I tried to re-cap a tube receiver (amplifier + tuner), and now when I turn it
on it starts playing music for a few seconds after it warms up, then the music
fades out and and hum takes over. I don't really know what I'm doing, and the
wiring inside looks like a mess of spaghetti. I'm pretty sure I replaced the
caps properly, but I used .068uf WIMA caps to replace .050uf wax/paper caps,
and I'm wondering if the value difference, added up over 8 caps would make a
difference? Other than that, does anyone have any advice based on my
description of the unit's behavior? Any comments whatsoever might be helpful..

Derwin wrote:

I tried to re-cap a tube receiver (amplifier + tuner), and now when I turn it
on it starts playing music for a few seconds after it warms up, then the music
fades out and and hum takes over. I don't really know what I'm doing, and the
wiring inside looks like a mess of spaghetti. I'm pretty sure I replaced the
caps properly, but I used .068uf WIMA caps to replace .050uf wax/paper caps,
and I'm wondering if the value difference, added up over 8 caps would make a
difference? Other than that, does anyone have any advice based on my
description of the unit's behavior? Any comments whatsoever might be helpful..


Try news:rec.antiques.radio+phono That is why the group was created.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

"Derwin" wrote in message
news:6mzYh.5305$Dq6.3498@edtnps82...

I tried to re-cap a tube receiver (amplifier + tuner), and now when I turn
it
on it starts playing music for a few seconds after it warms up, then the
music
fades out and and hum takes over. I don't really know what I'm doing, and
the
wiring inside looks like a mess of spaghetti. I'm pretty sure I replaced
the
caps properly, but I used .068uf WIMA caps to replace .050uf wax/paper
caps,
and I'm wondering if the value difference, added up over 8 caps would make
a
difference?

No.

Other than that, does anyone have any advice based on my
description of the unit's behavior? Any comments whatsoever might be
helpful..

At this point you need to fault find. Does it work OK with tape or other
music input?

In article ,
l says...

On Sat, 28 Apr 2007 04:02:09 +0000, Homer J Simpson wrote:


"Derwin" wrote in message
news:6mzYh.5305$Dq6.3498@edtnps82...

I tried to re-cap a tube receiver (amplifier + tuner), and now when I turn
it
on it starts playing music for a few seconds after it warms up, then the
music
fades out and and hum takes over. I don't really know what I'm doing, and
the
wiring inside looks like a mess of spaghetti. I'm pretty sure I replaced
the
caps properly, but I used .068uf WIMA caps to replace .050uf wax/paper
caps,
and I'm wondering if the value difference, added up over 8 caps would make
a
difference?

No.

Other than that, does anyone have any advice based on my
description of the unit's behavior? Any comments whatsoever might be
helpful..

At this point you need to fault find. Does it work OK with tape or other
music input?

I wouldn't delve that far, sounds like a PS/PA problem. The OP is confused
man, he said it looks like spaghetti.


Wow, I was expecting a higher calibre of responses. I'll look into that
rec.antiques.radio+phono group...

What exactly do you have against spaghetti, anyway? Is it a racist thing about
italians, or?

In article 5HzYh.5314$Dq6.1620@edtnps82, says...


"Derwin" wrote in message
news:6mzYh.5305$Dq6.3498@edtnps82...

I tried to re-cap a tube receiver (amplifier + tuner), and now when I turn
it
on it starts playing music for a few seconds after it warms up, then the
music
fades out and and hum takes over. I don't really know what I'm doing, and
the
wiring inside looks like a mess of spaghetti. I'm pretty sure I replaced
the
caps properly, but I used .068uf WIMA caps to replace .050uf wax/paper
caps,
and I'm wondering if the value difference, added up over 8 caps would make
a
difference?

No.

That's not what I've read. Are you sure you're not thinking of electrolytics?


Other than that, does anyone have any advice based on my
description of the unit's behavior? Any comments whatsoever might be
helpful..

At this point you need to fault find. Does it work OK with tape or other
music input?


Perhaps I should have specified that the unit worked fine before I recapped it.
It had a bit of a squishy sound so I figured it could use a re-capping but I
must've screwed up somehow. But re-capping is pretty straight-forward, and I
think I did it right. So now, what could have gone wrong? Switching inputs is
not going to help me track down the problem at all. C'mon, I may be a
'self-taught' novice electronics tinkerer, but that is downright stupid - I
already said the music plays fine for a few seconds after it warms up then it
fades out, so obviously its not a problem of a flakey input.. sheesh.

Perhaps I should have specified that the unit worked fine before I
recapped it.
It had a bit of a squishy sound so I figured it could use a re-capping
but I
must've screwed up somehow. But re-capping is pretty straight-forward,
and I think I did it right. So now, what could have gone wrong?

It does not work now....

Switching inputs is not going to help me track down the problem at all.
C'mon, I may be a 'self-taught' novice electronics tinkerer, but that
is downright stupid - I already said the music plays fine for a few
seconds after it warms up then it fades out, so obviously its not a
problem of a flakey input.. sheesh.


