Heathkit AA-1640 recap assorted questions

[abnormalcat]

Howdy,

I'm doing a recap on my Heathkit AA-1640 to bring it into the modern area and hopefully in service for many more years. As this is my first foray into doing this, I've run into some things and have some questions.

1. There are some low-voltage non-polar electrolytics on the amplifier boards that I should probably replace. (part 25-249 C209 for those following along in the manual/schematics) They're 250 uf at 4 volts. Those values don't seem to be available from Mouser or DigiKey or really anywhere. I'm assuming going wildly up in voltage to, say, 100v is inadvisable. What's the best practice for stringing capaitors up in parallel to get the right value?

2. There are a ton of disc caps everywhere. My homework notes say most should still be good, but there are some disc capacitors that go bad sooner and should be replaced. How do I tell which ones are more susceptible to this degredation and which ones I should leave in place? I bought the aa-1640 resoration kit from Hifiaudio and it included a ton of new film caps - If I don't have to replace them though I'd as soon rather not.

3. While I'm buried in this giant machine, anything else I should be on the lookout for?

Thanks!

 

[rickl]

#1: I don't know where these BP caps are used but I'd try 220uF/16v or 25v. Muse es nichocon UES. A lot of times these are used to decouple sections.

There is a lot of passion on caps so feel free to search for bipolar on AK.

Does the amp work? If not, get it working first, use DBT, ... You might enjoy it with original caps.

Then recap if needed. I might focus on protection and power supply sections.

Posting pics and schematic bits always helps.

 

[hamrules]

You could get a 250uf axial non-polar @ parts express if you could fit that in.

 

[abnormalcat]

#1: I don't know where these BP caps are used but I'd try 220uF/16v or 25v. Muse es nichocon UES. A lot of times these are used to decouple sections.

There is a lot of passion on caps so feel free to search for bipolar on AK.

Does the amp work? If not, get it working first, use DBT, ... You might enjoy it with original caps.

Then recap if needed. I might focus on protection and power supply sections.

Posting pics and schematic bits always helps.

Howdy, thanks for the reply. You think 220uf is close enough or do I piggyback a 33uf on top of that? I'll definitely be doing more sorting through old posts and theads.

It works! Pretty sure it was factory-built by Heathkit and the guy I bought it from said it sat in a closet for at least the past 20ish years. I probably didn't Absolutely need to recap it, but I did find a resistor that got a bit warm so this wasn't a total waste of time.

Attached (hopefully) is a schematic pic and the 4v cap in question. Plus some pics of the inside.

 

[abnormalcat]

You could get a 250uf axial non-polar @ parts express if you could fit that in.

There's plenty of space, I can only find 100v 250ufs on parts express though. Could be wrong but other threads have said best practice is to not go much past 2x the voltage rating?

 

[llwhtt]

Going with a 220uF will only affect the very low bass, you may not even notice. Nichicon ES 220uf @6.3V should work fine. You might even try a 330uF.

Craig

 

[lrb1951]

I would go higher in capacitance. I think I used 330 uf 16v Nichicons when I recapped the AA-1640 I have. I used 330uf to replace the 250 uf capacitors in all my AR-1515s and AA-1515s that I recapped. They all play and sound just fine. Those Nichicons are still available at Mouser.

Larry

 

[lrb1951]

The radial capacitors will work just fine, no sense in paying extra for the axial type which may not be available. Just solder on the extra wire if you need to.

Larry

 

[abnormalcat]

I would go higher in capacitance. I think I used 330 uf 16v Nichicons when I recapped the AA-1640 I have. I used 330uf to replace the 250 uf capacitors in all my AR-1515s and AA-1515s that I recapped. They all play and sound just fine. Those Nichicons are still available at Mouser.

Larry

Thank you! I'll do just that

 

[loudnoises]

These days all the caps I buy seem to end up testing on the low end. If the original was 250uf 20% and you put in a 220uf that's 10% low you've already hit the bottom (200uf) of the acceptable range. I would not start off that much lower.

250uF 100V Electrolytic Non-Polarized Crossover Capacitor

250uF 100V Electrolytic Non-Polarized Crossover CapacitorElectrolytic non-polarized (bi-polar) capacitors are perfect low-cost solutions for use in passive speaker crossovers. These capacitors feature axial leads, a 5% dissipation factor, and are rated at a 100 VDC working voltage which equates...

www.parts-express.com

You can sub in a np for a polar, just not the other way around. Np=bipolar. A polarized radial cap will not work here.

 

[lrb1951]

Don't worry about the ceramic disc caps or the mylar caps, they are not known to go bad. No electrolyte to cause problems in them.

Larry

 

[abnormalcat]

Howdy all, thanks for your wisdom and advice. I stuck in some 330uf 16v nonpolar Nichicons and she powers up like a beaut. Sounds good too! Final pics will have to wait until I replace the outputs and put the whole thing back together, but it's a massive relief that she powers on and plays well.