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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: RE: my bias is running away on one side even with the bias backed all the way off on that side! posted by Jonesy on July 24, 2020 at 17:04:11:
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?
Thaks!
Matt
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Follow Ups
- Thank you! And cap questions? - immatthewj 22:03:52 07/25/20 (21)
- RE: Thank you! And cap questions? - Jonesy 23:42:26 07/25/20 (20)
- RE: Thank you! And cap questions? - immatthewj 17:12:33 07/26/20 (19)
- RE: Thank you! And cap questions? - immatthewj 17:24:29 07/26/20 (18)
- RE: Thank you! And cap questions? - immatthewj 17:44:30 07/26/20 (17)
- RE: Thank you! And cap questions? - Jonesy 18:53:48 07/26/20 (16)
- RE: Thank you! And cap questions? - immatthewj 11:04:37 07/27/20 (15)
- RE: Thank you! And cap questions? - Jonesy 11:44:28 07/27/20 (14)
- RE: Thank you! And cap questions? - immatthewj 14:24:26 07/27/20 (13)
- RE: Thank you! And cap questions? - Jonesy 09:33:47 07/28/20 (11)
- RE: Thank you! And cap questions? - immatthewj 11:48:52 07/28/20 (10)
- ... also a reminder bias is set with no signal. It goes up and down once signal applied. (nt) - Jonesy 15:01:40 07/28/20 (8)
- RE: ... also a reminder bias is set with no signal. It goes up and down once signal applied. (nt) - immatthewj 20:25:26 07/28/20 (7)
- RE: ... also a reminder bias is set with no signal. It goes up and down once signal applied. (nt) - Jonesy 21:27:18 07/28/20 (6)
- RE: ... also a reminder bias is set with no signal. It goes up and down once signal applied. (nt) - immatthewj 12:50:31 07/29/20 (5)
- Economic "in circuit" capacitor meter - Jonesy 14:50:59 07/29/20 (4)
- RE: Economic "in circuit" capacitor meter - immatthewj 14:59:45 07/29/20 (3)
- RE: Economic "in circuit" capacitor meter - Jonesy 15:11:12 07/29/20 (2)
- RE: Economic "in circuit" capacitor meter - immatthewj 15:24:56 07/29/20 (1)
- RE: Economic "in circuit" capacitor meter - immatthewj 16:26:12 08/05/20 (0)
- RE: Thank you! And cap questions? - Jonesy 14:44:08 07/28/20 (0)
- RE: Thank you! And cap questions? - Jonesy 14:54:19 07/27/20 (0)
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