So troubleshoot it and find the problem. The small difference in capacitor
values you replaced is 99.999999999999999999% likely not to be the problem.

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Are these non-polarized caps? Maybe a polarized one is backwards or
leaking. If you have a VTVM or DVM, check biasing in the amplifier to
see if anything changes while it warms up. Also could be a tube with a
heater-cathode short.

Derwin wrote:

I tried to re-cap a tube receiver (amplifier + tuner), and now when I turn it
on it starts playing music for a few seconds after it warms up, then the music
fades out and and hum takes over. I don't really know what I'm doing, and the
wiring inside looks like a mess of spaghetti. I'm pretty sure I replaced the
caps properly, but I used .068uf WIMA caps to replace .050uf wax/paper caps,
and I'm wondering if the value difference, added up over 8 caps would make a
difference? Other than that, does anyone have any advice based on my
description of the unit's behavior? Any comments whatsoever might be helpful..




--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."

"Follow The Money" ;-P

**THE-RFI-EMI-GUY** wrote:

Are these non-polarized caps? Maybe a polarized one is backwards or
leaking.

Have you ever seen a 0.050uF polarised cap ?????

Puh-leeeze !


Graham

Eeyore ) writes:
**THE-RFI-EMI-GUY** wrote:

Are these non-polarized caps? Maybe a polarized one is backwards or
leaking.

Have you ever seen a 0.050uF polarised cap ?????

But the problem is we don't really know what he did.

He mentions those capacitors because he couldn't get the exact
value, but he said he recapped the receiver. That implies he
changed all the capacitors.

It would have helped if he'd said why he did the recapping. Because
there was an existing problem, and he hoped it would fix it? Because
he wanted to "improve the sound"? Because he figures they are old
enough that they ought to be replaced?

From what he's said, we don't really know if the problem is due
to the recapping, or existed before.

Michael

"Michael Black" wrote in message
...
Eeyore ) writes:
**THE-RFI-EMI-GUY** wrote:

Are these non-polarized caps? Maybe a polarized one is backwards or
leaking.

Have you ever seen a 0.050uF polarised cap ?????

But the problem is we don't really know what he did.

He mentions those capacitors because he couldn't get the exact
value, but he said he recapped the receiver. That implies he
changed all the capacitors.

It would have helped if he'd said why he did the recapping. Because
there was an existing problem, and he hoped it would fix it? Because
he wanted to "improve the sound"? Because he figures they are old
enough that they ought to be replaced?

From what he's said, we don't really know if the problem is due
to the recapping, or existed before.

Michael


He had mentioned he did so because the audio had a "Squishing" sound to it.
So - I suppose we can take that as he was trying to correct for an audio
issue perhaps.

Meat Plow writes:

On Sat, 28 Apr 2007 04:02:09 +0000, Homer J Simpson wrote:


"Derwin" wrote in message
news:6mzYh.5305$Dq6.3498@edtnps82...

I tried to re-cap a tube receiver (amplifier + tuner), and now when I turn
it
on it starts playing music for a few seconds after it warms up, then the
music
fades out and and hum takes over. I don't really know what I'm doing, and
the
wiring inside looks like a mess of spaghetti. I'm pretty sure I replaced
the
caps properly, but I used .068uf WIMA caps to replace .050uf wax/paper
caps,
and I'm wondering if the value difference, added up over 8 caps would make
a
difference?

No.

Other than that, does anyone have any advice based on my
description of the unit's behavior? Any comments whatsoever might be
helpful..

At this point you need to fault find. Does it work OK with tape or other
music input?

I wouldn't delve that far, sounds like a PS/PA problem. The OP is confused
man, he said it looks like spaghetti.

Old equipment wiring does look like spaghetti compared to PCB construction.

DId he replace the electrolytic caps as well?

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Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
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Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

In message zhAYh.5325$Dq6.782@edtnps82, Derwin
writes
It had a bit of a squishy sound so I figured it could use a re-capping but I
must've screwed up somehow. But re-capping is pretty straight-forward, and I
think I did it right. So now, what could have gone wrong?
Hmm, let's think about it for a moment, it worked before you screwed
with it, you screwed around with it, it doesn't work now... Anything
leap out at you? Ten points if you came to the same diagnosis as me...
Switching inputs is
not going to help me track down the problem at all. C'mon, I may be a
'self-taught' novice electronics tinkerer, but that is downright stupid - I
already said the music plays fine for a few seconds after it warms up then it
fades out, so obviously its not a problem of a flakey input.. sheesh.
Flakey downright rude tinkerer IMHO.



--
Clint Sharp

Michael Black wrote:

But the problem is we don't really know what he did.

He mentions those capacitors because he couldn't get the exact
value, but he said he recapped the receiver. That implies he
changed all the capacitors.

It would have helped if he'd said why he did the recapping. Because
there was an existing problem, and he hoped it would fix it? Because
he wanted to "improve the sound"? Because he figures they are old
enough that they ought to be replaced?

From what he's said, we don't really know if the problem is due
to the recapping, or existed before.


