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  #1   Report Post  
Scott Dorsey
 
Posts: n/a
Default Spin from Bipolar caps

Wayne wrote:
This may be a little OT, but it still has to do with caps.

I've got a Fender '65 Twin thats got old GE paper electrolytics in the B+
circuit.
Most are 20uf @ 450 volts. I'm a relunctant to replace those with NOS for the
obvious reasons the NOS probably are not gonna be an improvement over whats in
there now.


NOS caps will probably be worse, since they will have been sitting on the
shelf for a long time.

First. Is it advisable to replace with something else, since technology
changes and this is 40 year old design.?


If you change them with a modern technology cap, the amp will sound different.
This could be good or bad. If you replace them with a new cap of old
design (Antique Electronics Supply has a nice selection), it will sound
much the same.

Second, I'm having problems finding new replacements because of the 450v
requirement.


Panasonic makes some modern ones. Mallory I think makes some old ones.
Are these metal can types? Personally I would go to a 600V one for
somewhat longer life.

Third, should I also replace all those .1mfd and .047mfd while I'm at it and
with what?


If they are paper caps, putting anything else in there will change the
sound but improve reliability.

BTW, I'm really not interested in changing the "sound" of the Twin. It's a
great amp as is!!! Just wanting to clean up some of the hum, etc.


Anything you do will change the sound, which is the problem.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
  #2   Report Post  
Scott Dorsey
 
Posts: n/a
Default

Wayne wrote:
This may be a little OT, but it still has to do with caps.

I've got a Fender '65 Twin thats got old GE paper electrolytics in the B+
circuit.
Most are 20uf @ 450 volts. I'm a relunctant to replace those with NOS for the
obvious reasons the NOS probably are not gonna be an improvement over whats in
there now.


NOS caps will probably be worse, since they will have been sitting on the
shelf for a long time.

First. Is it advisable to replace with something else, since technology
changes and this is 40 year old design.?


If you change them with a modern technology cap, the amp will sound different.
This could be good or bad. If you replace them with a new cap of old
design (Antique Electronics Supply has a nice selection), it will sound
much the same.

Second, I'm having problems finding new replacements because of the 450v
requirement.


Panasonic makes some modern ones. Mallory I think makes some old ones.
Are these metal can types? Personally I would go to a 600V one for
somewhat longer life.

Third, should I also replace all those .1mfd and .047mfd while I'm at it and
with what?


If they are paper caps, putting anything else in there will change the
sound but improve reliability.

BTW, I'm really not interested in changing the "sound" of the Twin. It's a
great amp as is!!! Just wanting to clean up some of the hum, etc.


Anything you do will change the sound, which is the problem.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
  #3   Report Post  
S O'Neill
 
Posts: n/a
Default

Wayne wrote:


I've got a Fender '65 Twin thats got old GE paper electrolytics in
the B+ circuit. Most are 20uf @ 450 volts. I'm a relunctant to
replace those with NOS for the obvious reasons the NOS probably are
not gonna be an improvement over whats in there now.



Brand new ones will be fine. www.tubesandmore.com

Yours should have had 525-volt, since there's more than 450 volts on them.


First. Is it advisable to replace with something else, since
technology changes and this is 40 year old design.?



Sure.


Second, I'm having problems finding new replacements because of the
450v requirement.



450's are stocked about everywhere, like www.mouser.com. But you should
use a higher rating.


Third, should I also replace all those .1mfd and .047mfd while I'm at
it and with what?



Not if they're not causing a problem.


BTW, I'm really not interested in changing the "sound" of the Twin.
It's a great amp as is!!! Just wanting to clean up some of the hum,
etc.



Therefore you *should* replace the power supply filters; do the 50
that's in the bias supply too.



I can solder and do the light stuff, but I'm not an schooled in
electronics.



Since lethal voltages are present, don't even start this yourself. Take
it in to someone who won't get killed.



  #4   Report Post  
S O'Neill
 
Posts: n/a
Default

Wayne wrote:


I've got a Fender '65 Twin thats got old GE paper electrolytics in
the B+ circuit. Most are 20uf @ 450 volts. I'm a relunctant to
replace those with NOS for the obvious reasons the NOS probably are
not gonna be an improvement over whats in there now.



