Need some help recapping a C28 power supply

Although there does not appear to be anything wrong with the cap cans already in my c28 every post I have read at this and other forums say that at 40yrs old they are just a disaster waiting to happen. That scares the c**p out of me. I haven't had any problems finding caps at or very near the values that I need but I am entirely at a loss as to which properties best suit my needs. By this I'm referring to "high ripple current, high temp, low impedance, general purpose, etc". I have no idea what that means, my knowledge of electricity extends no further than I know you can't see it and that it will shock you. Any little bit of guidance would be helpful.

Thanks

Fueler said:

Although there does not appear to be anything wrong with the cap cans already in my c28 every post I have read at this and other forums say that at 40yrs old they are just a disaster waiting to happen. That scares the c**p out of me. I haven't had any problems finding caps at or very near the values that I need but I am entirely at a loss as to which properties best suit my needs. By this I'm referring to "high ripple current, high temp, low impedance, general purpose, etc". I have no idea what that means, my knowledge of electricity extends no further than I know you can't see it and that it will shock you. Any little bit of guidance would be helpful.

Thanks

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The factory probably has replacements.

The factory DOES NOT have replacements.

The key to replacement caps for the C28 power supply is the diameter of the replacement devices. The original can caps are no longer available.

Some folks will go to the trouble and expense of replacing the originals using custom-built cans. Check Hayseed Hamfest as a source - yes, that's right exactly as I typed it!

For the 2 C28s I've redone, I used individual caps for each of the sections of the can caps. Here' the trick is to find caps of the right values and voltages but are small enough in diameter to fit under the chassis. This will take some 'finesse' in dressing them and then fabricating a connection strip that allow you to route the connections back to where they need to be.

For the can caps, you can use regular (read: not boutique brand$ of caps) electrolytics that are small enough in diameter.

If this is your first restoration, the C28 project is a Big Mac Meal but Supersized. This not going to be a drop-in of exact replacement components. Also, see all the threads here about the grounding and drain wire rework needed to bring a C28 back into original condition. If doubtful about all this, I'd suggest it take a trip to Audio Classics or Terry DeWick.

Cheers,

David

bktheking said:

The factory DOES NOT have replacements.

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Not saying you're wrong, but, last year, I spent weeks considering alternatives for the canister caps on my c-24. I called the factory & was told not available.

Couple of weeks later, I needed to replace a transistor, so I called the factory again. Talked to a rep who found the transistor. Since I had her on the line, I asked about the cans. She said she'd call me back. Thirty minutes later I had 'em both on order: One was around $8.00, the other $14.00. Finding the right part numbers was the issue.

There are a numbet of how-to sources on doing a work-around.

Yes , other caps are available on eBay for different pre's but not the c28

I ended up restuffing all 4 caps, jbwelded the cans back together and heat shrank them after. No mess underneath, looks factory, retained the rivets as well. It's a delicate process to remove the caps but it can be done.

That is a sweet looking C-28. :yes:

You know it! Lamps came in today, you'll have it back very soon!