It is common practice for people who restore antique radios. Lots of
the paper insulated capacitors are leaky, so the shotgun that problem
before they damage tubes and other parts from improperly biased tubes.
The extra current can even fry an old power transformer. That was why I
recommended the news:rec.antiques.radio+phono newsgroup. Its an
excellent source of parts and information for this old radios. There
are also people there that make reproductions of hard to find parts and
knobs.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Derwin wrote:
I tried to re-cap a tube receiver (amplifier + tuner), and now when I turn it
on it starts playing music for a few seconds after it warms up, then the music
fades out and and hum takes over. I don't really know what I'm doing, and the
wiring inside looks like a mess of spaghetti. I'm pretty sure I replaced the
caps properly, but I used .068uf WIMA caps to replace .050uf wax/paper caps,
and I'm wondering if the value difference, added up over 8 caps would make a
difference? Other than that, does anyone have any advice based on my
description of the unit's behavior? Any comments whatsoever might be helpful..


Obviously what you did caused the problem. Check for cold solder
joints and inadvertent connections via solder flash. If you have
enough information (e.g. a detailed log of what you did, or
before/after photos), go back and recheck your work.

Did it look like spaghetti before you started?

From your description, it sounds like maybe it's drawing more current
now than before, so that the power supply capacitors are no longer
adequate. Does it have a rectifier tube in the power supply? Is it
glowing red? Perhaps you've dramatically changed the bias point in
the output stage by some misconnection.

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

"Michael A. Terrell" ) writes:
Michael Black wrote:

But the problem is we don't really know what he did.

He mentions those capacitors because he couldn't get the exact
value, but he said he recapped the receiver. That implies he
changed all the capacitors.

It would have helped if he'd said why he did the recapping. Because
there was an existing problem, and he hoped it would fix it? Because
he wanted to "improve the sound"? Because he figures they are old
enough that they ought to be replaced?

From what he's said, we don't really know if the problem is due
to the recapping, or existed before.


It is common practice for people who restore antique radios. Lots of
the paper insulated capacitors are leaky, so the shotgun that problem
before they damage tubes and other parts from improperly biased tubes.
The extra current can even fry an old power transformer. That was why I
recommended the news:rec.antiques.radio+phono newsgroup. Its an
excellent source of parts and information for this old radios. There
are also people there that make reproductions of hard to find parts and
knobs.

I'm not arguing against the practice, just pointing out that why
someone does it might help define where the problem lies.

If there was an existing problem, the capacitors just might not
have been the problem.

If there was no problem, but now there is, then it's indicative of some
issue related to the replaced capacitors (though obviously it can always be
some coincidence that something else failed at this moment).

It's not going to be due to those .068uF capacitors because their
value is different, but obviously it could be a bad electrolytic replacement,
or perhaps a reversed electrolytic. It might be a coupling capacitor
that turns out bad. It could be that in the spaghetti the poster overlooked
a capacitor that ends up being the problem.

It's obviously easy to shotgun replace parts when something fails, but
if that doesn't solve the problem, nothing's been done to figure out
where the problem lies. As it now stands, the capacitors have been
changed and there is still a problem.

Michael

Hi!

Perhaps I should have specified that the unit worked fine before
I recapped it. It had a bit of a squishy sound so I figured it could
use a re-capping but I must've screwed up somehow.

Perhaps you have a new capacitor that is bad? It is unlikely but *does*
happen. A check would be worthwhile and won't take too long.

So now, what could have gone wrong?

There could be a bad cap, or another component that failed. You will have to
do some testing of the unit.

Switching inputs is not going to help me track down the problem at all.

Yes it can. If you still don't agree, stop and think about the the
construction of most audio amplifying equipment. Many power
amplifier/receiver units have multiple inputs that may be selected. All of
them lead to the same place, but before they are merged, each one is a
separate circuit...and a fault could develop in the circuitry that is unique
to each input. If you haven't tried this idea, hook up your audio source to
another compatible input. For example, if you're using a tuner as an audio
source, you could hook it to any of the tuner connector, tape connector or
even the AUX connector. On most equipment they all use similar signal levels
and characteristics.

Please take the suggestions you receive seriously. No one here can see your
workbench or know some of the things you know about the equipment you're
working on. For that reason, we *have* to cover the basics in an effort to
get on the same page that you are on.

William

Derwin wrote:
I tried to re-cap a tube receiver (amplifier + tuner), and now when I turn it
on it starts playing music for a few seconds after it warms up, then the music
fades out and and hum takes over. I don't really know what I'm doing, and the
wiring inside looks like a mess of spaghetti. I'm pretty sure I replaced the
caps properly, but I used .068uf WIMA caps to replace .050uf wax/paper caps,
and I'm wondering if the value difference, added up over 8 caps would make a
difference? Other than that, does anyone have any advice based on my
description of the unit's behavior? Any comments whatsoever might be helpful..

Sounds like you got an electrolytic cap in backward. They are polarity
sensitive.

