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Questions about tubes and gear that glows. FAQ

Thank you! And cap questions?

Jonesy, first of all I want to express my admiration for your knowledge & my appreciation for your assistance. I took a couple of days off from the Big Cary, but tomorrow, I am taking the bottom back off & checking the 540 diode & the resistance of the bias pots as you suggested.

& then, after buttering you up, I was wanting to ask you a couple of more questions regarding caps.

But first: after the Bigg Cary went down I got the Little Cary out of mothballs. Right off the bat a rectifier tube went "fizz-bang!" & after I changed a tube I wound up with about a channel & a half (verified with pink noise & sound pressure meter), & after that I did a few sweaty hours of some completely retarded trouble shooting (to no avail), at which point I came back to it with a logical approach & fixed the 1.5 channel issue with a couple of spare 6SL7s I had in my "spare tube box."

Now the thing is, back in '99, when I had to send one of my ARCs back to Mn. because I set it on fire, I brought the little Cary out of retirement to fill in. At that time, I bought (from Cary) a DIY outboard (4 each 560 uf 400V caps) "cap bank" & umbilical cord to give the Cary some more pop. A couple of years later, I replaced my ARCs with my present day Big Cary, but, I got instructions & bought parts to hook "the cap bank" up into the Big Cary.

I am leery about everything right now, as as much as I'd like to add the dynamic extra capacitance back to the Little Cary, I am afraid that if one of those large caps in "the cap bank" went bad & was what brought the big guy down, I don't want to smoke the little one the same way. I realize that I could set the Big Cary back up WITHOUT the cap bank to see if that resolves everything (& I may do that), but it seems like it would be easier if I knew how to check those large caps.

Referring back to a previous reply you gave me, I am relatively sure that the caps were discharged when I put my multimeter on them, & regardless, the multimeter seems to have survived.

My first question is: is there something I need to check large caps with that I could pick up at Lowes?

Secondly: earlier you mentioned that electrolytic caps have a finite life span (which I wasn't aware of) of around 20 years. But does that include just sitting a circuit being unused?


7-5-2019 "Our army manned the air, it rammed the ramparts, it took over the airports, it did everything it had to do, and at Fort McHenry, under the rockets' red glare, it had nothing but victory."

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