Which Brand Electrolytic Caps for Fender AB763? - diyAudio
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Old 3rd December 2012, 11:52 PM   #1
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Default Which Brand Electrolytic Caps for Fender AB763?

The five electrolytic caps (under the metal dome) on my dad's AB763 are fifty years old, leaking & smoking--they need replacement.

Which make/model of electrolytic capacitors should I replace them with? Or does it matter? I am guessing it matters. 20MFD 500VDC x 3 , 70MFD @ 350VDC x 2 are currently in it.
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Old 4th December 2012, 07:51 AM   #2
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Quote:
Originally Posted by audiogeekess View Post
Which make/model of electrolytic capacitors should I replace them with? Or does it matter? I am guessing it matters.
No, not at all - the values aren't very critical either.

The problem is likely to be finding suitable replacements, not having a plethora of choices
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Old 4th December 2012, 04:57 PM   #3
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Some people are inclined to use a high quality cap like a sprague. A inexpensive chinese unit will work but may not be the right choice for a collectable nice amp like that.
If it was mine I would not be afraid to use a inexpensive unit if I had the correct ones laying around. But, if it was a customer's I would have them step up for the good ones. Come-backs suck!

try these http://thetubestore.com/sprague.html

Last edited by jeeptechfred; 4th December 2012 at 05:02 PM.
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Old 4th December 2012, 08:26 PM   #4
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I would stick close to the values. Useing the link provided I would use three 20uf 500v and two 80uf 450v. Measure to make sure new ones will fit.

Last edited by jeeptechfred; 4th December 2012 at 08:32 PM.
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Old 4th December 2012, 08:55 PM   #5
Trout is offline Trout  United States
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With all due respect to Sprague, they are no longer any better than others in the industry.

In fact, if you cut open the current production Sprague Atoms they are nothing more than a tiny component inside a needlessly big can.

Best bang for the buck these days in guitar amp caps are F&T.
They make a great 22uf/500V as well as 80uf/450V

You might end up a tiny stiffer in the supply but from a cost effectiveness standpoint,
Spragues = $55.00-$65.00 for all 5 caps
F & T = $30.00-$35.00 for all 5 caps

Exact values will be difficult to locate since even sprague vendors do not seem to stock the original values anymore.
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Old 4th December 2012, 09:06 PM   #6
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I like IC- Illinois Capacitor, but I'm not sure it makes much difference. I'd stay very close to factory values.
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Old 5th December 2012, 02:14 AM   #7
Trout is offline Trout  United States
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Quote:
Originally Posted by Conrad Hoffman View Post
I like IC- Illinois Capacitor, but I'm not sure it makes much difference. I'd stay very close to factory values.

I have used IC's on several occasions and had no complaints at all with them.
They are in most cases even lower cost than F&T.

That Said,
not long ago they were pretty much thought of as junk after a couple bad runs that landed in Fender Blues Deluxes or Blues Juniors, I forget which.

Lots of pictures on the web of failed ones from back than.
Click the image to open in full size.
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Old 5th December 2012, 08:48 PM   #8
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great info. Thanks for your additions to my post. I learned something, cool!
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Old 8th December 2012, 01:32 AM   #9
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Thanks for all the replies. I ended up going with a set of F&T's.

I installed them correctly and checked all my solder joints. The amp won't turn on. The power light doesn't turn on and the fuse is good. It's getting AC voltage at the input--I measured that. The three smaller caps get charged up with like 7-17 volts and the 2 bigger ones I've seen at a few volts--after turning off.

I don't know what was damaged the last time it was turned out (it was smoking from the bad caps).. I figured it would be working again after replacing the caps.. sigh.

Well thanks again for the help.
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Old 8th December 2012, 07:58 AM   #10
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The two 70uF should have 450V odd across them (half across each), if not there's VERY little that can be wrong, transformer or rectifiers basically.
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