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In Reply to: RE: This might be close. posted by Tre' on January 16, 2022 at 06:32:53
I will replace the 220k with some 100k.
As for the zener diode string from what I have read this will be in series with the center tap and not the b+ ?
I also have a problem with the negative bias supply the selenium stack I replaced with a silicon diode I was to inexperienced at the time to account for the voltage or less of a voltage drop and now it will only let me adjust down to -32 which gives me about 18ma on each of the output tubes. Would it be OK to put a zener in the bias supply to shed some volts?
Thanks for all the help!
Follow Ups:
Rather than "regulating" the bias supply, just change a resistor or two to get the voltage into range. Better to have the bias, plate and screen voltages change together with line voltage - if bias voltage is truly fixed, dissipation and operating point vary with supply voltage. They'll "track" if all are left unregulated (regulate screen and grid voltages and it will be even better, but that gets complicated...)
Ok I played with the divider in the bias supply and now I'm able to get -17 output tubes are drawing about 35 ma I don't know how accurate this old weston 911 is though.
Thanks for all the help guys especially Tom who has helped me with many amps from magavox to my heathkit aa-81 mono blocks.
I now suspect that the 10watt 560 ohm resistor I put in front of the input filter is really making some heat so should I find some 1k or 1.2k 10 watters and double up?
Ok nevermind about the paralleled resistors now that the output tubes are drawing proper current there's no need for the dropping resistor to be in there.
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