What To Do When A Vintage MultiCap Gets Soft - - -?

[beatpoet]

I'm working on an old RCA radio. I'm pretty sure the multicap is deteriorating, it's getting some nice hum at the output.

I've yet to look at the trimmers, but:

What can I do to fix this thing? Large vintage & working multicaps aren't readily available anymore (are they?)

I thought about adding a few uF between the multicap and ground to bolster the thing up for a while.

How about additional caps in parallel with each tap? The owner of the amplifier said I can do some minimally invasive & discreet adding of modern parts if I must.

...Sorry, I couldn't find a schem. for all of you schematic fiends...

 

[EZ81]

Can you open the can, remove the innards and put in single new caps (which are way smaller than old parts, so they should fit)? I did this in a vintage radio and there was plenty space inside the can caps.

;Matthias

 

[thermionic]

[quote author="beatpoet"] Large vintage & working multicaps aren't readily available anymore (are they?)

[/quote]

They are here - I bought some a few years back. I was told they bought the Mallory jigs to make them.

Don't try bypassing worn out caps with new ones whatever you do - not a good move!

If you can't get the right multi-section cap, the last resort is to try and drill out the old caps and insert modern caps in the can - it's fiddly, but I've seen it done.

Justin

edit - Matthias beat me to it!

 

[emrr]

usually just have to get real creative with doing hang-ups elsewhere; add standoff's to existing screwholes, re-route wiring, whatever. Filter multisection cap with resistors between every lug are the worst bitch and require the most creativity. Cathode bypass is very easy. You can parallel more capacitance if they are losing value, but you never know if they're headed for a short related failure in the future. Better to outright replace.

 

[NewYorkDave]

Don't touch those trimmers if you don't have an RF signal generator and the knowledge of how to align a receiver.

 

[CJ]

is this what you had in mind?

www.tubesandmore.com

 

[sodderboy]

tubesandmore.com :thumb: :thumb:

if they do not have the exact configuration, what I have done is to take the can out of circuit but leave it physically installed, and add the necessary radials underneath to do the work.

I have done the empty the can thang before, but it entails exposure to hazardous chemicals so wear gloves and work on newspaper if you HAVE to do it that way. I pass if anyone wants me to do that now.
Mike

 

[beatpoet]

I couldn't find the exact cap... I don't think I'm going to be disassembling one of those things either.

Or maybe I could use cap oil to fry up a big batch of selenium chips (crunchy snack) :shock:

I'm guessing the guy won't mind if the cap non-original. Probably just doesn't want it to look cobbled together, or 'too' new.

C-ET10-10 is the closest there.

This guy has been good for the recent string of amps that I've had to fix:

http://store.triodestore.com/

but alas, no multi-caps.

 

[emrr]

The exact cap; almost always the problem. Followed by the exact size. If he wants it work....

 

[Rob Flinn]

Beat

As said before the old boy radio restorers retro fit new caps inside the can of the old cap.

 

[CJ]

If it has a cardboard cover, you can put that over the replacement cap to fool them. This gets done on olf fenders sometimes to preserve the value, un be knownst to the un wary.

 

[David Kulka]

As an antique radio/TV enthusiast, I can tell you that this has been addressed many, many times on one of my favorite sites. try a search there...

http://antiqueradios.com/forums/index.php?sid=1d5cf08165ad8dd1671d341ce603ec1c

 

[skipwave]

[quote author="beatpoet"]This guy has been good for the recent string of amps that I've had to fix:

http://store.triodestore.com/

but alas, no multi-caps.[/quote]

Huh?

http://store.triodestore.com/twisel.html