Bill

"Derwin" wrote in message
news:6mzYh.5305$Dq6.3498@edtnps82...
I tried to re-cap a tube receiver (amplifier + tuner), and now when I turn
it
on it starts playing music for a few seconds after it warms up, then the
music
fades out and and hum takes over. I don't really know what I'm doing, and
the
wiring inside looks like a mess of spaghetti. I'm pretty sure I replaced
the
caps properly, but I used .068uf WIMA caps to replace .050uf wax/paper
caps,
and I'm wondering if the value difference, added up over 8 caps would make
a
difference? Other than that, does anyone have any advice based on my
description of the unit's behavior? Any comments whatsoever might be
helpful..

Maybe a tube has gone west ... internal leakage caused by mechanical
disturbance when working on it? Tubes get hot and sometimes cathode leakage
follows a brief warm-up period.

Also, you did not mention the voltage ratings of the capacitors.

Often, hum is caused by the power supply filter caps but your symptoms don't
quite fit that.

Derwin wrote:
In article 5HzYh.5314$Dq6.1620@edtnps82, says...


"Derwin" wrote in message
news:6mzYh.5305$Dq6.3498@edtnps82...


I tried to re-cap a tube receiver (amplifier + tuner), and now when I turn
it
on it starts playing music for a few seconds after it warms up, then the
music
fades out and and hum takes over. I don't really know what I'm doing, and
the
wiring inside looks like a mess of spaghetti. I'm pretty sure I replaced
the
caps properly, but I used .068uf WIMA caps to replace .050uf wax/paper
caps,
and I'm wondering if the value difference, added up over 8 caps would make
a
difference?

No.


That's not what I've read. Are you sure you're not thinking of electrolytics?


Other than that, does anyone have any advice based on my
description of the unit's behavior? Any comments whatsoever might be
helpful..

At this point you need to fault find. Does it work OK with tape or other
music input?



Perhaps I should have specified that the unit worked fine before I recapped it.
It had a bit of a squishy sound so I figured it could use a re-capping but I
must've screwed up somehow. But re-capping is pretty straight-forward, and I
think I did it right. So now, what could have gone wrong? Switching inputs is
not going to help me track down the problem at all. C'mon, I may be a
'self-taught' novice electronics tinkerer, but that is downright stupid - I
already said the music plays fine for a few seconds after it warms up then it
fades out, so obviously its not a problem of a flakey input.. sheesh.


My guess is that it is a heater-cathode short in one of the audio tubes.
My reasoning is that when a tube is cold the elements are not shorting
but after some thermal expansion they may short out. Why it is doing it
now but not before could be from turning the chassis upside/down and
having a piece of crap in side the tube in question move to a sensitive
area.

Electrolytics if leaky will hum first and then play which is the
opposite of what is happening.

Personally, I would change ALL the caps at least in the ausio section
including the power supply electrolytics.

Hope this may shed some light for you.

Jim

Jim Poore wrote:
Derwin wrote:

In article 5HzYh.5314$Dq6.1620@edtnps82, says...


"Derwin" wrote in message
news:6mzYh.5305$Dq6.3498@edtnps82...


I tried to re-cap a tube receiver (amplifier + tuner), and now when
I turn it
on it starts playing music for a few seconds after it warms up, then
the music
fades out and and hum takes over. I don't really know what I'm
doing, and the
wiring inside looks like a mess of spaghetti. I'm pretty sure I
replaced the
caps properly, but I used .068uf WIMA caps to replace .050uf
wax/paper caps,
and I'm wondering if the value difference, added up over 8 caps
would make a
difference?


No.



That's not what I've read. Are you sure you're not thinking of
electrolytics?


Other than that, does anyone have any advice based on my
description of the unit's behavior? Any comments whatsoever might
be helpful..


At this point you need to fault find. Does it work OK with tape or
other music input?



Perhaps I should have specified that the unit worked fine before I
recapped it. It had a bit of a squishy sound so I figured it could
use a re-capping but I must've screwed up somehow. But re-capping is
pretty straight-forward, and I think I did it right. So now, what
could have gone wrong? Switching inputs is not going to help me track
down the problem at all. C'mon, I may be a 'self-taught' novice
electronics tinkerer, but that is downright stupid - I already said
the music plays fine for a few seconds after it warms up then it fades
out, so obviously its not a problem of a flakey input.. sheesh.


My guess is that it is a heater-cathode short in one of the audio tubes.
My reasoning is that when a tube is cold the elements are not shorting
but after some thermal expansion they may short out. Why it is doing it
now but not before could be from turning the chassis upside/down and
having a piece of crap in side the tube in question move to a sensitive
area.

Electrolytics if leaky will hum first and then play which is the
opposite of what is happening.

Personally, I would change ALL the caps at least in the ausio section
including the power supply electrolytics.

Hope this may shed some light for you.

Jim
I forgot to mention one thing. What is the voltage rating of the caps
you changed? Is it the same of higher than the ones you replaced? If
the voltage rating is too low that caps might breakdown under voltage.

In tube equipment a good rule of thumb is just go with a 600V rating on
the capacitors. Some amplifiers and I am goin on memory here with
6CA7's may have even higher voltages to deal with.

Jim

(Derwin) wrote in news:4bAYh.5322$Dq6.2769@edtnps82:

In article ,
l says...

