• 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.

Copland CTA405A - faulty resistor

Hello, I have a problem, the device works normally on the two channels, but when I measured the bias of the KT120
according to Copland procedure, on the first 3 valves it was approximately 0.47V, on the last right V203 valve it was approximately 5V,

clearly the trimmer does not have this range. I swapped two valves, but the problem remains on V203.

I tried to measure the impedance of the resistors in front of the trimmers of each valve with the digital multimeter, on three resistors R120-R119-R220 it was 10 Ohm, on the fourth R219 (always in correspondence with the V203 valve), the message " OL" value too large.

So is the resistor faulty? or could it depend on other components?

Can anyone tell me what type of resistance/impedance/tolerance is the R219? The colors on the resistor are not very clear.
Does anyone have schematics of the Copland 405A?

Thank you