** Had an early 1960s guitar amp in this week, a "Maestro Viscount" made by
Gibson, aka the GA-16T. All the valves were new, JJ types: 2 x ECC803, 2x
6V6S and a 5Y3.

The accompanying note contained no fault report and asked only for two
modest modifications:

1. Replace and rewire speaker wire with heavier wire.

2. Rewire to shorten power feed cable from tranny.

The speaker wires were soldered at both ends and just long enough to let the
chassis rest on a bench. The AC cable referred to was internal and went from
the chassis to a 230V to 115 V step-down fitted in the factory 50 years ago.
The two wire cable had been wound neatly like a rope and rested on the
bottom of the case next to the step-down.

The 240V lead was modern, 3 core and there was a wire linking the frame of
the step-down to the chassis.

I connected the amp to my Variac and gradually powered it up to about
00V - just as I expected it let out an almighty hum, mostly 50Hz, through
the speaker. The hum mostly disappeared if the volume pot was turned down.

Of course bad electros were the cause of the trouble, but the situation was
not so simple since as someone had been there before me, decades ago and
substituted two pigtail electros for ones inside a triple electro that was
mounted off the chassis on a clamp.

It soon became clear that the third electro in the triple had now expired -
but that should cause only 100Hz hum, not 50Hz.

Then came the *shocker*, one of the pigtail electros was grounded to the AC
heater supply instead of the chassis - this imposed 3.15 volts AC at 50Hz on
a DC rail ( the screen supply) that should have had only a trace of 100Hz
ripple.

Removing the dead triple electro, adding a new pigtail one and rewiring soon
put things straight leaving only a minor amount of 100Hz buzz at full
volume.

There was one pigtail electro hanging onto the 5Y3 socket, grounded to a lug
on the frame. Soon as I shifted the ground point to the common chassis
ground, even that hum vanished.

With the amp now working nicely, I modified the speaker and internal AC
leads as requested in the customer's note.

Apparently the customer believed the AC lead tied like a rope was causing
the hum.

Oh dear..........


.... Phil

Phil Allison wrote:

** Had an early 1960s guitar amp in this week, a "Maestro Viscount" made by
Gibson, aka the GA-16T. All the valves were new, JJ types: 2 x ECC803, 2x
6V6S and a 5Y3.

The accompanying note contained no fault report and asked only for two
modest modifications:

1. Replace and rewire speaker wire with heavier wire.

2. Rewire to shorten power feed cable from tranny.

The speaker wires were soldered at both ends and just long enough to let the
chassis rest on a bench. The AC cable referred to was internal and went from
the chassis to a 230V to 115 V step-down fitted in the factory 50 years ago.
The two wire cable had been wound neatly like a rope and rested on the
bottom of the case next to the step-down.

The 240V lead was modern, 3 core and there was a wire linking the frame of
the step-down to the chassis.

I connected the amp to my Variac and gradually powered it up to about
00V - just as I expected it let out an almighty hum, mostly 50Hz, through
the speaker. The hum mostly disappeared if the volume pot was turned down.

Of course bad electros were the cause of the trouble, but the situation was
not so simple since as someone had been there before me, decades ago and
substituted two pigtail electros for ones inside a triple electro that was
mounted off the chassis on a clamp.

It soon became clear that the third electro in the triple had now expired -
but that should cause only 100Hz hum, not 50Hz.

Then came the *shocker*, one of the pigtail electros was grounded to the AC
heater supply instead of the chassis - this imposed 3.15 volts AC at 50Hz on
a DC rail ( the screen supply) that should have had only a trace of 100Hz
ripple.

Removing the dead triple electro, adding a new pigtail one and rewiring soon
put things straight leaving only a minor amount of 100Hz buzz at full
volume.

There was one pigtail electro hanging onto the 5Y3 socket, grounded to a lug
on the frame. Soon as I shifted the ground point to the common chassis
ground, even that hum vanished.

With the amp now working nicely, I modified the speaker and internal AC
leads as requested in the customer's note.

Apparently the customer believed the AC lead tied like a rope was causing
the hum.

Oh dear..........

It was still an honest repair, so everyone wins. I'm sure it took less
time to swap the wires than to explain it was something else.

I worked at a shop once and we used random 1/2 watt carbon resitors
soldered to a couple feet of wire as an antenna for testing stuff- just
jam it into a F connector and you're done. The resistor body was at most a
handle, and not even in series with the whip.

sure enough, people were fascinated by these as the benches were visible
to customers over the counter, and wanted to buy them. No amount of
explanation or laughter would discourage them.

So yes, if they were persistent, we'd make them their own for a couple
bucks.

