehwere else. Oh, and I checked the voltage



between

the record player chassis and the scope chassis - 120VAC



Reversing the plug in the wall socket should change that (but don't
count on it).




Reversing the plug did correct that. Is this a design shortcoming (if
so,
there's gotta be a safer way to set that up) or should I be looking for
a
fault somewhere?


That's normal for a "hot chassis" device. But such a device won't have
a power transformer, and I thought you said this one did. Could you be
confusing an output transformer with a power transformer?

If you are (and I suspect you are) then you are such a newbie that you
had better stop now and enlist the help of somebody who knows what
they're doing before you kill yourself. No kidding. I don't want to
have anything more to do with this pursuit.

tempus may fugit, but not for the dead



You really need to be careful with this device. I can't stress that
enough. Death is not to be trifled with.




I am being very careful, not to worry, but I appreciate your concern
and
helpful advice (including those on personal safety).

Thanks again


Thanks


"CJT" wrote in message
...


CJT wrote:



tempus fugit wrote:



Tried the turining around the plug trick, but it made no
difference. I
also
disconnected the phono plug that connects the tone arm to the amp



unit,

which also made no difference.

Here is something curious though. I accidentally touched my scope
while my
hand was on the record player chassis and got a fairly good shock.
The
scope
has a 3 prong AC plug (the record player doesn't). I should've
measured the
voltage difference between the sope chassis and the record player
chassis,
but I didn't think to. I'll have to do that. Perhaps he chassis is
live. I
didn't think this would be the case though, since there is a cap
with



the


negative connected to the case, as well as a few other green
wires.


That capacitor might be leaking or (worse) shorted. It can be a
lethal
failure (I read just this week about a minister in Waco who was
electrocuted during a baptism when he grabbed a microphone that was
"hot."). Be careful.


Here's a cite to that story:
http://www.cbsnews.com/stories/2005/...in995829.shtml



Thanks


"Asimov" wrote in
message
...
"tempus fugit" bravely wrote to "All" (27 Oct 05 11:17:42)
--- on the heady topic of "unit hums loudly regardless of volume"

tf From: "tempus fugit"
tf Xref: core-easynews sci.electronics.repair:346437

tf Hey all;

tf I'm trying to repair an old tube portable record player. When
it



is


tf on, it hums really loud, regardless of the volume.

Have you tried turning the ac plug around?

Which way the plug is inserted matters with these. Let the record
player warm up, then insert the plug one way or the other, and
then
paint a mark for which was the quietest way. One way: lots of hum,
the
other: quiet hiss.

Those old tube units used to get B+ directly from the powerline
(or
sometimes a voltage doubler) and used a large value resistor
bypassed
by a 0.01uF to RF ground the tone arm shielding to neutral. The
power
for the filaments often came from a secondary winding in the motor
coil. Don't use this type of record player near the bathtub.
Lethal!

Another possibility is a broken wire at the cartridge.

A*s*i*m*o*v

... Just a little force field zap.




--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .






--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .










--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

Thanks again for your reply.

I'll have to pop the chassis again to see about the power transformer thing.
It is possible that the xformer I saw (there is 1 outside the chassis) is an
output and not a power xformer. I don't remember if there was one inside the
chassis or not. Bear in mind that I just took a quick look at the thing,
checked the caps real quick (as I suspected them to be the problem) and put
it back together. There is no PC board, just flying wires everywhere, which
I didnt trace any of. I'll take a closer look to see exactly what is
connected where and post back here with the results.


"CJT" wrote in message
...
tempus fugit wrote:

We're talking about a capacitor between the chassis and one side
of the line, right?


I havent reopened the chassis, but it seems to be connected between the
ground of the speaker and the chassis.

OK, that's something totally different.



something is shorted somehwere else. Oh, and I checked the voltage

between

the record player chassis and the scope chassis - 120VAC

Reversing the plug in the wall socket should change that (but don't
count on it).


Reversing the plug did correct that. Is this a design shortcoming (if
so,
there's gotta be a safer way to set that up) or should I be looking for
a
fault somewhere?