Brand new ones will be fine. www.tubesandmore.com

Yours should have had 525-volt, since there's more than 450 volts on them.


First. Is it advisable to replace with something else, since
technology changes and this is 40 year old design.?



Sure.


Second, I'm having problems finding new replacements because of the
450v requirement.



450's are stocked about everywhere, like www.mouser.com. But you should
use a higher rating.


Third, should I also replace all those .1mfd and .047mfd while I'm at
it and with what?



Not if they're not causing a problem.


BTW, I'm really not interested in changing the "sound" of the Twin.
It's a great amp as is!!! Just wanting to clean up some of the hum,
etc.



Therefore you *should* replace the power supply filters; do the 50
that's in the bias supply too.



I can solder and do the light stuff, but I'm not an schooled in
electronics.



Since lethal voltages are present, don't even start this yourself. Take
it in to someone who won't get killed.



  #5   Report Post  
Paul Stamler
 
Posts: n/a
Default


"Wayne" wrote in message
...
This may be a little OT, but it still has to do with caps.

I've got a Fender '65 Twin thats got old GE paper electrolytics in the B+
circuit.
Most are 20uf @ 450 volts. I'm a relunctant to replace those with NOS for

the
obvious reasons the NOS probably are not gonna be an improvement over

whats in
there now.


Correct. They're likely to be just as bad, maybe worse.

First. Is it advisable to replace with something else, since technology
changes and this is 40 year old design.?

Second, I'm having problems finding new replacements because of the 450v
requirement.

Third, should I also replace all those .1mfd and .047mfd while I'm at it

and
with what?

BTW, I'm really not interested in changing the "sound" of the Twin. It's

a
great amp as is!!! Just wanting to clean up some of the hum, etc.


The problem is, you *are* going to change the sound. Why? Because as the
capacitors have aged, you've gotten used to the sound of an amp with bad,
saggy, worn out supply caps. When you replace them with caps that actually
do what they're supposed to, you'll hear a different sound, probably pretty
close to what the amp sounded like when it was new (discounting the changes
in the speakers, of course).

So you're going to change it; sorry, that's just the way life is sometimes.
You can get new caps various places; Panasonic makes a 33uF 450V one (TSUP
series), and they have some other TSxx 450V series with higher temperature
ratings, which will improve reliability, but they're all bigger than 33uF. I
would like that (nice tight bass) but it'll further change the sound, and
you might not like it. Panasonic caps are available at Digi-Key
(www.digikey.com).

Or you can get something a lot closer to what Fender used from Antique
Electronic Supply (www.tubesandmore.com). I'd stay away from the NOS stuff,
though; as you noted, it probably won't clean your hum up.

Peace,
Paul




  #6   Report Post  
Paul Stamler
 
Posts: n/a
Default


"Wayne" wrote in message
...
This may be a little OT, but it still has to do with caps.

I've got a Fender '65 Twin thats got old GE paper electrolytics in the B+
circuit.
Most are 20uf @ 450 volts. I'm a relunctant to replace those with NOS for

the
obvious reasons the NOS probably are not gonna be an improvement over

whats in
there now.


Correct. They're likely to be just as bad, maybe worse.

First. Is it advisable to replace with something else, since technology
changes and this is 40 year old design.?

Second, I'm having problems finding new replacements because of the 450v
requirement.

Third, should I also replace all those .1mfd and .047mfd while I'm at it

and
with what?

BTW, I'm really not interested in changing the "sound" of the Twin. It's

a
great amp as is!!! Just wanting to clean up some of the hum, etc.


The problem is, you *are* going to change the sound. Why? Because as the
capacitors have aged, you've gotten used to the sound of an amp with bad,
saggy, worn out supply caps. When you replace them with caps that actually
do what they're supposed to, you'll hear a different sound, probably pretty
close to what the amp sounded like when it was new (discounting the changes
in the speakers, of course).