"Cydrome Leader"
Phil Allison


** Had an early 1960s guitar amp in this week, a "Maestro Viscount" made
by
Gibson, aka the GA-16T. All the valves were new, JJ types: 2 x ECC803,
2x
6V6S and a 5Y3.

The accompanying note contained no fault report and asked only for two
modest modifications:

1. Replace and rewire speaker wire with heavier wire.

2. Rewire to shorten power feed cable from tranny.

The speaker wires were soldered at both ends and just long enough to let
the
chassis rest on a bench. The AC cable referred to was internal and went
from
the chassis to a 230V to 115 V step-down fitted in the factory 50 years
ago.
The two wire cable had been wound neatly like a rope and rested on the
bottom of the case next to the step-down.

The 240V lead was modern, 3 core and there was a wire linking the frame
of
the step-down to the chassis.

I connected the amp to my Variac and gradually powered it up to about
00V - just as I expected it let out an almighty hum, mostly 50Hz,
through
the speaker. The hum mostly disappeared if the volume pot was turned
down.

Of course bad electros were the cause of the trouble, but the situation
was
not so simple since as someone had been there before me, decades ago and
substituted two pigtail electros for ones inside a triple electro that
was
mounted off the chassis on a clamp.

It soon became clear that the third electro in the triple had now
expired -
but that should cause only 100Hz hum, not 50Hz.

Then came the *shocker*, one of the pigtail electros was grounded to the
AC
heater supply instead of the chassis - this imposed 3.15 volts AC at 50Hz
on
a DC rail ( the screen supply) that should have had only a trace of 100Hz
ripple.

Removing the dead triple electro, adding a new pigtail one and rewiring
soon
put things straight leaving only a minor amount of 100Hz buzz at full
volume.

There was one pigtail electro hanging onto the 5Y3 socket, grounded to a
lug
on the frame. Soon as I shifted the ground point to the common chassis
ground, even that hum vanished.

With the amp now working nicely, I modified the speaker and internal AC
leads as requested in the customer's note.

Apparently the customer believed the AC lead tied like a rope was causing
the hum.

Oh dear..........

It was still an honest repair, so everyone wins. I'm sure it took less
time to swap the wires than to explain it was something else.


** Sure - I did what the note asked to avoid an argument and since doing it
caused no harm, why not ?

The main point of my post was the grossly incompetent previous repair that I
found.

Can you figure out how the amp ever worked OK afterwards ?



.... Phil

"Phil Allison" wrote in message
...

"Cydrome Leader"
Phil Allison


** Had an early 1960s guitar amp in this week, a "Maestro Viscount" made
by
Gibson, aka the GA-16T. All the valves were new, JJ types: 2 x ECC803,
2x
6V6S and a 5Y3.

The accompanying note contained no fault report and asked only for two
modest modifications:

1. Replace and rewire speaker wire with heavier wire.

2. Rewire to shorten power feed cable from tranny.

The speaker wires were soldered at both ends and just long enough to let
the
chassis rest on a bench. The AC cable referred to was internal and went
from
the chassis to a 230V to 115 V step-down fitted in the factory 50 years
ago.
The two wire cable had been wound neatly like a rope and rested on the
bottom of the case next to the step-down.

The 240V lead was modern, 3 core and there was a wire linking the frame
of
the step-down to the chassis.

I connected the amp to my Variac and gradually powered it up to about
00V - just as I expected it let out an almighty hum, mostly 50Hz,
through
the speaker. The hum mostly disappeared if the volume pot was turned
down.

Of course bad electros were the cause of the trouble, but the situation
was
not so simple since as someone had been there before me, decades ago and
substituted two pigtail electros for ones inside a triple electro that
was
mounted off the chassis on a clamp.

It soon became clear that the third electro in the triple had now
expired -
but that should cause only 100Hz hum, not 50Hz.

Then came the *shocker*, one of the pigtail electros was grounded to the
AC
heater supply instead of the chassis - this imposed 3.15 volts AC at
50Hz on
a DC rail ( the screen supply) that should have had only a trace of
100Hz
ripple.

Removing the dead triple electro, adding a new pigtail one and rewiring
soon
put things straight leaving only a minor amount of 100Hz buzz at full
volume.

There was one pigtail electro hanging onto the 5Y3 socket, grounded to a
lug
on the frame. Soon as I shifted the ground point to the common chassis
ground, even that hum vanished.

With the amp now working nicely, I modified the speaker and internal AC
leads as requested in the customer's note.

Apparently the customer believed the AC lead tied like a rope was
causing
the hum.

Oh dear..........

It was still an honest repair, so everyone wins. I'm sure it took less
time to swap the wires than to explain it was something else.


** Sure - I did what the note asked to avoid an argument and since doing
it caused no harm, why not ?

The main point of my post was the grossly incompetent previous repair that
I found.

