Altec 1569A ? transformer prob?

Hello

first post, but longtime lurker... great source for Altec enthusiasts.

I have a pair of 1569A power amps that I use to drive the low end of my 4343's, in a bi-amp config for some years now. Absolutely happy with sound and performance, but one of them has now developed a nasty metallic sizzeling or crackling, while it still works. For a while it started after some hours of use, now it looks like it's getting permanent. Seems like it comes from the transformers (original 16433's, I believe), but not sure.

I'd really appreciate every input – if anyone has experienced this, also where else this might come from, and how to solve the prob. Thanks.

For Altec electronic parts Ira-Tec Pro mailto:[email protected] I think they can help for replacement parts.Or phone # (405)-324-5311

Hi Fangio, :welcome:

My first suspect would be one of the electrolytic caps, especially if they're originals. It could be almost any component, but the 'lytics have the shortest expected service life by far. Whatever it is, I would try to solve it before the failing component takes something else with it.

The xfmrs are very high quality, and the least likely suspect. The only Peerless xfmr I've known to fail was due to leaking/shorting 'lytics.

If you don't have the test equipment and/or experience to isolate it, blind replacement of all the 'lytic caps isn't a terrible expense to try before you splurge for a trip to the shop. Just match the values in both capacitance and voltage rating. You can exceed the rated voltage, but don't use a smaller value.

Hi moldyoldy ;)

really glad to see you're still active here. That’s the sort of expertise I had hoped for.

I'm glad I'm still active too...:)

Failing electrolytics can often be pinpointed with an ohm meter and capacitance test. (DON'T forget to discharge them first! 300+V can curl you hair and wipe out a meter set to ohms). With one side unhooked to open the circuit, a bad one will read some DCR and often will read a lower-than-label C value. An infrared thermometer can also pinpoint a bad one, as the short passes current, creating heat. If they're original, doing them all would be requisite in my book anyway, just for peace of mind. There are a few smaller ones "under the hood" too.

Added
Other than the cans, you can ID the remaining electrolytic caps by their polarity markings, both on the caps and the schematic. The film caps are non-polar, and less subject to shorts, being made with a "permanent" dielectric material.

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moldyoldy

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Moldy Oldy now that sounds like a Lansing Heritage moniker ;)

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Originally Posted by Altec Best

Moldy Oldy now that sounds like a Lansing Heritage moniker ;)

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Bingo! :) I for one still miss him over there.

Will check out your suggestions bfish, many thanks. Quite relieved to hear the transformers probably aren't the culprits. It would probably be a difficult task to find replacements.