So you're going to change it; sorry, that's just the way life is sometimes.
You can get new caps various places; Panasonic makes a 33uF 450V one (TSUP
series), and they have some other TSxx 450V series with higher temperature
ratings, which will improve reliability, but they're all bigger than 33uF. I
would like that (nice tight bass) but it'll further change the sound, and
you might not like it. Panasonic caps are available at Digi-Key
(www.digikey.com).

Or you can get something a lot closer to what Fender used from Antique
Electronic Supply (www.tubesandmore.com). I'd stay away from the NOS stuff,
though; as you noted, it probably won't clean your hum up.

Peace,
Paul


  #7   Report Post  
Wayne
 
Posts: n/a
Default

Brand new ones will be fine. www.tubesandmore.com

Yours should have had 525-volt, since there's more than 450 volts on them.



You're right. It's the AB763 schematic which specifies 525. Most of the
working voltages are around 450.

There's also some 25/25 in there. I'll probably just change the 20/525's, the
50/50 in the bias circuit and the 25/25's.

Thanks for the hi-voltage warning, but I'm already familiar with that. I
usually just unplug from the wall and do the screwdriver to chassis welding
function. I used to work on microwave ovens and those trash cans can flat ruin
your day alright.

Thanks for the help


--Wayne

-"sounded good to me"-
  #8   Report Post  
Wayne
 
Posts: n/a
Default

Brand new ones will be fine. www.tubesandmore.com

Yours should have had 525-volt, since there's more than 450 volts on them.



You're right. It's the AB763 schematic which specifies 525. Most of the
working voltages are around 450.

There's also some 25/25 in there. I'll probably just change the 20/525's, the
50/50 in the bias circuit and the 25/25's.

Thanks for the hi-voltage warning, but I'm already familiar with that. I
usually just unplug from the wall and do the screwdriver to chassis welding
function. I used to work on microwave ovens and those trash cans can flat ruin
your day alright.

Thanks for the help


--Wayne

-"sounded good to me"-
  #9   Report Post  
Arny Krueger
 
Posts: n/a
Default

"Wayne" wrote in message

Brand new ones will be fine. www.tubesandmore.com

Yours should have had 525-volt, since there's more than 450 volts on
them.



You're right. It's the AB763 schematic which specifies 525. Most of
the working voltages are around 450.

There's also some 25/25 in there. I'll probably just change the
20/525's, the 50/50 in the bias circuit and the 25/25's.

Thanks for the hi-voltage warning, but I'm already familiar with
that. I usually just unplug from the wall and do the screwdriver to
chassis welding function. I used to work on microwave ovens and
those trash cans can flat ruin your day alright.


That's why God invented 100 ohm 5 watt resistors - they take the sting out
of the *welding function*.


  #10   Report Post  
Arny Krueger
 
Posts: n/a
Default

"Wayne" wrote in message

Brand new ones will be fine. www.tubesandmore.com

Yours should have had 525-volt, since there's more than 450 volts on
them.



You're right. It's the AB763 schematic which specifies 525. Most of
the working voltages are around 450.

There's also some 25/25 in there. I'll probably just change the
20/525's, the 50/50 in the bias circuit and the 25/25's.

Thanks for the hi-voltage warning, but I'm already familiar with
that. I usually just unplug from the wall and do the screwdriver to
chassis welding function. I used to work on microwave ovens and
those trash cans can flat ruin your day alright.


That's why God invented 100 ohm 5 watt resistors - they take the sting out
of the *welding function*.




  #11   Report Post  
Geoff Wood
 
Posts: n/a
Default


"Paul Stamler" wrote in message news:Eu1sd.86067
The problem is, you *are* going to change the sound. Why? Because as the
capacitors have aged, you've gotten used to the sound of an amp with bad,
saggy, worn out supply caps. When you replace them with caps that actually
do what they're supposed to, you'll hear a different sound, probably
pretty
close to what the amp sounded like when it was new (discounting the
changes
in the speakers, of course).