Can you figure out how the amp ever worked OK afterwards ?



Sure. They got tired of the loud hum and turned it off before any damage
occured. Then someone competent repaired it.

"tm"
"Phil Allison"
"Cydrome Leader"
Phil Allison


** Had an early 1960s guitar amp in this week, a "Maestro Viscount"
made by
Gibson, aka the GA-16T. All the valves were new, JJ types: 2 x ECC803,
2x
6V6S and a 5Y3.

The accompanying note contained no fault report and asked only for two
modest modifications:

1. Replace and rewire speaker wire with heavier wire.

2. Rewire to shorten power feed cable from tranny.

The speaker wires were soldered at both ends and just long enough to
let the
chassis rest on a bench. The AC cable referred to was internal and went
from
the chassis to a 230V to 115 V step-down fitted in the factory 50 years
ago.
The two wire cable had been wound neatly like a rope and rested on the
bottom of the case next to the step-down.

The 240V lead was modern, 3 core and there was a wire linking the frame
of
the step-down to the chassis.

I connected the amp to my Variac and gradually powered it up to about
00V - just as I expected it let out an almighty hum, mostly 50Hz,
through
the speaker. The hum mostly disappeared if the volume pot was turned
down.

Of course bad electros were the cause of the trouble, but the situation
was
not so simple since as someone had been there before me, decades ago
and
substituted two pigtail electros for ones inside a triple electro that
was
mounted off the chassis on a clamp.

It soon became clear that the third electro in the triple had now
expired -
but that should cause only 100Hz hum, not 50Hz.

Then came the *shocker*, one of the pigtail electros was grounded to
the AC
heater supply instead of the chassis - this imposed 3.15 volts AC at
50Hz on
a DC rail ( the screen supply) that should have had only a trace of
100Hz
ripple.

Removing the dead triple electro, adding a new pigtail one and rewiring
soon
put things straight leaving only a minor amount of 100Hz buzz at full
volume.

There was one pigtail electro hanging onto the 5Y3 socket, grounded to
a lug
on the frame. Soon as I shifted the ground point to the common chassis
ground, even that hum vanished.

With the amp now working nicely, I modified the speaker and internal AC
leads as requested in the customer's note.

Apparently the customer believed the AC lead tied like a rope was
causing
the hum.

Oh dear..........

It was still an honest repair, so everyone wins. I'm sure it took less
time to swap the wires than to explain it was something else.


** Sure - I did what the note asked to avoid an argument and since doing
it caused no harm, why not ?

The main point of my post was the grossly incompetent previous repair
that I found.

Can you figure out how the amp ever worked OK afterwards ?



Sure. They got tired of the loud hum and turned it off before any damage
occured. Then someone competent repaired it.


** No way.

The previous repair was done ( almost certainly by a TV tech) in about 1980
and the amp was usable afterwards.



.... Phil

Phil Allison wrote:



The main point of my post was the grossly incompetent previous repair that
I found.

Can you figure out how the amp ever worked OK afterwards ?
Oh, it DIDN'T! But, you already knew that!

Jon

Phil Allison wrote:
"Cydrome Leader"
Phil Allison


** Had an early 1960s guitar amp in this week, a "Maestro
Viscount"
made by
Gibson, aka the GA-16T. All the valves were new, JJ types: 2
x ECC803, 2x
6V6S and a 5Y3.

The accompanying note contained no fault report and asked
only for
two modest modifications:

1. Replace and rewire speaker wire with heavier wire.

2. Rewire to shorten power feed cable from tranny.

The speaker wires were soldered at both ends and just long
enough
to let the
chassis rest on a bench. The AC cable referred to was
internal and
went from
the chassis to a 230V to 115 V step-down fitted in the
factory 50
years ago.
The two wire cable had been wound neatly like a rope and
rested on
the bottom of the case next to the step-down.

The 240V lead was modern, 3 core and there was a wire linking
the
frame of
the step-down to the chassis.

I connected the amp to my Variac and gradually powered it up
to
about 00V - just as I expected it let out an almighty hum,
mostly
50Hz, through
the speaker. The hum mostly disappeared if the volume pot was
turned
down.

Of course bad electros were the cause of the trouble, but the
situation was
not so simple since as someone had been there before me,
decades
ago and substituted two pigtail electros for ones inside a
triple
electro that was
mounted off the chassis on a clamp.

It soon became clear that the third electro in the triple had
now
expired -
but that should cause only 100Hz hum, not 50Hz.

Then came the *shocker*, one of the pigtail electros was
grounded
to the AC
heater supply instead of the chassis - this imposed 3.15
volts AC
at 50Hz on
a DC rail ( the screen supply) that should have had only a
trace of
100Hz ripple.