On Sat, 28 Apr 2007 04:02:09 +0000, Homer J Simpson wrote:


"Derwin" wrote in message
news:6mzYh.5305$Dq6.3498@edtnps82...

I tried to re-cap a tube receiver (amplifier + tuner), and now when I
turn it
on it starts playing music for a few seconds after it warms up, then
the music
fades out and and hum takes over. I don't really know what I'm
doing, and the
wiring inside looks like a mess of spaghetti. I'm pretty sure I
replaced the
caps properly, but I used .068uf WIMA caps to replace .050uf
wax/paper caps,
and I'm wondering if the value difference, added up over 8 caps would
make a
difference?


First, you need to 'divide and conquer'. Divide the set in half and
determine which half holds the problem. Is it the receiver section or the
amplifier section?

Signal injection and signal tracing should let you determine which half the
problem is in.

If it is in the receiver, you will need to determine whether it is in the
front end (tuner), the oscillator, or the IF, or the detector.

If it is the amplifier you should again be able to narrow down the problem
to what section of the audio amplifier.

It is possible that you have an open grid leak resistor.
With leaky bypass capacitorys, one of them might have been 'doing double
duty'. When you replaced the caps, you may have thrown away a significant
portion of the grid leak.

Check for a grid that is going highly negative and cutting off the tube
(plate voltage going high).

Check for open resistors.

It is also possible that one of the new capacitors is defective.

Look in a tube manual and look at the curves for the tubes used in the
amp.. In an audio amplifier, you would expect class A operation, with the
tube biased into the middle of a linear portion of the curve unless you
have push/pull amplifier, in which case a pair of tubes would work against
each other in class AB or B.

Hope this helps.
.....



--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

Michael Black wrote:

It's obviously easy to shotgun replace parts when something fails, but
if that doesn't solve the problem, nothing's been done to figure out
where the problem lies. As it now stands, the capacitors have been
changed and there is still a problem.


Some restorers claim that over 80% of the are capacitors are leaky.
They replace them all, because the others are going to fail, and its
easier to do the repair ONCE instead of pulling the chassis every year
or two to check the few that were good.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

In article ,
l says...

Surely you jest. You mentioned spaghetti first so by your logic, you made
the first racist remark.


Ah but you decided that because I mentioned spaghetti that you were going to
continue to insult me. Go away old man, you're senile.

In article 39,
says...

(Derwin) wrote in news:4bAYh.5322$Dq6.2769@edtnps82:

In article ,
l says...

On Sat, 28 Apr 2007 04:02:09 +0000, Homer J Simpson wrote:


"Derwin" wrote in message
news:6mzYh.5305$Dq6.3498@edtnps82...

I tried to re-cap a tube receiver (amplifier + tuner), and now when I
turn it
on it starts playing music for a few seconds after it warms up, then
the music
fades out and and hum takes over. I don't really know what I'm
doing, and the
wiring inside looks like a mess of spaghetti. I'm pretty sure I
replaced the
caps properly, but I used .068uf WIMA caps to replace .050uf
wax/paper caps,
and I'm wondering if the value difference, added up over 8 caps would
make a
difference?


First, you need to 'divide and conquer'. Divide the set in half and
determine which half holds the problem. Is it the receiver section or the
amplifier section?

Signal injection and signal tracing should let you determine which half the
problem is in.

If it is in the receiver, you will need to determine whether it is in the
front end (tuner), the oscillator, or the IF, or the detector.

If it is the amplifier you should again be able to narrow down the problem
to what section of the audio amplifier.

It is possible that you have an open grid leak resistor.
With leaky bypass capacitorys, one of them might have been 'doing double
duty'. When you replaced the caps, you may have thrown away a significant
portion of the grid leak.

Check for a grid that is going highly negative and cutting off the tube
(plate voltage going high).

Check for open resistors.

It is also possible that one of the new capacitors is defective.

Look in a tube manual and look at the curves for the tubes used in the
amp.. In an audio amplifier, you would expect class A operation, with the
tube biased into the middle of a linear portion of the curve unless you
have push/pull amplifier, in which case a pair of tubes would work against
each other in class AB or B.

Hope this helps.


Yes, the parts about the grid resistor and reminding me that one of the new
caps might be faulty was helpful. Thanks.

In article , says...


I wouldn't delve that far, sounds like a PS/PA problem. The OP is confused
man, he said it looks like spaghetti.

Old equipment wiring does look like spaghetti compared to PCB construction.


Yes it does, but apparently that's offensive to Meathead.


DId he replace the electrolytic caps as well?



Yes, I replaced the wax paper ones first, then the electrolytics. I should
have turned it on after doing the wax paper ones because that would've narrowed
down the problem considerably, but I didn't. It all looked pretty
straightforward and I expected it to work.. but considering the age of some of
the other components and wires in there, I should've known better.

In article ,
l says...

On Sat, 28 Apr 2007 04:43:11 +0000, Derwin wrote:

In article 5HzYh.5314$Dq6.1620@edtnps82, says...


"Derwin" wrote in message
news:6mzYh.5305$Dq6.3498@edtnps82...