A bit like changing your guitar strings really !

geoff


  #12   Report Post  
Geoff Wood
 
Posts: n/a
Default


"Paul Stamler" wrote in message news:Eu1sd.86067
The problem is, you *are* going to change the sound. Why? Because as the
capacitors have aged, you've gotten used to the sound of an amp with bad,
saggy, worn out supply caps. When you replace them with caps that actually
do what they're supposed to, you'll hear a different sound, probably
pretty
close to what the amp sounded like when it was new (discounting the
changes
in the speakers, of course).


A bit like changing your guitar strings really !

geoff


  #13   Report Post  
S O'Neill
 
Posts: n/a
Default

Arny Krueger wrote:

"Wayne" wrote in message


Thanks for the hi-voltage warning, but I'm already familiar with
that. I usually just unplug from the wall and do the screwdriver to
chassis welding function. I used to work on microwave ovens and
those trash cans can flat ruin your day alright.



That's why God invented 100 ohm 5 watt resistors - they take the sting out
of the *welding function*.


Well, Leo already gave you some, just turn the Standby switch on after
you've turned the power off, there are bleeder resistors on the two
70-uF filter input caps.


  #14   Report Post  
S O'Neill
 
Posts: n/a
Default

Arny Krueger wrote:

"Wayne" wrote in message


Thanks for the hi-voltage warning, but I'm already familiar with
that. I usually just unplug from the wall and do the screwdriver to
chassis welding function. I used to work on microwave ovens and
those trash cans can flat ruin your day alright.



That's why God invented 100 ohm 5 watt resistors - they take the sting out
of the *welding function*.


Well, Leo already gave you some, just turn the Standby switch on after
you've turned the power off, there are bleeder resistors on the two
70-uF filter input caps.


  #15   Report Post  
sycochkn
 
Posts: n/a
Default

If the caps are old they my no longer be 20 uf @ 450 volts should not be
that hard to find. Be wary of tantalum caps since the failure mode is to
chatch on fire. Go for the aluminum electrolytics, they just explode or go
open.

Bob

"Wayne" wrote in message
...
This may be a little OT, but it still has to do with caps.

I've got a Fender '65 Twin thats got old GE paper electrolytics in the B+
circuit.
Most are 20uf @ 450 volts. I'm a relunctant to replace those with NOS for

the
obvious reasons the NOS probably are not gonna be an improvement over

whats in
there now.

First. Is it advisable to replace with something else, since technology
changes and this is 40 year old design.?

Second, I'm having problems finding new replacements because of the 450v
requirement.

Third, should I also replace all those .1mfd and .047mfd while I'm at it

and
with what?

BTW, I'm really not interested in changing the "sound" of the Twin. It's

a
great amp as is!!! Just wanting to clean up some of the hum, etc.

I can solder and do the light stuff, but I'm not an schooled in

electronics.

Thanks,

--Wayne

-"sounded good to me"-





  #16   Report Post  
sycochkn
 
Posts: n/a
Default

If the caps are old they my no longer be 20 uf @ 450 volts should not be
that hard to find. Be wary of tantalum caps since the failure mode is to
chatch on fire. Go for the aluminum electrolytics, they just explode or go
open.

Bob

"Wayne" wrote in message
...
This may be a little OT, but it still has to do with caps.

I've got a Fender '65 Twin thats got old GE paper electrolytics in the B+
circuit.
Most are 20uf @ 450 volts. I'm a relunctant to replace those with NOS for

the
obvious reasons the NOS probably are not gonna be an improvement over

whats in
there now.

First. Is it advisable to replace with something else, since technology
changes and this is 40 year old design.?

Second, I'm having problems finding new replacements because of the 450v
requirement.

Third, should I also replace all those .1mfd and .047mfd while I'm at it

and
with what?

BTW, I'm really not interested in changing the "sound" of the Twin. It's

a
great amp as is!!! Just wanting to clean up some of the hum, etc.

I can solder and do the light stuff, but I'm not an schooled in

electronics.

Thanks,

--Wayne

-"sounded good to me"-



  #17   Report Post  
Phil Allison
 
Posts: n/a
Default


"Wayne"
This may be a little OT, but it still has to do with caps.

