When does an amp need a "CAP" job, if it doesn't make noises?

rhythmrocker

1966 Battle of the Bands
Silver Supporting Member
Messages
2,897
If an amp is over 30 years old and DOES NOT make any krackling or weird nosies, how does one know if an amp "needs" a cap job?

Thanks.:D
 

bosstone

Member
Messages
3,399
This topic comes up here about every week and it is like walking through a mine field. For me, I have had fantastic luck about 60 amps in a row, almost all from the 60's through the 80's. If it doesn't make noise and if I don't see any evidence of the caps leaking, I am not going to replace the caps. I have been warned against this policy before but I an not swayed by the argument. If there is an obvious problem, I will take care of it immediately with nothing with parts that are of equal or better quality. I have heard amps with with only minor noise that got cap jobs that came out quieter but poor sound. If you chose to do a cap job, be damned sure to use only premium parts and a tech who knows his business.

I recently sold a 1965 Ampeg Gemini I amp to a studio player in LA. It has ALL original caps. He thought it was a little loud for studio work and took it to his tech. He replaced one preamp tube and switched to a grounded prower wire and now he tells me that the amp is nearly dead quiet.
 

mrface2112

Member
Messages
2,060
it's hard to say, really, especially if they're not showing any physical signs (the aforemention bulging/leaking) or making any noise.

i'm tempted to say "if it looks and sounds fine, don't fix it".

however, you do risk transformer damage if a cap fails in a flamboyant, spectacular way. and with caps that are 15+ years old, that's always a possibility.

so it's a judgement call, really.


cheers,
wade
 

PRNDL

Member
Messages
496
If an amp is over 30 years old and DOES NOT make any krackling or weird nosies, how does one know if an amp "needs" a cap job?

I'd recommend a fair amount of time with the amp on to make certain the caps are good, especially if the amp has not used in a while.
 

Blue Strat

Member
Messages
30,722
Look inside . . . are any of the electrolytic caps bulging or leaking?

This means nothing. I've replaced more bad caps that look perfect than ones that don't.

If the caps are over 20 years old (even less) you replace them. It's like an oil change for your car. You don't wait for the engine to sieze before you change the oil.
 

slider313

Gold Supporting Member
Messages
8,705
This means nothing. I've replaced more bad caps that look perfect than ones that don't.

If the caps are over 20 years old (even less) you replace them. It's like an oil change for your car. You don't wait for the engine to sieze before you change the oil.

+1 Most amps that haven't been used in years may or may not have signs of failing electrolytics. The problem usually is when they DONT show signs and you think it's fine. These amps most likely haven't been used in a rehersal or gig situation, where playing it for a few hours each week would bring a failing cap to the end of it's life and maybe the end of your power transformers life. Mike uses the oil change as an example which is good. I like to think of caps as spark plugs. Would you leave the original plugs in a '65 Mustang? The car may fire up and run, but is it running at it's optimum ?
 

bosstone

Member
Messages
3,399
The problem is with who you have do the work and what caps that get installed. I would rather have an old spark plug that was working fine than having some hack work on it or even a good tech put in some discount store, junk parts, not to mention the wrong parts and I know this happens many, many times. Buyer beware and find a good tech.
 

madstrat

Senior Member
Messages
1,978
yeah man...change those caps

never know what could happen!!!

shoot you might get run over by a bus!!!

these folks seem to know alot more about it than me

but my caps are stayin in my amps from the 70s..until I think they need to go

they are 35 or more years old and they have performed just fine

it's gear for chrissakes!!!...just say a little prayer before you come off standby:crazy

life is full of potential hazards...me and my xfmr's are riding out into the sunset:rotflmao
 

bluessyndicate

Silver Supporting Member
Messages
2,540
I knew my 64 Ampeg Gemini I w/6NS7's needed a cap job the moment I heard a weird sound and my guitar signal faded away and smoke curled up out of the cabinet......
 

blackba

Silver Supporting Member
Messages
12,282
I replaced the caps in my '66 fender champ, they all looked fine, but the amps just sounds alot fuller and smoother with the caps replaced. Its hard to describe the difference, it was like replacing worn out power tubes that you didn't notice were going until you changed them. The tubes remained the same after I changed the caps, so the only thing that changed was the caps.

I would replace the caps in amps built before 1980 in most every case. After that its a case by case basis. I have an '87 Marshall Silver Jubilee that has original caps and I have no plans to change the caps on that amp at this time....
 




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