Vintage Amps and Capacitors ... how do you know?

MykWiz

I would appreciate some feedback from people with more experience on this board.

I've been out doing some research about amps on the web and I keep coming across information regarding capacitors and how they "only last so long" and that "after 10 or 15 years they need to be replaced." My question is how do you know if you have bad capacitors? Will an amp continue to function with bad capacitors? Are there warning signs?

I have a solid state amp (Roland JC-120) that is - as far as I can tell - twenty-some years old. I am pretty sure I want to sell it and pick up my very first tube amp. But I want to know if there is something that I should do proactively to make it more marketable? Or should I just put it up for sale "as is" and not worry about it.

It seems to function perfectly normally to me. Any input you might have on this topic would be greatly appreciated. Thanks!

~MW

SantaStrat · Posted: Sat Jun 28, 2008 3:55 pm Post subject:

Not that I'm a tech, but I see that they are off for the summer, so I will give my tc's worth:

You will know if your amp needs new capacitors when it has run out of its capacity to capacitate. I mean, DUH, DUDE!

....and, you might hear noises: hiss, crackling, yodeling, chortling, or, there may be a loss of power. Those caps can pack a wallop by the way, so don't go testing em with yer tongue or other parts of your exploratory anatomy....

Actually, I only THINK that hiss, loss of power, or smoking, smelling electrical farts etc may be indicators of bad caps.... I'll do a bit of research and report if this is not the case....

I wonder if you had to replace any by now....Your plea was 3 months ago...

I'm pretty sure ALL the techs visiting this forum were on sabbatical at Hooters...

Now if you'd asked about BEER, WOMEN, CARS, GUNS, or ROSE FERTILIZER, ya'd have a HECK of a lot more responses, methinks..... Cool

_________________
I Will if You Will

Herb · Posted: Sat Jun 28, 2008 7:17 pm Post subject:

If your JC-120 is operating normally and not making funny noises or smells, don't bother messing with it. It will be money wasted.
_________________
Yer guitar pickin' friend,
Herb
"It don't mean a thing if it ain't got that swing, 'n stuff!"
Doghouse Jazz

tele savalas · Posted: Sun Jun 29, 2008 3:39 am Post subject:

Chortling and farts - that's the key, right there.

Chortling and farts.

If it doesn't chortle and doesn't smell like something crawled up in it and died, leave it alone.
_________________
Who loves ya, baby?

gehen.wir · Sea Monkey Joined: 26 May 2008 Posts: 12

You're right about the life span: 10 - 15 years for your FILTER capacitors. If you have a tube amp, these are the cylinders (LCR on Marshalls) that are mounted on the chassis on the same side as the tubes, power transformers, chokes, etc.

Signs that you need to change them:

1. You'll have to visually inspect them. Bubbles are the first signs that you need to change them NOW before something catastrophic occurs.

2. Bass is not tight, loose, flubby, <insert adjective>.

I have a 1987 Marshall Jubilee and even though the bubbles did not occur on the filter caps, the bass was not tight. I was advised to change them ASAP. I did the swap myself, and I'm glad I did.

You don't have to change the electrolytic capacitors mounted on the circuit board (these are the small cylinders that have a vertical stripe of a different color, denotiing the NEGATIVE side).

All the best,

Gehen Wir

MykWiz · Posted: Mon Jun 30, 2008 2:30 pm Post subject:

Thanks guys!

I thought I was just the resident post-killer. I have done that in other posts it seems -- I make a comment and then NO ONE makes one after me -- I thought it was my own unique talent.

And then again I also thought it was maybe a "newbie" question that was so stupid it didn't deserve a reply. Theatre of the mind can be pretty cruel at times! Smile

Again, I appreciate the feedback!

~MW