Hantek hdp135v6 lab power supply - BAD Design that can kill you!

[psydaddy]

Got this Lab Power Supply a couple months ago, used a few times


Today when connecting it to the microscope, it started to buzzing and when i touch the leads i got shocked. Measured from + to earth and i got 170V, measured from - to earth, same value.
Connected a jumper from earth to - and it buzzed like it did with the microscope connected.
The microscope is working fine. no problem whatsoever.

I remember charging a lithium pack with it last time, not sure if this was the problem. But still, leaking 170V to earth potential doesn't sound right.
I'm not quite sure where stuff connects, the PCB is all black and traces are very hard to see.

Disconnected the Y capacitors, and still does the same. Not sure how it is leaking, it should be insulated from mains.

Anyone got this same problem?

[psydaddy]

Found the problem... Chinese stuff.
The heatsink is connected to the mains after the bridge rectifier. There's a 0r resistor that connects it.

I've removed "R91" (0R resistor), but have to replace 2 mosfets that got broken in the process.
There's a power mosfet (IRFP260N) that is connected to this heatsink, and started to arc. I believe this was the reason it started to leak AC to the output of the power supply.

I've injected DC by the AC line and i was able to short circuit to the output of the power supply, reading the same voltage with a voltage drop of the bridge rectifier on the power supply output.
When removing this power mosfet, the short disappeared.

I'll let you know if it works when i get it back to work again.

[psydaddy]

This is how it is connected.

[psydaddy]

I was able to fix it, and it is working just fine.
If you want to protect yourself against electrocution, i would recommend you to remove that resistor. Do it at your own risk.

[gerryc89]

I have the same psu acquired some days ago, the resistor isn't present anymore.
Gerry

[bagunceiro]

Thanks for this. I got a belt off of the heatsink while inside to replace the crappy rotary encoders it has. It was unplugged at the time so from the capacitors. I've removed that resistor and all is well - can't see what it was there for, booby trap  perhaps. ?

[bagunceiro]

By the way, replacement of the encoders solved the problem I had, which was that when clicking to enable or cycle them it would not infrequently bump the selected digit as well, not good when it jumps from 3.3 to 13.3V! I replaced them with ordinary KY-040 devices. However, the coding is reversed so to avoid the confusion of having to remember to turn anti-clockwise to increase the value it is also necessary to bodge the board to invert it back.

[AntMAN]

Thanks for sharing this. Good job finding the problem btw! I noticed the issue when connecting a dev kit to gnd powered by the PSU. It was tripping the mains RCD. I was getting over 160Vdc from the -terminal to gnd. Same for the +terminal. The output was floating at this dangerous voltage. Anyway, I found your solution and was able to do the modification quickly. It is now safe...er. thanks again.

[Grayk]

Dear Hantek hdp135v6 users, I have some problems with this power supply. The overload protection of the 2269 chip is triggered at 77-79 watts. Even in current stabilization mode, the LEDs do not always switch from CV to CC, that is, the current stabilization mode has already turned on, but the CV LED continues to light. Also, without load, there is no 0 on the output of the operational amplifier of the current sensor. By the way, the R91 resistor was burned out, and the gasket on the output mosfet was punched, but the mosfet itself remained intact. I would appreciate it if someone could confirm that these are bugs of my instance only. And yet, I drew a diagram in the Splan7 program, I can share it if anyone is interested. True, I'm not a professional, but I think it's possible to figure it out.