Re: Dynaco question, popping noise, can cap,PAS resistors

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In Reply to: Re: Dynaco question, popping noise, can cap,PAS resistors posted by airtime on July 28, 2002 at 09:24:58:

AT,
Change the electrolytics, in the bias supply, if the new filter board doesn't have this provision. Put in new diode(s) into the bias circuit, too. Watch all polarities.
Check the resistance of those 15.6 ohm resistors tied to the cathode of the EL34's. They need to be spot-on, if your bias readings are to be accurate. If they are off, replace them with precise 15 ohm, 5 watt resistors, which have as high temp rating (85C with 105C being better). Darn area near the power tubes gets hot---so stability of components is kinda essential.
If you go to 15 ohm resistors---your new bias reading will be 1.50 volts (as stating in a thread, below), for the EL34 tube. But, measure the resistance of the 15 ohm, 5 watt resistor BEFORE replacing the OEM one.
If it's value is 14.5 ohms---then, your bias point will be 1.45 volts. Or if it's 15.3 ohms---1.53 volts, etc.
You may be able to get 1% 5 watt resistors in 10 ohm increments. If you choose 10 ohms---then 1.00 volts is the bias measurement.
I'd replace those 1K ohm and also the 270 k-ohm resistors (around the bias read points 6 & 21, on the schematic) with 1% new resistors. They are a part of the bias circuit and needed to maintain stable bias, as Charles stated.
[my opinion] Actually, the whole mess above, is my opinion---but I'd slowly form the new board and the new bias supply electrolytic caps. The caps seem to last longer, that way. It would be nice if the new board could be covered with a metal top---in case one cap fails and spills its guts.

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Follow Ups Full Thread

Topic - Dynaco question, popping noise, can cap,PAS resistors - airtime 05:44:23 07/28/02 (6)

Re: Dynaco question, popping noise, can cap,PAS resistors - Jim Carlon 13:00:05 07/28/02 (0)

Re: I think you got some good suggestions below - navman 12:16:42 07/28/02 (0)

Re: popping noise - Ron Oehlert 10:02:30 07/28/02 (0)

Re: Dynaco question, popping noise, can cap,PAS resistors - Sector-7G 09:15:55 07/28/02 (2)

Re: Dynaco question, popping noise, can cap,PAS resistors - airtime 09:24:58 07/28/02 (1)

Re: Dynaco question, popping noise, can cap,PAS resistors - steven oda 10:01:03 07/28/02 (0)

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Re: Dynaco question, popping noise, can cap,PAS resistors - steven oda 10:01:03 07/28/02 (0)

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