That's normal for a "hot chassis" device. But such a device won't have
a power transformer, and I thought you said this one did. Could you be
confusing an output transformer with a power transformer?

If you are (and I suspect you are) then you are such a newbie that you
had better stop now and enlist the help of somebody who knows what
they're doing before you kill yourself. No kidding. I don't want to
have anything more to do with this pursuit.

tempus may fugit, but not for the dead



You really need to be careful with this device. I can't stress that
enough. Death is not to be trifled with.


I am being very careful, not to worry, but I appreciate your concern and
helpful advice (including those on personal safety).

Thanks again


Thanks


"CJT" wrote in message
...


CJT wrote:



tempus fugit wrote:



Tried the turining around the plug trick, but it made no difference.
I
also
disconnected the phono plug that connects the tone arm to the amp

unit,

which also made no difference.

Here is something curious though. I accidentally touched my scope
while my
hand was on the record player chassis and got a fairly good shock.
The
scope
has a 3 prong AC plug (the record player doesn't). I should've
measured the
voltage difference between the sope chassis and the record player
chassis,
but I didn't think to. I'll have to do that. Perhaps he chassis is
live. I
didn't think this would be the case though, since there is a cap
with

the


negative connected to the case, as well as a few other green wires.


That capacitor might be leaking or (worse) shorted. It can be a
lethal
failure (I read just this week about a minister in Waco who was
electrocuted during a baptism when he grabbed a microphone that was
"hot."). Be careful.


Here's a cite to that story:
http://www.cbsnews.com/stories/2005/...in995829.shtml



Thanks


"Asimov" wrote in
message
news:MSGID_1=3a167=2f133.0_43612958@fidonet. org...
"tempus fugit" bravely wrote to "All" (27 Oct 05 11:17:42)
--- on the heady topic of "unit hums loudly regardless of volume"

tf From: "tempus fugit"
tf Xref: core-easynews sci.electronics.repair:346437

tf Hey all;

tf I'm trying to repair an old tube portable record player. When it

is


tf on, it hums really loud, regardless of the volume.

Have you tried turning the ac plug around?

Which way the plug is inserted matters with these. Let the record
player warm up, then insert the plug one way or the other, and then
paint a mark for which was the quietest way. One way: lots of hum,
the
other: quiet hiss.

Those old tube units used to get B+ directly from the powerline (or
sometimes a voltage doubler) and used a large value resistor
bypassed
by a 0.01uF to RF ground the tone arm shielding to neutral. The
power
for the filaments often came from a secondary winding in the motor
coil. Don't use this type of record player near the bathtub. Lethal!

Another possibility is a broken wire at the cartridge.

A*s*i*m*o*v

... Just a little force field zap.




--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .




--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .





--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

tempus fugit wrote:
: Hey all;

: I'm trying to repair an old tube portable record player. When it is on, it
: hums really loud, regardless of the volume. I assumed that this must be a
: problem with filter caps, but they test OK for ESR and shorts. 1 of the
: problems is that there are 3 or 4 in a can, so I don't know what the values
: are supposed to be.

: Is there anything else that may cause this symptom? I suppose I could
: parallel some caps across the existing ones, but I don't even know what the
: values are supposed to be.

: Thanks


I fixed an old record player with the same problem and I used to be a TV
repair tech.

I'd bet money on a bad filter capacitor. Just replace it with something
of the same voltage rating and equal capacitance or slightly higher if the
exact value isn't available.

It's not something w/the tone arm because that would vary with volume.
It's not a shorted diode because if it were, it'd be putting AC in
to the capacitor and that would be an AC short and a destructive overcurrent
situation would result. It's not an open diode because you'd get no hum
if that were the case.

Replace the filter capacitor. They're usually a tab mounted can and it'll
be difficult to find one like it so instead, use an axial leaded capacitor
and run insulated wires to it and glue it somewhere to keep it in place
(silicone cauking/sealant would do the trick).

b.

tempus fugit wrote:
: Hey all;

: I'm trying to repair an old tube portable record player. When it is on, it
: hums really loud, regardless of the volume. I assumed that this must be a
: problem with filter caps, but they test OK for ESR and shorts. 1 of the
: problems is that there are 3 or 4 in a can, so I don't know what the values
: are supposed to be.

