(This is also posted on Audiokarma)
I'm starting a new thread so I don't hijack another thread and my symptoms might be bit different.
I recently acquired a nice ST-70, plugged it in and it worked well. I wanted to 'bring it up to date,' replacing the rectifier, electrolytic caps, input jacks and bias test jacks. Did that and now its blowing fuses and bias is 0 volts.
I've gone back and rechecked solder joints, checked resistor values in the bias circuit path, etc. Checked voltages at several points along the path:
input voltage: 120V AC
filament voltage: 6.85 V AC
AC side of new 1N007 diode: 50 V AC
DC side: 33 V DC
input to bias pots: 13.3 V DC
at eyelets 6 & 21: ~ 7 V DC
at eyelets 22,23 1 & 2: -.03 to -.20 V DC
at pin 8 of the EL-34s: 0 V DC
B+ BTW is ~495 V DC
Measurements were made with both qa VTVM and a DVM and are fairly close to each other.
Inputs were shorted during measurements.
I'm stuck. Any ideas?
Ray.
I'm starting a new thread so I don't hijack another thread and my symptoms might be bit different.
I recently acquired a nice ST-70, plugged it in and it worked well. I wanted to 'bring it up to date,' replacing the rectifier, electrolytic caps, input jacks and bias test jacks. Did that and now its blowing fuses and bias is 0 volts.
I've gone back and rechecked solder joints, checked resistor values in the bias circuit path, etc. Checked voltages at several points along the path:
input voltage: 120V AC
filament voltage: 6.85 V AC
AC side of new 1N007 diode: 50 V AC
DC side: 33 V DC
input to bias pots: 13.3 V DC
at eyelets 6 & 21: ~ 7 V DC
at eyelets 22,23 1 & 2: -.03 to -.20 V DC
at pin 8 of the EL-34s: 0 V DC
B+ BTW is ~495 V DC
Measurements were made with both qa VTVM and a DVM and are fairly close to each other.
Inputs were shorted during measurements.
I'm stuck. Any ideas?
Ray.