Replacing caps in vintage amps, yay or nay?

[VonBonfire]

Interesting. FWIW (This post was 15 years ago)

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Right, they rarely fail because most owners rarely put their stuff through hard use let alone even use it regularly at all. I'd be having it fully recapped AND having every solder joint on the turret reflowed AND have my cathode bypass resistors replaced pre-emptively just cause if your cathode bypass resistors go and it requires an emergency fix you will have one harsh sounding amp at your next gig until they burn in. You can either limp the thing from failure to failure until it's fully rebuilt or you can rebuild it into a tuned machine right out of the gate but $$$. The joy of getting a reliable vintage amp.

 

[midnightlaundry]

When I played Mesa, I did have a Filter Cap fail in my 290 Power Amp. It took out some Resistors and my Choke Filter with it..
It was 2 OG blue Sprague's they used back then.. I don't know how I managed to fix it because I don't know shit. I really didn't know shit back then..

From the archives..

 

[midnightlaundry]

They say when Filter Caps start to go you get motor boating sounds because they aren't filtering the ripple any longer..
Unless you want the experience, it ain't broke..

 

[Bad Brain]

Sounds like the prudent choice (Especially if it's your money maker) is to replace the caps. I don't see a downside other than loss of bragging rights

 

[JohnnyGtar]

If play regularly, amp sounds good, no leaks/bulging, would you still replace just to be safe? And by vintage, I mean 40 yrs +.

Good lord, yes. Replace them and don't turn that amp on again until you do.

 

[JohnnyGtar]

Um, yes. Especially in a vintage amp with an unobtainable tranny. A Mercury Magnetics tranny in a 61' Brown Deluxe turns a $2500 amp into a $500 amp.

Yep. This.

 

[Racerxrated]

I change em when they need them.

Play the gear regularly....they will last and last and last.

Yep.

Gigged a bunch with mostly JCM/JMP Marshalls, no failures yet with OG Dalys/LCRs. Only 1 Vintage Marshall needed them; as they were starting to leak powder out of the bottoms. I've changed a few others, but only to hear/feel the difference with lower values in the PI/Preamp sections.
Larry himself said "Vintage Daly and LCR caps seem to have unnatural long life." Which is why he uses vintage LCRs in all his builds.

As Hard Driver said, you can measure them to see how they are. If you do replace them in a vintage amp, save them as they can be re formed, a future buyer may value them if you sell the amp.

One thing I'd mention, if you have a vintage Marshall I'd highly recommend using ARS IF you decide to change them. They look and sound just like the OG LCRs/Dalys. I've noticed a slight difference when I've played Marshalls with F&T caps. Very subtle, but the decay to the notes/chords sounded strange to me. Happened a few times, first with a Jubilee 2555 and next an 82 2204. Swapped in ARS, and that fixed it.

With other brands/builds, I'd be more careful as I don't have much experience with amps not named Marshall/Mesa. I'd probably just change them without hesitation. Mesas, Mike B always changes the can caps if he services the amp.

 

[blackba]

The 10uf/100V bias supply filter caps should definitely be changed even if the even if you decide the keep the 50/50uf Daly caps for the mains screens and phase inverter if they are in good shape.

If those bias supply cap go while the amp is operating it can take out tubes and an output transformer and ya don't want that. If those are still original Eries those should be changed for sure.

I would think originals from 1978 are at the end of their lifespan for sure.

When I am changing the bias cap or caps, I now just change the bias diode. I have seen enough leak and its a 10cent 1N4007 diode, so I figure why not. the cause of my 2553 marshall silver jubilee redplating was a leaking bias diode. Had I changed it when I did the recap a few years prior, I would have avoided the issue.

 

[harddriver]

When I am changing the bias cap or caps, I now just change the bias diode. I have seen enough leak and its a 10cent 1N4007 diode, so I figure why not. the cause of my 2553 marshall silver jubilee redplating was a leaking bias diode. Had I changed it when I did the recap a few years prior, I would have avoided the issue.

That's some really good information to have in the back pocket for future reference! Thanks for adding that!

 

[glpg80]

When I am changing the bias cap or caps, I now just change the bias diode. I have seen enough leak and its a 10cent 1N4007 diode, so I figure why not. the cause of my 2553 marshall silver jubilee redplating was a leaking bias diode. Had I changed it when I did the recap a few years prior, I would have avoided the issue.

I’ve seen this too where bad caps act as a short on startup damaging the bias diode. Typically some circuits use a 4003 or 4004 diode but they should be a 4007 to account for the momentary short circuit on startup. I also recommend changing any bias diode to a 1N4007 or equivalent.