Sorry for another followup.

The capacitor is a multi-section capacitor. Their values are usually
stamped or imprinted on the side of the can. The leads will usually have
a triangle, half circle and square markings/openings in the phenolic part
of the capacitor (bottom). The "legend" of values will usually show that
on the capacitor markings.

If you can't get the replacement, you can wire up individual electrolytic
capacitora and tie all of the minus sides of the wires together and ground this
to what was previously the capacitor can ground and use the + lead of each
capacitor to connect the the wires that previously attached to the
capacitors.

Here are a few sites relating to them:
http://www.dialcover.com/caps.html
http://www.partsexpress.com/webpage....Gro up_ID=557
http://www.kenselectronics.com/lists/caps.htm
https://secure.tubesandmore.com/

barry

thanks for the reply Barry;

The cap is indeed multi section - I think there are 4 different caps.
Unfortunately it is a cardboard container with no visible values. I'll look
a little closer and see what I can see.

Thanks



wrote in message
oups.com...
tempus fugit wrote:
: Hey all;

: I'm trying to repair an old tube portable record player. When it is on,
it
: hums really loud, regardless of the volume. I assumed that this must be
a
: problem with filter caps, but they test OK for ESR and shorts. 1 of the
: problems is that there are 3 or 4 in a can, so I don't know what the
values
: are supposed to be.

Sorry for another followup.

The capacitor is a multi-section capacitor. Their values are usually
stamped or imprinted on the side of the can. The leads will usually have
a triangle, half circle and square markings/openings in the phenolic part
of the capacitor (bottom). The "legend" of values will usually show that
on the capacitor markings.

If you can't get the replacement, you can wire up individual electrolytic
capacitora and tie all of the minus sides of the wires together and ground
this
to what was previously the capacitor can ground and use the + lead of each
capacitor to connect the the wires that previously attached to the
capacitors.

Here are a few sites relating to them:
http://www.dialcover.com/caps.html

http://www.partsexpress.com/webpage....Gro up_ID=557
http://www.kenselectronics.com/lists/caps.htm
https://secure.tubesandmore.com/

barry

Hello tempus, are you still with us? Don't forget to pull the plug, eh!
I suggest you search for a brand and model #, then search at
rec.antiques.radio+phono, where there are expert advisors on how these
units can be fixed. The transformer you saw was for the output to the
speaker. You are dealing with a live chassis unit. the "death cap" may
be shorted, and the hum you here is 120vac running thru the chassis.
The filter caps may not be too bad, although they are always leaky at
that age. You can use 50-80 uF for the first 2, then drop to 20-30 for
the other 2. There is no diode tube to worry about. If the diode is a
bunch of square plates with a central bolt, it is selenium. Replace it
with a new silicon diode and a resistor. Cheers.

John Kogel

Still alive and kicking John, lol.

Thanks for the tips. The "death cap" I assume is the one that is connected
from the live to the chassis? I'm not sure that there even is one in this
unit, but as I mentioned earlier, I just took a quick peek inside the
chassis and put it back together. I haven't had too much time to mess with
it, but I'll definitely look for that when I do. If everyone would like, I
could take a picture of it and post it on ABSE.

What do youy think?

Thanks again
"Porky" wrote in message
oups.com...
Hello tempus, are you still with us? Don't forget to pull the plug, eh!
I suggest you search for a brand and model #, then search at
rec.antiques.radio+phono, where there are expert advisors on how these
units can be fixed. The transformer you saw was for the output to the
speaker. You are dealing with a live chassis unit. the "death cap" may
be shorted, and the hum you here is 120vac running thru the chassis.
The filter caps may not be too bad, although they are always leaky at
that age. You can use 50-80 uF for the first 2, then drop to 20-30 for
the other 2. There is no diode tube to worry about. If the diode is a
bunch of square plates with a central bolt, it is selenium. Replace it
with a new silicon diode and a resistor. Cheers.

John Kogel

tempus fugit
Still alive and kicking John, lol.