I've got a Fender '65 Twin thats got old GE paper electrolytics in the B+
circuit.
Most are 20uf @ 450 volts. I'm a relunctant to replace those with NOS for
the
obvious reasons the NOS probably are not gonna be an improvement over
whats in
there now.

BTW, I'm really not interested in changing the "sound" of the Twin. It's
a
great amp as is!!! Just wanting to clean up some of the hum, etc.



** Your hum may easily be due to the pre-amp tubes or defective grounding
of the heater supply.

Take it to an amp tech and don't make it a nightmare out of it for him by
messing with it first.




............ Phil





  #18   Report Post  
Phil Allison
 
Posts: n/a
Default


"Wayne"
This may be a little OT, but it still has to do with caps.

I've got a Fender '65 Twin thats got old GE paper electrolytics in the B+
circuit.
Most are 20uf @ 450 volts. I'm a relunctant to replace those with NOS for
the
obvious reasons the NOS probably are not gonna be an improvement over
whats in
there now.

BTW, I'm really not interested in changing the "sound" of the Twin. It's
a
great amp as is!!! Just wanting to clean up some of the hum, etc.



** Your hum may easily be due to the pre-amp tubes or defective grounding
of the heater supply.

Take it to an amp tech and don't make it a nightmare out of it for him by
messing with it first.




............ Phil





  #19   Report Post  
Pooh Bear
 
Posts: n/a
Default

Scott Dorsey wrote:

Wayne wrote:
This may be a little OT, but it still has to do with caps.

I've got a Fender '65 Twin thats got old GE paper electrolytics in the B+
circuit.
Most are 20uf @ 450 volts. I'm a relunctant to replace those with NOS for the
obvious reasons the NOS probably are not gonna be an improvement over whats in
there now.


NOS caps will probably be worse, since they will have been sitting on the
shelf for a long time.

First. Is it advisable to replace with something else, since technology
changes and this is 40 year old design.?


If you change them with a modern technology cap, the amp will sound different.
This could be good or bad. If you replace them with a new cap of old
design (Antique Electronics Supply has a nice selection), it will sound
much the same.

Second, I'm having problems finding new replacements because of the 450v
requirement.


Panasonic makes some modern ones. Mallory I think makes some old ones.
Are these metal can types? Personally I would go to a 600V one for
somewhat longer life.

Third, should I also replace all those .1mfd and .047mfd while I'm at it and
with what?


If they are paper caps, putting anything else in there will change the
sound but improve reliability.

BTW, I'm really not interested in changing the "sound" of the Twin. It's a
great amp as is!!! Just wanting to clean up some of the hum, etc.


Anything you do will change the sound, which is the problem.


OTOH you may be well pleased with the changed sound !

I had a few original Vox AC30s in for repairs many years ( decades ) back.

Most of the problems were 'burnt out' 100k anode / plate resistors and horrible
'Hunts' 0.01uF coupling caps that degrade with time to the extent that the plastic
case would literally 'crumble' like dry bread !

Relaced those parts with new stock of modern characteristics - e.g. metal oxide /
film Rs and plastic film caps.

Also found a poor output stage biasing problem ( used cathode bias alone ) that
meant that the 2 paralled EL84s on each side of the push-pull arrangement ( 4 x
EL84s total ) shared -ve bias and therefore there was no way of assuring any remote
chance of matching Ia. Changed this to a proper individual bias arrangement.

The owners were well pleased with the results. It was like giving the amps a new
lease of life and a breath of fresh air.


Graham

  #20   Report Post  
Pooh Bear
 
Posts: n/a
Default

Scott Dorsey wrote:

Wayne wrote:
This may be a little OT, but it still has to do with caps.

I've got a Fender '65 Twin thats got old GE paper electrolytics in the B+
circuit.
Most are 20uf @ 450 volts. I'm a relunctant to replace those with NOS for the
obvious reasons the NOS probably are not gonna be an improvement over whats in
there now.


NOS caps will probably be worse, since they will have been sitting on the
shelf for a long time.

First. Is it advisable to replace with something else, since technology
changes and this is 40 year old design.?


