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AR 3a Capacitors


Shacky

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Now that I have a set of woofers I'm digging into my second AR 3a project. Plan to use Ohmite pots I picked up. Before I replace caps what are opinions from those in the know? Do these caps hold up? I was thinking the cans were oil can caps but the resto article says they are electrolitic inside cans. What does that mean?

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Hi Jim:

The blue capacitors are electrolytic; Sprague if I recall. They were made with an excellent hermetic seal and had a longer useful life than most brands. The tan box--the tweeter cap--contains an oil-impregnated paper capacitor, whose hermetic seal is shot by now. Have looked at many of them and most of the time, their capacitance remain in spec, but their dielectric loss and ESR both had increased significantly.

Capacitor recommendations, as you well know, draw more rapid and sharp responses than piranha going for food in a jungle pool. Good quality non-polar electrolytic work well. For me, polypropylene have worked well with a small series R in certain crossover locations. We pick them, because they will outlive my grandchildren! In the 70s Sprague and Cornell-Dublier made excellent hermetic seals; I have no forty-year encapsulation life test data on npes made in 2009 :huh: I am not sure if any mass production electronics today is made to last that long.

Cheers,

John

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I ordered Dayton 50 uF's for the mids and Dayton 1% 6 uF for the tweerers. Going to leave the 150 cans in place for woofers.

I didn't trust that silver can. Doesn't look as well sealed as the blue.

Any thoughts on bypass xcaps? I have some nice Russian Military PIO 0.047's that would if anything make for conversation pieces ; )

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Decided to go a bit rogue. Updating the binding posts. I filles the 3 original screw holes and drilled 2 the std 3/4" for so PE posts. I've always been a little suspect of those old wire connectors inside. This way all wires will get fresh ends and woofer/mid/tweeter will be permanently tied together.

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Now that I have a set of woofers I'm digging into my second AR 3a project. Plan to use Ohmite pots I picked up.

Hi Shacky

I'll be interested to see how you solve the problem of enclosing the Ohmites to keep the fiberglass out. I have a few of those myself and have been thinking about that. Is heat really a problem? I had thought maybe a stainless steel measuring cup might work but some members are concerned about heat dissipation. Will be interested to see what you come up with.

Those new binding posts are nice.

Kent

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Hi Shacky

I'll be interested to see how you solve the problem of enclosing the Ohmites to keep the fiberglass out. I have a few of those myself and have been thinking about that. Is heat really a problem? I had thought maybe a stainless steel measuring cup might work but some members are concerned about heat dissipation. Will be interested to see what you come up with.

Those new binding posts are nice.

Kent

That is the perennial 64K question!

I used some landscaping cloth in past. First time it got caught up in the swepper. Then I thought of putting some dowels in there to raise it off the Ohmites. Another pair of 3's I tried using some cheap tupperware I cut and wrapped around them. It's worked pretty well.

I went to hardware store yesterday and challenged the guys for a solution. One was computer grommets. They aren't tall enough and not sure one would cover both or two would fit.

So one of the guys looked at some child door knob protectors. They split in have to go around door knob. I'm going to give them a try but they look like it will be tought o get them in place. Plus I'll need to sand down the back edge to fit them around the Ohmites. Will give it the college try.

I really just got fed up with the little screw caps on my AR's and decided to go modern with the binding posts. Might degreade value but I doubt I'll be selling these any time soon - at least I hopw not.

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