Basic Electronics Help

[firgela]

I'm attempting to repair a Dynaco SCA-80 stereo amp I've had for awhile now. It developed a hum and I suspect the power caps.

This is how it looks on the parts list, C11 being a multi-cap:

C11 700?f@75v
700?f@60v
800?f@20v

Do I simply add the ratings? Would the cap listed here be the one I need? http://www.allelectronics.com/cgi-bin/c ... type=store

The tech at the studio who is fostering me through this is always busy, so I see him like once a month. Therefore, I turn to you guys for my infantile questions in this matter. A humble preemptive THANK YOU. -Danny

[Rodgre]

No. i think you can take three caps, of the individual values and use those, with a common connector. Am I right in assuming that this cap has four legs? One is common, and the other three are individual taps, so it's essentially three caps with the m all connected at one end.

I could be totally wrong, but that's what I would assume without seeing it.

Roger

[jerrymac]

and just to add a little to roger's post: sometimes if the multi cap is in a metal can, the exterior of the metal can is the common of all the caps inside the metal can.

-jerry

[firgela]

I don't have the amp here at home, but based on memory and looking at the schematic you are right about the 4 legs. The schematic shows three "voltage test points" on the cap which I assume are the legs.

i think you can take three caps, of the individual values and use those, with a common connector.

So I'd mount these on a pcb to replace the can capacitor?

[Randy]

Rodgre is right-- a multicap is basically a can that holds a number of different capacitors. It usually has a single lead for the common ground and the positive leads coming out of one end. The each lead has a different value and is usually color coded. The can usually shows what color goes to what value.

If you cannot get a multicap (or can) that matches the current one, you could always find three capacitors and hook them up where the can's leads went to. So for instance, if the can says:

yellow-700uf@75v
blue-700uf@60v
red-800uf@20v

you could get three capacitors at those values and find out where each color-coded connector goes to and solder one end of the corresponding capacitor to that point and the other end to ground. If the multicap has polarized caps (do they ever?), make sure you use polarized caps as replacements and make sure that you have positive side of the cap hooked to the positive side of the signal and the negative side of the cap to ground. Also, it doesn't hurt to get caps with a higher voltage rating.

Here are a couple of places that carry capacitor cans:

http://www.triodeelectronics.com
http://www.tubesandmore.com

[firgela]

I don't have the amp here at home, but based on memory and looking at the schematic you are right about the 4 legs. The schematic shows three "voltage test points" on the cap which I assume are the legs.

i think you can take three caps, of the individual values and use those, with a common connector.

So I'd mount these on a pcb to replace the can capacitor?

Just a huge thanks to everyone for pointing me in the right direction. And a bump here for one more.....question

So I'd mount these on a pcb to replace the can capacitor?

[aurelialuz]

So I'd mount these on a pcb to replace the can capacitor?

not totally sure what you mean, but if i understand you correctly, you can usually get all three in place of the can. just stand them on one end on the board, in a little cluster, and bring the top leg of each cap down to the board and solder up.

alex

[Scodiddly]

Sometimes antique radio restoration guys will empty out the can and put the new caps inside - newer caps are a lot smaller.

The multi-caps were a cost-saving thing. It's easier/cheaper to build three high-voltage caps together than separately.

[The Scum]

I just got a flier from Antique Audio supply, and they had some multicaps listed.

Check http://www.tubesandmore.com/ . It'll help if you know the original manufacturer of the cap.

Byron Jacquot