If you change them with a modern technology cap, the amp will sound different.
This could be good or bad. If you replace them with a new cap of old
design (Antique Electronics Supply has a nice selection), it will sound
much the same.

Second, I'm having problems finding new replacements because of the 450v
requirement.


Panasonic makes some modern ones. Mallory I think makes some old ones.
Are these metal can types? Personally I would go to a 600V one for
somewhat longer life.

Third, should I also replace all those .1mfd and .047mfd while I'm at it and
with what?


If they are paper caps, putting anything else in there will change the
sound but improve reliability.

BTW, I'm really not interested in changing the "sound" of the Twin. It's a
great amp as is!!! Just wanting to clean up some of the hum, etc.


Anything you do will change the sound, which is the problem.


OTOH you may be well pleased with the changed sound !

I had a few original Vox AC30s in for repairs many years ( decades ) back.

Most of the problems were 'burnt out' 100k anode / plate resistors and horrible
'Hunts' 0.01uF coupling caps that degrade with time to the extent that the plastic
case would literally 'crumble' like dry bread !

Relaced those parts with new stock of modern characteristics - e.g. metal oxide /
film Rs and plastic film caps.

Also found a poor output stage biasing problem ( used cathode bias alone ) that
meant that the 2 paralled EL84s on each side of the push-pull arrangement ( 4 x
EL84s total ) shared -ve bias and therefore there was no way of assuring any remote
chance of matching Ia. Changed this to a proper individual bias arrangement.

The owners were well pleased with the results. It was like giving the amps a new
lease of life and a breath of fresh air.


Graham



  #21   Report Post  
Pooh Bear
 
Posts: n/a
Default

Phil Allison wrote:

"Wayne"
This may be a little OT, but it still has to do with caps.

I've got a Fender '65 Twin thats got old GE paper electrolytics in the B+
circuit.
Most are 20uf @ 450 volts. I'm a relunctant to replace those with NOS for
the
obvious reasons the NOS probably are not gonna be an improvement over
whats in
there now.

BTW, I'm really not interested in changing the "sound" of the Twin. It's
a
great amp as is!!! Just wanting to clean up some of the hum, etc.


** Your hum may easily be due to the pre-amp tubes or defective grounding
of the heater supply.

Take it to an amp tech and don't make it a nightmare out of it for him by
messing with it first.


Amen to " don't make it a nightmare out of it for him by messing with it first "
!

If only ppl would respect their limitations. Seen some weird **** done to gear.


Graham

  #22   Report Post  
Pooh Bear
 
Posts: n/a
Default

Phil Allison wrote:

"Wayne"
This may be a little OT, but it still has to do with caps.

I've got a Fender '65 Twin thats got old GE paper electrolytics in the B+
circuit.
Most are 20uf @ 450 volts. I'm a relunctant to replace those with NOS for
the
obvious reasons the NOS probably are not gonna be an improvement over
whats in
there now.

BTW, I'm really not interested in changing the "sound" of the Twin. It's
a
great amp as is!!! Just wanting to clean up some of the hum, etc.


** Your hum may easily be due to the pre-amp tubes or defective grounding
of the heater supply.

Take it to an amp tech and don't make it a nightmare out of it for him by
messing with it first.


Amen to " don't make it a nightmare out of it for him by messing with it first "
!

If only ppl would respect their limitations. Seen some weird **** done to gear.


Graham

  #23   Report Post  
Wayne
 
Posts: n/a
Default

Go for the aluminum electrolytics, they just explode or go
open.

Bob


I ordered all Sprague Atom caps from Triode Electronics. Had to go with the
500v instead of 600v cause they don't fit under the shield.

Thanks to all for your help.

--Wayne

-"sounded good to me"-
  #24   Report Post  
Wayne
 
Posts: n/a
Default

Go for the aluminum electrolytics, they just explode or go
open.

Bob


I ordered all Sprague Atom caps from Triode Electronics. Had to go with the
500v instead of 600v cause they don't fit under the shield.

Thanks to all for your help.

--Wayne

-"sounded good to me"-
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