Marshall Super Lead RI Oscillation trouble

[sunshine_bassman]

I switched out the R28 47k bias resistor for a 33k to get the amp biased in range. I was able to get proper readings on one side of the OT while checking bias, where I read 15.3ohms between center tap and brown primary, as well as -1.2vdc. My problem is that when checking these readings on the red primary, I got +25vdc between center tap and primary. When I pulled the phase inverter it read properly at -1.2vdc. What went wrong here?

[Helmholtz]

Connecting the meter lead to the red primary wire causes the amp to oscillate and gives wrong idle reading. Happens often. Pulling the PI tube disrupts the FB loop, stops the oscillation and allows correct idle current reading.

[sunshine_bassman]

So nothing to see here?

[Helmholtz]

So nothing to see here?

What do you mean?

[sunshine_bassman]

Sorry, I meant “nothing needs to be corrected there?”

[Helmholtz]

Sorry, I meant “nothing needs to be corrected there?”

No indication of anything being wrong. Pulling the PI tube before connecting the meter to the OT is a recommended procedure.

[J M Fahey]

Like I just posted on another thread: what is the actual problem you are trying to solve?
What was the owner´s complaint?