• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Quest for Sweet Sound Hits Snag

Help needed - resistor/fuse burnout

Thanks for the previous input. I replaced my caps and used the variac since I had it hooked up any way. At about 80 volts input my power resistor started smoking. I replaced this also. I guess I shouldn't have been surprised since the old one was mostly cooked, but I thought it may have had to do with the filter capacitor. The rectifier tube is the 5AR4 with a dual can capacitor and a 100 ohm 10 watt resistor which then goes to the 6BQ5 Screen. Originally the cap was 40/80mfd 400vdc but in replacing I went with a 20/100mfd which I was told would be ok or maybe even better. The cap is a NOS electolytic - could this be the problem.

After the initial start up I shut it down and checked my wiring to make sure nothing was shorting out, and then cranked it up again. It didn't smoke this time. I only took it to about 80 plus volts (enough to get some sound out of the speakers) After a minute or 2 the 2 amp slo-blow fuse went. And I realized I have a problem.

What could cause this excessive current draw?

Once again I greatly appreciate your assistance on trouble shooting this.