Re-capping my '69 Sunn Sentura II and '68 Traynor Bassmaster soon. Have questions.

[Boy Howdy]

Hi all.

I'm no amp guru, but I have replaced electrolytics before. Everything will go swimmingly I'm sure (With the amp plugged in and and the power on, I'll bleed off the current through my finger while standing in the shallow end of the pool. That's the rule, right? Safety first.). No, seriously, I know all the precautions and will do the job safely.

Questions:

When I bought my most recent Sunn it had already been re-capped with a vintage type can. I plan to use individual caps instead. Should the caps be wired in series or parallel? I can't see inside the cap can to know. I looked at the schematic the other day, but I'm not real great with schems, so I wanted to confirm with you guys.

Also, the guy when he recapped the Sunn replaced all the electrolytic caps in the amp. Is it really necessary/desirable to replace the small non-power supply caps too?

Thanks. But don't go away. I will have some other questions once I get all the parts (the Traynor has other issues).

[Mars Amp Repair]

Hello,
Most cap-cans are 2, 3, or 4 internal capacitors with one common node...the can is ususally the negative connection of each cap.
So as they stand, they are neither in parallel or series...just separate caps with one common (usually the negative) connection. If all caps are supposed to go to ground, the cap-can case tabs are soldered to the chassis or connected to a ground point via wires.

Hope that helps. The info is ususally stamped into the side of the can. glen

[Boy Howdy]

reply

Yeah, that's a little confusing. Something tells me I need to take a closer look at the schematic. Or maybe I should just use cans. Not liking the idea of dealing with those solder globs though.

To whomever may be interested to know, I'll be offline until Monday.

[soundmasterg]

The problem with the cap cans is that they are not rated for the voltages that these amps have with today's wall voltages. The plate voltages in your amp are probably somewhere around 550v.

Use discrete caps connected in series, and make sure to use the 220k 1w resistors in parallel with each cap. You need at least a 500v rating at the third stage and at least a 600v rating at the first two stages, so just use some 350v caps in series for a 700v rating and you're set. Leave the cap can in place for cosmetics but disconnect it from the circuit.

Greg

[Boy Howdy]

Thanks, Greg.

Looks good from here.