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MelJon66 · 25th Apr 2020, 9:52 am

Thanks Chris, for taking so much time to help.

That's an excellent explanation and the fog clears a little. I now understand that when I was taking the voltages across the windings, even with the fuses pulled, there was still resistance in the circuit that meant I was not getting an off-loaded reading.

Later today I will remove the variac and connect a dual bench power supply in series which will give me up to 60Vdc. I was going to pull fuse FS3 and connect the +50V to pin 15 and the -ve to the scope ground. So, I will be applying +50V to the PSU output pin. That way the other PSU's will still get their +50V feed. Is that okay or should I be putting +65V on pin 12? That will require an additional 30V power supply so will be very cumbersome but is it the right way to do it?

I just want to check that I get a good steady trace before I take any further action.

Cheers
Mel

25th Apr 2020, 9:52 am	#18
MelJon66 Pentode Join Date: Apr 2020 Location: Somerset, UK. Posts: 174	Re: Cossor CDU150 rescue Thanks Chris, for taking so much time to help. That's an excellent explanation and the fog clears a little. I now understand that when I was taking the voltages across the windings, even with the fuses pulled, there was still resistance in the circuit that meant I was not getting an off-loaded reading. Later today I will remove the variac and connect a dual bench power supply in series which will give me up to 60Vdc. I was going to pull fuse FS3 and connect the +50V to pin 15 and the -ve to the scope ground. So, I will be applying +50V to the PSU output pin. That way the other PSU's will still get their +50V feed. Is that okay or should I be putting +65V on pin 12? That will require an additional 30V power supply so will be very cumbersome but is it the right way to do it? I just want to check that I get a good steady trace before I take any further action. Cheers Mel