# Voltage drops out on 36 v DC Power Supply

#### ZvsDC

Joined Feb 27, 2017
10
Hi everyone, I have an issue regarding a 36v 20a dc power supply. I had an issue some time ago where the trace line popped on this unit. I re soldered the trace and everything is running at 36 v when it is powered up but! when I put a load to it which has an amp rating of 8, the voltage pulses from 36v down to 2v and keeps pulsating like this. Running a dc fan is no problem or issues but anything that seems to need amps won't work right. Does anyone have some insight on why this could be happening and what I should look at here. Thanks for any help.

#### dl324

Joined Mar 30, 2015
12,871
What caused the trace to open? Is the output voltage supposed to be adjustable?

#### ZvsDC

Joined Feb 27, 2017
10
What caused the trace to open? Is the output voltage supposed to be adjustable?
Wires got crossed and the voltage has a small trim pot that will adjust voltage slightly but it is not an adjustable power supply, no. It's just that when something is hooked up that needs any kind of amperes over say 1 or 2 it pulses between 2v and 36v

#### dl324

Joined Mar 30, 2015
12,871
Does it have current limiting? Whether it does or not, something is broken.

Does it work at a lower current?

#### Papabravo

Joined Feb 24, 2006
16,083
Commercial unit or home built?

#### ZvsDC

Joined Feb 27, 2017
10
Does it have current limiting? Whether it does or not, something is broken.

Does it work at a lower current?
It is a chinese power supply so I don't think it has a limiter, but it will run say a fan that needs 1 amp will run fine

#### dl324

Joined Mar 30, 2015
12,871
It is a chinese power supply so I don't think it has a limiter, but it will run say a fan that needs 1 amp will run fine
Do you have a schematic?

#### ZvsDC

Joined Feb 27, 2017
10

#### ZvsDC

Joined Feb 27, 2017
10

#### SamR

Joined Mar 19, 2019
3,386
Sure sounds like a chinesium SMPS... They are usually considered throwaways instead of repairable. They used to repair them, but now so cheap it's usually better to buy a replacement.

#### ZvsDC

Joined Feb 27, 2017
10
Sure sounds like a chinesium SMPS... They are usually considered throwaways instead of repairable. They used to repair them, but now so cheap it's usually better to buy a replacement.
oops 16.5 amp

#### SamR

Joined Mar 19, 2019
3,386
From Fleabay. I didn't even search for the cheapest one... Good luck finding the schematic for it. All the relative info should be on the label. Not sure if you need the full 16.5A so...
Good luck trying to repair it. I'm sure there are some that are well designed and made but not sure who. MeanWell from Taiwan comes to mind but the chinese will label them anything. I even see some MeiWell...

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#### DarthVolta

Joined Jan 27, 2015
521
What does a 36VDC 20A PSU feed power to ? I guess barely I use any power, so IDK.

It must be a lot of work running the mains AC for towns, my little circuit board problems pale in comparison.

#### R!f@@

Joined Apr 2, 2009
9,747
Ur PSU is going into protection at high current even though it is lower than the rated value.
PSU is hiccuping.
If it cannot supply the rated current then there is still an issue with in the supply after wire crossing issue.
The burned track can probably lead you to a faulty component. Probably in the current sensing circuitry.

#### R!f@@

Joined Apr 2, 2009
9,747
Some pictures of the damaged track area can be of help