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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?


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