I tried to re-cap a tube receiver (amplifier + tuner), and now when I turn
it
on it starts playing music for a few seconds after it warms up, then the
music
fades out and and hum takes over. I don't really know what I'm doing, and
the
wiring inside looks like a mess of spaghetti. I'm pretty sure I replaced
the
caps properly, but I used .068uf WIMA caps to replace .050uf wax/paper
caps,
and I'm wondering if the value difference, added up over 8 caps would make
a
difference?

No.

That's not what I've read. Are you sure you're not thinking of
electrolytics?


Other than that, does anyone have any advice based on my
description of the unit's behavior? Any comments whatsoever might be
helpful..

At this point you need to fault find. Does it work OK with tape or other
music input?


Perhaps I should have specified that the unit worked fine before I recapped
it.
It had a bit of a squishy sound so I figured it could use a re-capping but
I
must've screwed up somehow. But re-capping is pretty straight-forward, and
I
think I did it right. So now, what could have gone wrong? Switching inputs
is
not going to help me track down the problem at all. C'mon, I may be a
'self-taught' novice electronics tinkerer, but that is downright stupid - I
already said the music plays fine for a few seconds after it warms up then
it
fades out, so obviously its not a problem of a flakey input.. sheesh.

How the hell is anyone on the other end of the internet going to know what
the hell you "screwed up somehow"? That's absolutely absurd. Toss the
****er in the trash you idiot.


Only a moron like you would do something like that. There's always at least
one or two people on each newsgroup with no life who spend all day every day
saying stupid things to anyone who happens to post looking for information.
I bet you even think you're unique. I've been swatting usenet flies like you
for the past 15 years, ever since the internet went commercial and twits like
you found out you couldn't be kicked off usenet so you set up camp here in
droves...

Retards and the socially inept should be smiling and happy, not scowling
meanies. Why don't you try riding a public bus while farting and giggling?
Seems to cheer up most of the retards in my neighborhood.

In article 40NYh.22211$n_.17913@attbi_s21,
says...


Please take the suggestions you receive seriously. No one here can see your
workbench or know some of the things you know about the equipment you're
working on.

They should at least know that an ancient tube receiver is not going to have
more than one input. It's rare for a tube receiver to even have a single AUX
input, only high-end models had an input. I was hoping to hear from people
with experience with tube receivers, and people who suggest testing a matrix of
inputs clearly do not.

In article ,
says...


Flakey downright rude tinkerer IMHO.

More like tinkerer who doesn't suffer fools gladly. Considering I've been
cordial and thankful to those who have responded cordially and helpfully, why
should I patronize the jerks? As long as non-jerks respond, which they have,
anything posted by the jerk-squad is superfulous, and can be either ignored, or
ridiculed. Either way they're useless responses so it doesn't matter how or
if I reply to them. I've been using usenet for long enough to know that any
time I post to any group looking for information, half of the responses are
likely going to be from socially-deranged usenet-lifers. Socially-deranged
usenet-lifers are always in denial and don't realize that they are
socially-deranged usenet-lifers. Some of the time I think they even believe
they are offering helpful advice, because if they don't pepper their initial
reponses with insults they expect immense gratitude, even if what they said was
inapplicable or irrelevent.

In article , says...


I forgot to mention one thing. What is the voltage rating of the caps
you changed? Is it the same of higher than the ones you replaced?

Of course. And from now on, if I don't respond to a question that assumes I am
dumber than I am, assume the answer is that I wasn't that dumb, Ok? For
example, if the next thing someone asks is if I plugged the power cord into a
power socket in the wall, assume that I did when I don't bother responding.

If I didn't know that I had to replace caps with an equal or higher voltage
rating, I wouldn't have tried re-capping the unit in the first place. In fact,
I would think that anyone who didn't know that wouldn't know the difference
between electrolytic caps and wax paper ones anyway.

In article , says...



My guess is that it is a heater-cathode short in one of the audio tubes.
My reasoning is that when a tube is cold the elements are not shorting
but after some thermal expansion they may short out. Why it is doing it
now but not before could be from turning the chassis upside/down and
having a piece of crap in side the tube in question move to a sensitive
area.

Electrolytics if leaky will hum first and then play which is the
opposite of what is happening.

Personally, I would change ALL the caps at least in the ausio section
including the power supply electrolytics.

Hope this may shed some light for you.

The first two paragraphs were helpful, but I certainly don't understand why you
would recommend replacing caps I just replaced. Checking to see if one of the
new caps I installed is bad is one thing, but replacing all the new caps I just
installed with another set of new caps sounds like an excersize in throwing
money down the toilet and nothing else.

In article , says...

Are these non-polarized caps? Maybe a polarized one is backwards or
leaking.

non-electrolytics are not polarized, and doncha think I would've double,
triple, and quadruple-checked the orientation of the electrolytics I just
installed BEFORE posting here, knowing that doing so would be opening myself up
to A) redundant or irrelevent responses and B) abuse from the usenet-lifers who
consider any post for advice to be troll-bait?

In article , says...