Removing the dead triple electro, adding a new pigtail one
and
rewiring soon
put things straight leaving only a minor amount of 100Hz buzz
at
full volume.

There was one pigtail electro hanging onto the 5Y3 socket,
grounded
to a lug
on the frame. Soon as I shifted the ground point to the
common
chassis ground, even that hum vanished.

With the amp now working nicely, I modified the speaker and
internal AC leads as requested in the customer's note.

Apparently the customer believed the AC lead tied like a rope
was
causing the hum.

Oh dear..........

It was still an honest repair, so everyone wins. I'm sure it
took
less time to swap the wires than to explain it was something
else.


** Sure - I did what the note asked to avoid an argument and
since
doing it caused no harm, why not ?

Saw this post just now and it reminds me of an incident that
occurred more than 20 years ago. A repair tech friend had grown
rather tired of listening to customers telling him what needed to
be done with their gadgets. Someone brought in a VCR and asked to
have its R/P head replaced. The friend asked about the symptoms
and immediately deduced that the culprit was not the R/P head,
but refrained from making any comment. When the customer came to
collect the VCR later that day, the conversation went like this
(as related to me by another friend who happened to be in the
shop):

Did you replace the head?
Yep.
Is it OK now?
Nope.
Why?
Because that's not the problem.
Then why did you replace the head?
Because you told me to.

Pimpom wrote:
Phil Allison wrote:
"Cydrome Leader"
Phil Allison


** Had an early 1960s guitar amp in this week, a "Maestro
Viscount"
made by
Gibson, aka the GA-16T. All the valves were new, JJ types: 2
x ECC803, 2x
6V6S and a 5Y3.

The accompanying note contained no fault report and asked
only for
two modest modifications:

1. Replace and rewire speaker wire with heavier wire.

2. Rewire to shorten power feed cable from tranny.

The speaker wires were soldered at both ends and just long
enough
to let the
chassis rest on a bench. The AC cable referred to was
internal and
went from
the chassis to a 230V to 115 V step-down fitted in the
factory 50
years ago.
The two wire cable had been wound neatly like a rope and
rested on
the bottom of the case next to the step-down.

The 240V lead was modern, 3 core and there was a wire linking
the
frame of
the step-down to the chassis.

I connected the amp to my Variac and gradually powered it up
to
about 00V - just as I expected it let out an almighty hum,
mostly
50Hz, through
the speaker. The hum mostly disappeared if the volume pot was
turned
down.

Of course bad electros were the cause of the trouble, but the
situation was
not so simple since as someone had been there before me,
decades
ago and substituted two pigtail electros for ones inside a
triple
electro that was
mounted off the chassis on a clamp.

It soon became clear that the third electro in the triple had
now
expired -
but that should cause only 100Hz hum, not 50Hz.

Then came the *shocker*, one of the pigtail electros was
grounded
to the AC
heater supply instead of the chassis - this imposed 3.15
volts AC
at 50Hz on
a DC rail ( the screen supply) that should have had only a
trace of
100Hz ripple.

Removing the dead triple electro, adding a new pigtail one
and
rewiring soon
put things straight leaving only a minor amount of 100Hz buzz
at
full volume.

There was one pigtail electro hanging onto the 5Y3 socket,
grounded
to a lug
on the frame. Soon as I shifted the ground point to the
common
chassis ground, even that hum vanished.

With the amp now working nicely, I modified the speaker and
internal AC leads as requested in the customer's note.

Apparently the customer believed the AC lead tied like a rope
was
causing the hum.

Oh dear..........

It was still an honest repair, so everyone wins. I'm sure it
took
less time to swap the wires than to explain it was something
else.


** Sure - I did what the note asked to avoid an argument and
since
doing it caused no harm, why not ?

Saw this post just now and it reminds me of an incident that
occurred more than 20 years ago. A repair tech friend had grown
rather tired of listening to customers telling him what needed to
be done with their gadgets. Someone brought in a VCR and asked to
have its R/P head replaced. The friend asked about the symptoms
and immediately deduced that the culprit was not the R/P head,
but refrained from making any comment. When the customer came to
collect the VCR later that day, the conversation went like this
(as related to me by another friend who happened to be in the
shop):

Did you replace the head?
Yep.
Is it OK now?
Nope.
Why?
Because that's not the problem.
Then why did you replace the head?
Because you told me to.

Ha.

anybody know what those places that sold replacement heads (nisshoku?)are
doing these days if any survived?

marketing iphone batteries?

anybody know what those places that sold replacement heads (nisshoku?)are doing these days if any survived? marketing iphone batteries?

Many of those companies also supply optics and other assemblies. The market for commercial video heads is still strong. Many studios etc still use tape for the master copy, especially for archiving. 3/4" tape is still very popular.

Dan