MCH-305D-II bench power supply can't change current on one channel

[cozycactus]

someone have advice on repairing this bench power supply?
right channgel 0-30v works good, but left one i can only change voltage, but when i short the +- outputs i have constant current of approximately 4.5A that i can't change with current potentiometers.

[teatime]

The current potentiometer maybe aged.
you can try to replace a new one.

[teatime]

Attached please find the schematic of this power supply.

[cozycactus]

thanks. its linear psu , not spsu as in your schematic

[m k]

It can still be a pot problem.
There can also be multiple pots in series.

https://www.eevblog.com/forum/repair/looking-for-the-schematic-of-a-dual-30v-5a-psu-clone/