The "death cap" I assume is the one that is connected
from the live to the chassis? I'm not sure that there even is one in this
unit,

Yes, there is often a .05 or so cap from live to chassis on
transformerless tube gear. It's main purpose is to turn the chassis
into a sheild to keep radio interference.from being detected by the
device. It's secondary function is to shock the @@#$ out of you when it
shorts, (although they are rated at 600v and don't carry much current,
so failures are usually due to moisture and disuse).
If you have small kids, keep them away from the thing. After it is
fixed, install an isolation transformer for $30. Yuo can even build
your own by connecting 2 12V trannys back-to-back. This isolates the
voltages in the chassis from those in your house = no more shocks.
Cheers.

JK

Thanks JK.

I got a chance to take a closer look at this thing and the neutral wire is
connected to ground, but there appears to be about 200 ohms of resistance
between the ground on the filter cap and the chassis. I didn't see anywhere
were the live wire was connected to the chassis through a cap. Forgetting
about the hum for a second (I'd like to make this whole thing a little safer
1st) would a quick fix for the 120v I've seen on the chassis be to simply
install a polarized plug on the power cord? This way I could ensure that it
was never plugged in backwards thus connecting the chassis to the live 120v
line.

Also, I mentioned a small blue thing that looks like a bunch of thin squares
stacked on top of one another, that someone suggested was a selenium
rectifier. I hear they emit a poison gas when they burn. Would it emit any
dangerous gases during normal operation? Should I make replacing this part a
priority? I should also mention that there is 1 tab on this piece that has
some solder on it but no wires or anything connected to it. Could this be
the source of my hum problems?

Thanks again

"Porky" wrote in message
oups.com...
tempus fugit
Still alive and kicking John, lol.

The "death cap" I assume is the one that is connected
from the live to the chassis? I'm not sure that there even is one in this
unit,

Yes, there is often a .05 or so cap from live to chassis on
transformerless tube gear. It's main purpose is to turn the chassis
into a sheild to keep radio interference.from being detected by the
device. It's secondary function is to shock the @@#$ out of you when it
shorts, (although they are rated at 600v and don't carry much current,
so failures are usually due to moisture and disuse).
If you have small kids, keep them away from the thing. After it is
fixed, install an isolation transformer for $30. Yuo can even build
your own by connecting 2 12V trannys back-to-back. This isolates the
voltages in the chassis from those in your house = no more shocks.
Cheers.

JK

hum regardless of volume usually means bad or dried up electrolytic filter
cap(s) and/or maybe a bad rectifier..... and no, during normal proper
operation the selenium rectifiers do not emit poison gas. I would just
simply bridge the filter cap with a replacement of the same or approximate
value and the same or higher voltage to see if the hum goes away.... which
it probably will given the symptoms you reported.
- - - - - - - - - -


"tempus fugit" wrote in message
...
Thanks JK.

I got a chance to take a closer look at this thing and the neutral wire is
connected to ground, but there appears to be about 200 ohms of resistance
between the ground on the filter cap and the chassis. I didn't see
anywhere
were the live wire was connected to the chassis through a cap. Forgetting
about the hum for a second (I'd like to make this whole thing a little
safer
1st) would a quick fix for the 120v I've seen on the chassis be to simply
install a polarized plug on the power cord? This way I could ensure that
it
was never plugged in backwards thus connecting the chassis to the live
120v
line.

Also, I mentioned a small blue thing that looks like a bunch of thin
squares
stacked on top of one another, that someone suggested was a selenium
rectifier. I hear they emit a poison gas when they burn. Would it emit any
dangerous gases during normal operation? Should I make replacing this part
a
priority? I should also mention that there is 1 tab on this piece that has
some solder on it but no wires or anything connected to it. Could this be
the source of my hum problems?

Thanks again

"Porky" wrote in message
oups.com...
tempus fugit
Still alive and kicking John, lol.

