25/25 caps in a 72 Champ

radarman · May 7th, 2005, 07:56 PM

Was wondering if anyone knows what the original 25/25 electrolytic capzapitors look like. My 72 Champ has three white Mallory 25/25 electrolytics. I think these are stock. Should they really be changed?

Thanks.

EMan · May 7th, 2005, 08:20 PM

The old white and blue tubular caps are pretty tough. My '62 Princeton still has it's OEM coupling/tone caps.

I'm of the 'don't fix it if it ain't broke' mentality...and if the caps don't look bad (leaking/buldging) leave them in there.

Depending on your degree of concern, you can always slap them across a cap checker.

Keep in mind that caps that drift in the positive direction...as in larger than 25uF - won't affect the tone noticably.

The cathode R/C's in most Fender amps in the cathode circuits have a low frequency roll off of about 8Hz (3db).

radarman · May 7th, 2005, 09:57 PM

The caps look like new and have no shape deformation. The amp sat for many years which might be why they are in such good shape. Thanks for the input EMan.
:)

AtomicMassUnit · May 8th, 2005, 12:37 PM

I haven't seen too many of those white electrolytics have problems. As long as it sounds good, you'll probably be ok leaving those in with the exception of the bypass cap for the 6V6. These take a lot of heat and the amp would probably benefit from a new one here. Also keep an eye on your filter caps. If you can safely discharge your caps and can solder, a champ would be a really good place to start learning about repairs and maintenance. Go for it.

Atomic

jjmantele · May 8th, 2005, 11:14 PM

I changed mine when I got my '74 VC. It's "recommended" as part of a standard 10-20 year tune-up. Yours are on 33 years now. The one on the 6v6 has 24VDC on it according to the AB764 schematic which is too close to the 25VDC rating for me. A 50VDC cap costs the same usually so I used one in that position. Save the originals for posterity.

Rob DiStefano · May 9th, 2005, 07:16 AM

Quote:

Originally Posted by jjmantele

... The one on the 6v6 has 24VDC on it according to the AB764 schematic which is too close to the 25VDC rating for me. A 50VDC cap costs the same usually so I used one in that position. Save the originals for posterity.

I agree - go with the higher voltage caps. But I just throw out the old 25v ones. 8)

May 7th, 2005, 07:56 PM	#1 (permalink)
radarman Tele-Meister Join Date: Jan 2005 Location: Colorado Posts: 319	25/25 caps in a 72 Champ Was wondering if anyone knows what the original 25/25 electrolytic capzapitors look like. My 72 Champ has three white Mallory 25/25 electrolytics. I think these are stock. Should they really be changed? Thanks. __________________ One man alone can be pretty dumb sometimes, but for real bona fide stupidity, there ain't nothin' can beat teamwork. Edward Abbey

May 7th, 2005, 09:57 PM	#3 (permalink)
radarman Tele-Meister Join Date: Jan 2005 Location: Colorado Posts: 319	Think I will leave them in The caps look like new and have no shape deformation. The amp sat for many years which might be why they are in such good shape. Thanks for the input EMan. :) __________________ One man alone can be pretty dumb sometimes, but for real bona fide stupidity, there ain't nothin' can beat teamwork. Edward Abbey

May 8th, 2005, 11:14 PM	#5 (permalink)
jjmantele Tele-Holic Join Date: Aug 2003 Location: New Jersey Posts: 851	cathode caps I changed mine when I got my '74 VC. It's "recommended" as part of a standard 10-20 year tune-up. Yours are on 33 years now. The one on the 6v6 has 24VDC on it according to the AB764 schematic which is too close to the 25VDC rating for me. A 50VDC cap costs the same usually so I used one in that position. Save the originals for posterity. __________________ JJman If it says "Vintage" on it -it isn't.

May 7th, 2005, 08:20 PM	#2 (permalink)
EMan Tele-Holic Join Date: Apr 2003 Location: Dallas, Texas Posts: 939	The old white and blue tubular caps are pretty tough. My '62 Princeton still has it's OEM coupling/tone caps. I'm of the 'don't fix it if it ain't broke' mentality...and if the caps don't look bad (leaking/buldging) leave them in there. Depending on your degree of concern, you can always slap them across a cap checker. Keep in mind that caps that drift in the positive direction...as in larger than 25uF - won't affect the tone noticably. The cathode R/C's in most Fender amps in the cathode circuits have a low frequency roll off of about 8Hz (3db).

May 8th, 2005, 12:37 PM	#4 (permalink)
AtomicMassUnit Tele-Meister Join Date: Apr 2003 Posts: 153	I haven't seen too many of those white electrolytics have problems. As long as it sounds good, you'll probably be ok leaving those in with the exception of the bypass cap for the 6V6. These take a lot of heat and the amp would probably benefit from a new one here. Also keep an eye on your filter caps. If you can safely discharge your caps and can solder, a champ would be a really good place to start learning about repairs and maintenance. Go for it. Atomic