Hi JS_NY1,
Welcome to the forum. If that's a linear power supply (I didn't see much with that model number), it sounds like the power transistor on that stuck channel is shorted. Remove it from the circuit and check. If it is shorted, then replace with a similar working transistor. If not, then do comparisons between the good and bad channels.
Although schematics can be helpful, you have the benefit of a working example as reference. You'll probably find the culprit with a little sleuthing.