GW Instek 2030D Dual Rail PSU Master Channel Voltage Maxed Problem

This PSU from Taiwan has a Master side voltage max out to 45V as soon as you turn the current sense control up and seems to be an issue for others on the Net. This unit seems an exact clone of the Tektronix PS280:

Tek_PS280-283_Service_Manual_Schematics.pdf

Suggestions for checking the control pots makes sense first as any bad pot here could switch the logic to the max out put.

It’s a nicely built unit and the front control board comes away easily after removing the pots knobs and the nut/washer.

The fault on mine was the 10k master voltage (and slave side value) pot had cracked from being loose, so pushed back which clean broke the bakelite board tracks, leaving the pot open circuit. This accounts for the behaviour as soon as the current sense (1k pots) is turned up so the green sense LED lights, the logic senses the voltage pot at maximum so switches the all 3 relays on in quick succession to give a maxed out voltage of 45V on the output. The odd thing is that working the slave side only goes to 30V maximum in Independent Mode, so it seems the master side should also – so not reach 45V but the max 30V voltage also. Maybe there’s a clue in the schematic..