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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: Do I put that resistor in the circuit to ground? Did you mean 7591's? posted by PeterI on March 13, 2007 at 10:32:22:
Yes, I meant 7591s... there are three preamp tubes that get heater current from the 7591 cathode current. There's a 600 Ohm resistor to ground from there, according to schematic - the 240 Ohm goes in parallel with that, cathode to ground. 244 in parallel with 600 is 171.5 Ohms, 33V across that is 192 Ohms, or 48 mA per tube. I'd also add a 10 Ohm resistor in series with EACH cathode to give a point to check current per tube. Would be nice if the original 7591s are still matched, but I'd check.
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Follow Ups
- Re: Do I put that resistor in the circuit to ground? Did you mean 7591's? - Tom Bavis 11:25:29 03/13/07 (2)
- Thanks again. - PeterI 14:35:24 03/13/07 (1)
- Any suggestions about upgrading this amp welcome (nt) - PeterI 21:05:41 03/13/07 (0)
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