The "death cap" I assume is the one that is connected
from the live to the chassis? I'm not sure that there even is one in
this
unit,

Yes, there is often a .05 or so cap from live to chassis on
transformerless tube gear. It's main purpose is to turn the chassis
into a sheild to keep radio interference.from being detected by the
device. It's secondary function is to shock the @@#$ out of you when it
shorts, (although they are rated at 600v and don't carry much current,
so failures are usually due to moisture and disuse).
If you have small kids, keep them away from the thing. After it is
fixed, install an isolation transformer for $30. Yuo can even build
your own by connecting 2 12V trannys back-to-back. This isolates the
voltages in the chassis from those in your house = no more shocks.
Cheers.

JK

Thanks for your reply Sofie.

I agree with your diagnosis - this reeks of a bad filter cap. The problem is
that the filter cap is an old cardboard multisection with no marks of any
kind on it. There are 4 tabs on the bottom, with the twistlocks acting as
grounds (I think). Of those tabs, 1 shows a 300 or so ohm resistance to one
of the twistlocks. Assuiming that that tab is a cap +, and not a ground,
that cap definitely needs replacing. What I'd like to do is just replace the
lot, but I have no way of knowing what the values of each of the 4 tabs are
supposed to be. Would just replacing them all with, say, 22uF caps be OK?

I'd like to replace the rectifier as well, but I need to figure how to set
up a bridge or diodes properly in the place of the old one. I've never seen
one of these before, but it has 2 tabs on it - + and (-). The (-) tab
acually has nothing connected to it. You can see that it once did, but
doesn't anymore. So..... I'll have to try to figure out where it should have
been connected at one time. Oddly, there is about 150V DC across the filter
caps.

Thanks again



"sofie" wrote in message
...
hum regardless of volume usually means bad or dried up electrolytic filter
cap(s) and/or maybe a bad rectifier..... and no, during normal proper
operation the selenium rectifiers do not emit poison gas. I would just
simply bridge the filter cap with a replacement of the same or approximate
value and the same or higher voltage to see if the hum goes away.... which
it probably will given the symptoms you reported.
- - - - - - - - - -


"tempus fugit" wrote in message
...
Thanks JK.

I got a chance to take a closer look at this thing and the neutral wire
is
connected to ground, but there appears to be about 200 ohms of
resistance
between the ground on the filter cap and the chassis. I didn't see
anywhere
were the live wire was connected to the chassis through a cap.
Forgetting
about the hum for a second (I'd like to make this whole thing a little
safer
1st) would a quick fix for the 120v I've seen on the chassis be to
simply
install a polarized plug on the power cord? This way I could ensure that
it
was never plugged in backwards thus connecting the chassis to the live
120v
line.

Also, I mentioned a small blue thing that looks like a bunch of thin
squares
stacked on top of one another, that someone suggested was a selenium
rectifier. I hear they emit a poison gas when they burn. Would it emit
any
dangerous gases during normal operation? Should I make replacing this
part
a
priority? I should also mention that there is 1 tab on this piece that
has
some solder on it but no wires or anything connected to it. Could this
be
the source of my hum problems?

Thanks again

"Porky" wrote in message
oups.com...
tempus fugit
Still alive and kicking John, lol.

The "death cap" I assume is the one that is connected
from the live to the chassis? I'm not sure that there even is one in
this
unit,

Yes, there is often a .05 or so cap from live to chassis on
transformerless tube gear. It's main purpose is to turn the chassis
into a sheild to keep radio interference.from being detected by the
device. It's secondary function is to shock the @@#$ out of you when
it
shorts, (although they are rated at 600v and don't carry much current,
so failures are usually due to moisture and disuse).
If you have small kids, keep them away from the thing. After it is
fixed, install an isolation transformer for $30. Yuo can even build
your own by connecting 2 12V trannys back-to-back. This isolates the
voltages in the chassis from those in your house = no more shocks.
Cheers.

JK

150vdc across the filter cap is exactly what you should expect.... as my
previous reply suggested, you can quickly and easily bridge the first
section right after the rectifier of that old multi-section cap with just
about any thing you have laying around with a rating of at least 150 vdc and
a capacitance of 20 to 60MFD... this is not very critical and will instantly
confirm the diagnosis.... so stop guessing here and get a temporary cap
bridged across the old one so you can go forward with the repair.
More than likely all the sections are bad and can all be bridged (usually
not very critical capacitance values) if you want to leave the old one in
place... in fact, as long as it is not shorted or electrically leaking then
you can leave all the connections in place and just neatly install new,
usually smaller, replacement caps under the chassis.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


snipped:
"tempus fugit" wrote in message
Thanks for your reply Sofie.

