Lab power supply QW-MS3010D failing?

ScottWang

Joined Aug 23, 2012
7,397
The output set at 2Vdc with 2Vpp ripple?
Is it only at the positive side or it also at the negative side?
If you have Oscilloscope then choose a DC range which could handle over 40Vdc to measure the output of the rectifier diodes (it might be used Bridge rectifier diodes) that it from the transformer, or the input of the voltage control board, if you get the big ripple voltage then it could be the problem is at the filter capacitors.
 

Thread Starter

Erik84750

Joined Jun 15, 2017
4
Hi ScottWang, thanks for your reply! Where can I find a schematic for this supply?
My scope can handle 40Vdc, and I can see where the (rather small??) bridge rectifier sits, but I prefer to work from a schematic if possible?
Where would the voltage control part sit, which are the filter capacitors?

Thanks!

upload_2018-12-2_8-42-52.jpeg

upload_2018-12-2_8-43-10.jpeg
 

ScottWang

Joined Aug 23, 2012
7,397
The board is all in one, what I called that the voltage control part is around the two 14 Pins and 16 pins ICs.
1. Using Oscope to measure the negative power (Gnd, -V) to make sure is it ok or not?
2. What's the rated voltage and ? uf of two big capacitors?
3. Using Oscope to choose a DC range which could handle the rated voltage of two big capacitors to measure two big capacitors of the left side in the second picture.
4. What are the ic numbers of 8, 14, 16 Pins?
 

Thread Starter

Erik84750

Joined Jun 15, 2017
4
Hi dendad, indeed, that is why I need a schematic. The thread you show I had seen, thank you.
Connecting a scope to mains is the last thing I would do if ever.
So unless I find very specific information on this power supply I will not touch it any further.

The large ripple on the output worries me because of the fact that this is a switched power supply.
 

MrChips

Joined Oct 2, 2009
30,712
From what I have experienced, that power supply might be useful for powering motors, solenoids, lamps, battery chargers, and other projects where power supply noise would not matter.

It would not be recommended for applications where low noise power is essential such as logic and amplifier circuits.
 
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