Eeyore ) writes:
**THE-RFI-EMI-GUY** wrote:

Are these non-polarized caps? Maybe a polarized one is backwards or
leaking.

Have you ever seen a 0.050uF polarised cap ?????

But the problem is we don't really know what he did.

He mentions those capacitors because he couldn't get the exact
value, but he said he recapped the receiver.

No Michael, I said that I replacede .050uF wax paper caps with .068uf WIMA
caps. Eeyore is right, it was a stupid reply.


It would have helped if he'd said why he did the recapping. Because
there was an existing problem, and he hoped it would fix it? Because
he wanted to "improve the sound"? Because he figures they are old
enough that they ought to be replaced?

From what he's said, we don't really know if the problem is due
to the recapping, or existed before.

Perhaps you should've read my next post in the thread which answered those
questions, before wasting your time with your irrelevnet post? My post with
those answers was posted long before you decided to post pretending I hadn't
already answered those questions.

In article , says...

Derwin wrote:
I tried to re-cap a tube receiver (amplifier + tuner), and now when I turn
it
on it starts playing music for a few seconds after it warms up, then the
music
fades out and and hum takes over. I don't really know what I'm doing, and
the
wiring inside looks like a mess of spaghetti. I'm pretty sure I replaced
the
caps properly, but I used .068uf WIMA caps to replace .050uf wax/paper caps,
and I'm wondering if the value difference, added up over 8 caps would make a
difference? Other than that, does anyone have any advice based on my
description of the unit's behavior? Any comments whatsoever might be
helpful..


Obviously what you did caused the problem. Check for cold solder
joints and inadvertent connections via solder flash. If you have
enough information (e.g. a detailed log of what you did, or
before/after photos), go back and recheck your work.

Did it look like spaghetti before you started?


YES. Why are you even replying if you obviously have never looked inside an
old tube amp?


From your description, it sounds like maybe it's drawing more current
now than before, so that the power supply capacitors are no longer
adequate. Does it have a rectifier tube in the power supply?

probably

Is it
glowing red?

they're all glowing and I tested every tube a few months ago and they were all
fine. I no longer have a tube-tester to check again, however.

Perhaps you've dramatically changed the bias point in
the output stage by some misconnection.


All the caps I replaced are connected exactly where they were before I replaced
them. What I'm thinking is that the guy who sold it to me, after having
'restored' it from non-working condition wired it up in some jeri-rigged
fashion to get it to look like it was working enough to be able to sell it to
me. Probably one of the caps was bad and compensating for a bad resistor as
someone else mentioned. However, the wiring he added did not contribute to the
'spaghetti' much. Anyone who has ever looked inside any old electronics from
before the days of circuit-boards will know what 'spaghetti' wiring looks like.
Those who havent, try this: Look at a circuitboard populated with a bunch of
components. Look at the traces the circuit makes on the back of the board. Now
imagine each one of those traces being replaced with a wire. Now perhaps you
will be able to envision the 'spaghetti' wiring that a circuit not build on a
PCB will look like.. Anyway now I'm pretty much screwed. I don't own an
oscilliscope so I will probably just sell off the tubes and toss the chassis.
I prefer the sound of solid-state these days anyway, my interest in tube gear
was a folly that only lasted a couple years.

In article ,
says...


"Derwin" wrote in message
news:6mzYh.5305$Dq6.3498@edtnps82...
I tried to re-cap a tube receiver (amplifier + tuner), and now when I turn
it
on it starts playing music for a few seconds after it warms up, then the
music
fades out and and hum takes over. I don't really know what I'm doing, and
the
wiring inside looks like a mess of spaghetti. I'm pretty sure I replaced
the
caps properly, but I used .068uf WIMA caps to replace .050uf wax/paper
caps,
and I'm wondering if the value difference, added up over 8 caps would make
a
difference? Other than that, does anyone have any advice based on my
description of the unit's behavior? Any comments whatsoever might be
helpful..

Maybe a tube has gone west ... internal leakage caused by mechanical
disturbance when working on it? Tubes get hot and sometimes cathode leakage
follows a brief warm-up period.

Also, you did not mention the voltage ratings of the capacitors.

That's because I already knew that I had replaced the caps with caps of equal
or higher voltage specs. I could've written 20 pages describing every detail,
but I omit the details that don't matter in order to emphasize the details that
do matter. But I do understand that that particular detail matters enough that
I probably should have reassured readers that I was already ontop of it.


Often, hum is caused by the power supply filter caps but your symptoms don't
quite fit that.



Thanks for being one of the few responders who was able to consider the
symptoms and extrapolate some possibilities from the symptoms.

Hi!

They should at least know that an ancient tube receiver is not going
to have more than one input.

That's simply not true. Please look at the following:
http://greyghost.dyndns.org/knight/
and note the source selection knob on the far right of the amp.

I can select from tuner, tape, turntable, and auxiliary inputs on that
receiver. It is very clearly tube powered (4xEL84). This is a 1959 era
receiver. At that time, many people had a desire to hear not only radio
programming, but also selections from their collection of record albums. If
you purchased a separate amp.

