In something this cheap, you will not find good service/repair docs.
I have these schematics, the one I fixed was an old B&K Precision 1670 or 1671. Sch does not include the ICL7106 panel meter portion.
Inside is a rat's nest of wiring and hodge podge of parts.
Like many of these Taiwan/china bench PSU clones, they blow up charging batteries.
If the output voltage ever goes around 7V above the setpoint, backfeed kills the pass transistor+driver, then the op-amp shorts and damages other parts.
The red Current-limit LED usually explodes across the room.
Switch off power or a power outage occurs with a battery connected, power comes back on and you have a bonfire happen. Kinda creepy.
Reverse-voltage also kills some models without a big diode there.
You have to add a few protection diodes to really fix the design, and the driver transistor needs heatsinking.
I would recheck the pass transistors, the red LED, and replace the dual 4558 op-amp or LM741's if that is what got used.
When making voltage measurements to troubleshoot, note that PSU output (+) is circuit common for all the control circuitry.
Use DMM (-) to PSU OUT (+) and voltage readings will make more sense. The entire control circuit floats with the PSU output (+).
In the same family of these re-labelled bench power supplies:
Manson EP-601, analog panel meters, 0-30VDC 2.5A
Manson EP-603, analog panel meters, 0-30VDC 2.5A, Aux 5V 12V 0.5A
Velleman PS-603, analog panel meters, 0-30VDC 3A, Aux 5V 12V 1A
Manson EP-611, LCD panel meters, 0-30VDC 2.5A
Manson EP-613, LCD panel meters, 0-30VDC 2.5A, Aux 5V 12V 0.5A
Velleman PS-613, LCD panel meters, 0-30VDC 3A, Aux 5V 12V 1A
Circuit Test PSA-2530D, LCD panel meters, 0-30VDC 2.5A, Aux 5V 12V 0.5A
Jaytech MP-3082, LCD panel meters, 0-30VDC 2.5A, Aux 5V 12V 0.5A
Manson EP-3050 ?, LCD panel meters, 0-30VDC 5A, Aux 5V 12V 1A
Dick Smith Q1760, analog panel meters, 0-30VDC 5A, Aux 5V 12V 1A
The 5A and 2.5A are the same design, just beefier pass-transistors. I also have schematics for the one's with a fan.
Mastech HY-3010D, HY3005 is a bit different circuit design, also missing protection diodes and blows up just as easily.
https://www.eevblog.com/forum/beginners/manson-ep-613-dc-power-supply-troubleshooting