KSGER T12 - Help me identify this wire - Page 1
Forum section: electronics / general

author: twang817
author_rank: Newbie
timestamp: November 22, 2023, 06:36:57 am
content: I bought a KSGER T12 3.1S several years ago for a project; but, never got around to using it.I knew that I wanted to ground the case and possibly snip off a corner of the heatsink that sits over the primary. So, I finally opened it up today and noticed that I have an addition green wire that's soldered from the JST that supplies power to the control board. I haven't seen this in other pictures online and wanted to ask what this was:

author: floobydust
author_rank: Super Contributor
timestamp: November 22, 2023, 08:24:39 pm
content: Your oddball controller board looks like a lemon - U5 is an LDO that doesn't have enough heatsinking?The old controller boards mistake is not enough copper pour so the IC overheats. Adding the wire (if soldered to the IC tab) would help with that, acting as a heatsink.Otherwise it looks like a bodge or there is a mistake with the PCB traces. I could be wrong not able to see what extra parts are on the board other side.So I would check if it's running crazy hot and that is the real issue that the bodge wrongly tries to fix.Power supply V2.04It's easier to put Kapton tape under the heatsink fin on the +HVDC trace. Taking the heatsink off is a lot of work.Power supply V2.05 fixes moved the offending trace over and added a pad for PE GND.

author: xfint34
author_rank: Contributor
timestamp: November 23, 2023, 03:30:20 pm
content: Looks to me like the diode from 24v into the 3.3v regulator is removed. The green wire is powering the regulator instead. I wonder if the green wire comes from that DPAK on the bottom right. Under the cow silkscreen.I think those pads not populated on stock 2.04 power boards? On some schematics I've seen it's referred to as the "mystery" DPAK. Judging by the left over resin, it looks to me like it was put on afterwards on your board. I wonder it that's another regulator that steps down from 24v to some intermediate voltage. Then to the 3.3v regulator.

author: floobydust
author_rank: Super Contributor
timestamp: November 24, 2023, 02:09:14 am
content: They've struggled with making a decent 3.3V rail from the 24V rail, that doesn't overheat or be too noisy for the thermocouple amp.Lately it's a 7808 and AM1117-3.3 combo. It was the HW5026 buck-converter but they were out of stock due to shortages.Mystery DPAK I thought has a trace to nothing, and the pinout didn't make sense either. I wonder what IC is it on OP's PSU and if that is where the green wire is supposed to connect to.

author: twang817
author_rank: Newbie
timestamp: November 25, 2023, 04:43:12 am
content: Interesting... thanks for the info.The basics of the iron work -- I've used it the past couple of days and didn't notice anything wrong with it. I'll make sure to keep an eye on and and see if it gets really hot.Is the unit dangerous? Would submitting more pictures help?

author: floobydust
author_rank: Super Contributor
timestamp: November 25, 2023, 05:58:40 pm
content: The PSU has no safety approvals like all chgeap gear from china and the transformer could be wound properly (safely) or not.Just check continuity between power cord PE GND and the tip.Otherwise the tip can have stray AC voltage and damage semi's. You can measure ACV between PE GND and the tip when the unit is on.