I agree with your diagnosis - this reeks of a bad filter cap. The problem
is
that the filter cap is an old cardboard multisection with no marks of any
kind on it. There are 4 tabs on the bottom, with the twistlocks acting as
grounds (I think). Of those tabs, 1 shows a 300 or so ohm resistance to
one
of the twistlocks. Assuiming that that tab is a cap +, and not a ground,
that cap definitely needs replacing. What I'd like to do is just replace
the
lot, but I have no way of knowing what the values of each of the 4 tabs
are
supposed to be. Would just replacing them all with, say, 22uF caps be OK?

Hello tempus. I've been away but so have you. From your last post, more
clues are taking shape as to how to fix your phono. We need to know
what power tube is in it. It will have either 8 pins, (25, 35 or 50L6)
making it an early model, or a later model 9-pin 50C5 or 50EH5. Locate
the pin for the plate, on the 50EH5 or 50C5 that is pin 7, looking at
the bottom of the socket and counting clockwise from the gap. On the
8-pin (octal) tube the plate is on pin 3, clockwise from the notch. The
1st filter cap connects to this pin. It is likely a 40 uF rated for no
less than 150 v. You can use up to 80 uF here and use a high voltage
rating like the 400 v units for safety. The next filter cap connects to
pin 5 or 6 I'm not entirely sure but you can trace the wire back to the
multicap. It should also be a 40 uF (50 - 80 uF will work). For third
cap going to pin 1 or 6 of the 12AX7, a lower value like 22 uF may be
alright. The 4th cap should be 22 uFif it runs to the cathode, pin 1 on
the 9-pin or pin 8 of the octal, or the 12AX7, pin 3 or 8. For these
last 2 caps, 150 v rating is OK.

It appears the selenium rectifier has been bypassed already. There is a
solid state diode doing the job. It is likely black with a silver band
but they do come in other colors, looks like a resistor but with only
one band. Ideally, a resistor is included in series with the diode to
bring the voltage down a little to the level of the original.

The shock you recieved could very likey be due to the filter cap
shorting to ground, and replacing all the caps in the multi-cap can
will likely solve both shock and hum problems. A polarized cord is a
very good idea. A 3-prong cord is even better, with the green wire
going to a solid ground point on the chassis. If you ground the
chassis, locate the death cap, (line to chassis cap @ +/- 0.05 uF), and
clip it out of there to prevent future shocks.

BTW, the tube heater supply is likely fed by a tap on the motor
winding, eliminating the need for a separate tranformer. This ain't
hi-fi. Take good care of that pickup cartridge.

JK

Thanks again for the replies guys.

Yet more information:

The power tube is a 50L6. The selenium rectifier has been bypasssed by a
single top hat diode (I guess I was looking for a bridge, or at least 2
diodes).

I tried to rewire the power cord, and I'm getting frustrated. I wired it
correctly, so that the hot lead went to the switch. This put 120v on the
chassis, though so I switched it around. Guess what?? Still 120v on the
chassis. This is with the power off. Before I put the new cable in,
switching the plug around took the 120v off the chassis. The weird thing is
that I can't locate any place where either wire is connected to the chassis,
and there doesn't seem to be a death cap.