Yes, I see you saying something like "that's not the ancient I had in mind"
and I do suppose you have to draw the line somewhere when looking at various
generations of technology. 1959 wasn't exactly yesterday, however. :-) Even
many older systems have at least a switch between tuner and phono sources.

I don't know that I believe it when you say that it is rare for a tube
receiver to have multiple inputs. I don't doubt but what yours could be
different--however, we still have no model number or even a brand name to go
by.

As I said before, please *don't* make it difficult. We're all here to help.
Put quite bluntly, nobody here is in any way required to help you. I
sincerely suggest you consider this when visiting any public forum and
asking for assistance. This desire to help tends to get a bit "squelched" in
the face of rude behavior.

And I still think testing your newly installed capacitors is a good
idea...should you get the amp fixed, I would like to know how it played out,
if you are willing to say.

William

In article 6QWYh.84494$_c5.11297@attbi_s22,
says...


I can select from tuner, tape, turntable, and auxiliary inputs on that
receiver.

the tuner isnt an input, and besides the pre-amp on the turntable input, the
circuit is the same between the tape and aux inputs, it's just switched.
That's what the knob you're selecting with does. What, you think they build
seperate pre-amps for aux and tape inputs?

On 4/29/07 12:01 AM, in article DpXYh.7901$Dq6.560@edtnps82, "Derwin"
wrote:

In article 6QWYh.84494$_c5.11297@attbi_s22,
says...


I can select from tuner, tape, turntable, and auxiliary inputs on that
receiver.

the tuner isnt an input, and besides the pre-amp on the turntable input, the
circuit is the same between the tape and aux inputs, it's just switched.
That's what the knob you're selecting with does. What, you think they build
seperate pre-amps for aux and tape inputs?


Of course the tuner is an input.

Yes, they are often different; each may require unique equalization.

You really are being petulant, Throw it away and get goldfish for a hobby.

(Derwin) wrote in
news:6mzYh.5305$Dq6.3498@edtnps82:

I tried to re-cap a tube receiver (amplifier + tuner), and now when I
turn it on it starts playing music for a few seconds after it warms
up, then the music fades out and and hum takes over. I don't really
know what I'm doing, and the wiring inside looks like a mess of
spaghetti. I'm pretty sure I replaced the caps properly, but I used
.068uf WIMA caps to replace .050uf wax/paper caps, and I'm wondering
if the value difference, added up over 8 caps would make a difference?
Other than that, does anyone have any advice based on my description
of the unit's behavior? Any comments whatsoever might be helpful..



Do you have a tube manual, look up G1 of the preamp and power output
tubes. Check the dc voltage when it is not working they should not be a
positive voltage on them if so check the new capacitor connected to that
tube. Extremely high negative voltage check the grid resistor.

Of course I assume you have a high imput impeadance voltmeter there.

I would like the brand and model # if you wouldn't mind.

R!

Hi!

the tuner isnt an input

Suit yourself. You're more than welcome to believe whatever you like, even
when the tuner is clearly external to the amp.

:-)

What, you think they build
seperate pre-amps for aux and tape inputs?

That very much depends upon the design of the amplifier.

I've tried to offer some help and correction to some beliefs that aren't
universally correct. All the while I've been fairly polite about the whole
thing. I guess there are some people who just can't/won't/don't want to be
told or helped. You seem to be one of those types. So, I won't reply any
further. Good luck with your amplifier, though. I do hope you get it fixed
and working well.

William

Derwin wrote:
In article ,
says...


Flakey downright rude tinkerer IMHO.


More like tinkerer who doesn't suffer fools gladly. Considering I've been
cordial and thankful to those who have responded cordially and helpfully, why
should I patronize the jerks? As long as non-jerks respond, which they have,
anything posted by the jerk-squad is superfulous, and can be either ignored, or
ridiculed. Either way they're useless responses so it doesn't matter how or
if I reply to them. I've been using usenet for long enough to know that any
time I post to any group looking for information, half of the responses are
likely going to be from socially-deranged usenet-lifers. Socially-deranged
usenet-lifers are always in denial and don't realize that they are
socially-deranged usenet-lifers. Some of the time I think they even believe
they are offering helpful advice, because if they don't pepper their initial
reponses with insults they expect immense gratitude, even if what they said was
inapplicable or irrelevent.


I agree. I am a professional electronics tech for over 40 years and
nowhere in this newsgroup does it say its for professionals only. I
applaud those people who want to challenge themselves and tackle
something they haven't done before. I can say I have made many mistakes,
some rookie mistakes and some that I knew better but made them anyway.
My worst was resting my left arm on a metal TV cabinet with a mirror as
I was making an adjustment. I caught a stand-up resistor in the power
supply right off the rectifier tube with my right arm and almost ended
my life. Pretty dumb. But I am sure we have all made some mistakes like
solder bridges or cold solder, wrong values, etc.

Now...the absolute best advice I can give is that in a new venture that
one has not undertaken before is to ask FIRST in this newsgroup. I
myself would be more than happy to point someone in the right direction
before they start. Remember there are no stupid questions, only stupid
answers.

Jim