Hello,
A friend dropped off an amp head for me. This is the model with an ECC83 in phase shifter. The amp dates from 1973-74.
The fuse blows. The power supply capacitors are original. An EL34 is rinsed. The transformers are not cut, The zeners are heated well.
After research, in addition to changing the 100uF 450V and 20uF 450v capacitors, I was thinking of changing the diodes and resistors of the power supply (low voltage and high).
zener by 5W, diodes on the el34 anodes by THT (4000v) + capacitors (MLCC, Through-hole, 1.5nF, 2kV dc, ±10%, dielectric: X7R)
I am giving you 2 diagrams because the one that interests us is illegible while the other is close (2475-130) and... more readable!
If you know these amps and/or if I make a mistake (with the 5W zener instead of 1W for example), please tell me.
A friend dropped off an amp head for me. This is the model with an ECC83 in phase shifter. The amp dates from 1973-74.
The fuse blows. The power supply capacitors are original. An EL34 is rinsed. The transformers are not cut, The zeners are heated well.
After research, in addition to changing the 100uF 450V and 20uF 450v capacitors, I was thinking of changing the diodes and resistors of the power supply (low voltage and high).
zener by 5W, diodes on the el34 anodes by THT (4000v) + capacitors (MLCC, Through-hole, 1.5nF, 2kV dc, ±10%, dielectric: X7R)
I am giving you 2 diagrams because the one that interests us is illegible while the other is close (2475-130) and... more readable!
If you know these amps and/or if I make a mistake (with the 5W zener instead of 1W for example), please tell me.
Attachments
The diodes are easy to test with a meter, so no need to replace unless bad. Have you measured resistance to ground of the plate supply of the output tubes?
Hello, I measured the primary of the OT, 300-400 ohms from the midpoint, each part. The resistance between pin 3 of the sockets (without EL34) and ground is around 600K ohms.
I finished replacing the power supply capacitors. How is the bias adjusted ? what voltage should be applied to the 330K resistors ? or what voltage should be measured on the 10 ohm resistor ?