Sorry about the infrequency of the replies, but I don't get a lot of free
time to work on it.
Thanks


"Porky" wrote in message
oups.com...
Hello tempus. I've been away but so have you. From your last post, more
clues are taking shape as to how to fix your phono. We need to know
what power tube is in it. It will have either 8 pins, (25, 35 or 50L6)
making it an early model, or a later model 9-pin 50C5 or 50EH5. Locate
the pin for the plate, on the 50EH5 or 50C5 that is pin 7, looking at
the bottom of the socket and counting clockwise from the gap. On the
8-pin (octal) tube the plate is on pin 3, clockwise from the notch. The
1st filter cap connects to this pin. It is likely a 40 uF rated for no
less than 150 v. You can use up to 80 uF here and use a high voltage
rating like the 400 v units for safety. The next filter cap connects to
pin 5 or 6 I'm not entirely sure but you can trace the wire back to the
multicap. It should also be a 40 uF (50 - 80 uF will work). For third
cap going to pin 1 or 6 of the 12AX7, a lower value like 22 uF may be
alright. The 4th cap should be 22 uFif it runs to the cathode, pin 1 on
the 9-pin or pin 8 of the octal, or the 12AX7, pin 3 or 8. For these
last 2 caps, 150 v rating is OK.

It appears the selenium rectifier has been bypassed already. There is a
solid state diode doing the job. It is likely black with a silver band
but they do come in other colors, looks like a resistor but with only
one band. Ideally, a resistor is included in series with the diode to
bring the voltage down a little to the level of the original.

The shock you recieved could very likey be due to the filter cap
shorting to ground, and replacing all the caps in the multi-cap can
will likely solve both shock and hum problems. A polarized cord is a
very good idea. A 3-prong cord is even better, with the green wire
going to a solid ground point on the chassis. If you ground the
chassis, locate the death cap, (line to chassis cap @ +/- 0.05 uF), and
clip it out of there to prevent future shocks.

BTW, the tube heater supply is likely fed by a tap on the motor
winding, eliminating the need for a separate tranformer. This ain't
hi-fi. Take good care of that pickup cartridge.

JK

When in doubt, use 33uF or so, @450V (22uF is OK for a start. If the
hum reduces but does not go away altogether, then go up). Otherwise,
200uF @20V or so for LV stuff.

Bridge: Voltage in X 1.4142 = voltage out.
Single diode: Voltage in .7071 = voltage out.

Keep that in mind.

Peter Wieck
Wyncote, PA

"tempus fugit" bravely wrote to "All" (13 Nov 05 22:07:08)
--- on the heady topic of " unit hums loudly regardless of volume"

tf From: "tempus fugit"
tf Xref: core-easynews sci.electronics.repair:348490

tf Thanks again for the replies guys.

tf Yet more information:

tf The power tube is a 50L6. The selenium rectifier has been bypasssed by
tf a single top hat diode (I guess I was looking for a bridge, or at least
tf 2 diodes).

High voltage and low current allows using only halfwave rectification.


tf I tried to rewire the power cord, and I'm getting frustrated. I wired
tf it correctly, so that the hot lead went to the switch. This put 120v on
tf the chassis, though so I switched it around. Guess what?? Still 120v on
tf the chassis. This is with the power off. Before I put the new cable in,
tf switching the plug around took the 120v off the chassis. The weird
tf thing is that I can't locate any place where either wire is connected
tf to the chassis, and there doesn't seem to be a death cap.

There is usually a 1meg or 470K resistor with a disc cap across it.

BTW The dmm has 10M high-Z input and will read full 120V no matter
where the line connects. It's safer connecting line to the rectifier
circuit not the chassis. The 120V on the chassis should then be high
impedance and not a widow maker. Load the dmm input with 10K to test,
if it measures more than 50V then there is a serious problem.

A*s*i*m*o*v

.... Real techs don't lick nine-volt batteries!

Thanks again for the replies.

I solved the 120V on the chassis mystery - the new cord I installed wasn't
polarized after all. It has a white stripe on it (black cable) and one of
the tips appeared bigger than the other, but it would fit in the socket
either way. I installed an actual polarized cord and the chassis is AC free.

Hopefully I'll get to the caps soon. I'll keep you posted.

Thanks


wrote in message
oups.com...
When in doubt, use 33uF or so, @450V (22uF is OK for a start. If the
hum reduces but does not go away altogether, then go up). Otherwise,
200uF @20V or so for LV stuff.

Bridge: Voltage in X 1.4142 = voltage out.
Single diode: Voltage in .7071 = voltage out.

Keep that in mind.

Peter Wieck
Wyncote, PA