GW/Instek GPC-3020 power supply

Intro #

The GPC-3020 power supply is nearly identical to the Tektronix PS280/283, one being a rebrand of the other. This is fortunate because, while GW/Instek rarely provide service manuals or schematics for any of their equipment, there is a publicly available copy of the PS280/283 service manual.

front panel comparison

Differences with the PS280/283 #

Circuits are split slightly differently across the multiple PCBs
the layouts and wiring are different
the connector pinouts cannot be trusted
the voltage/current tracking circuit is quite different
probably others

Voltage/current tracking circuit #

I suspected my unit (and made a YT video) to have issues in this area and I quickly realized I would not be able to use this part of the Tektronix schematics. Its purpose is the same:

Activate the proper relays according to the front panel switches (normal/tracking, series/parallel)
Route voltage and current feedback according to same
“mute” outputs during mode changes

Traced schematics #

Here’s the result of a few hours work (PDF version): V/C and tracking circuit U501 is central, generating a short pulse that disables master and slave outputs via U502 and Q502 respectively. The output terminal PCB, bottom left, is also wired differently from the PS280.