Chinese DIY 0-30V 0.2-3A Power Supply Troubleshooting

Thread Starter

totemos19041980

Joined Jun 26, 2020
6
Hello all,
As many of you are having problems with the same diy kit, im having the same problems.

Im using a 24v 3 Am AC as input.

From the troubleshooting thread that i read, non of the measurments are correct with my kit.

1st indication is that LED is constantly active.
With 10k pontesiometers i can change output voltage but anti clock wise is 20v and clockwise 1.1
When i try to use output to a lamp 12v nothing happens.

I have triple checked material installed and its correct. also i have even change some of the part with new one, because there was wrong.

1593505736954.png

Point A : is 33.5V instead of 32.5V
Point B: instead of -5.6v i have 326mV
Point C: is 24V Correct

Can somebody help to fix this problem.
 

ericgibbs

Joined Jan 29, 2010
10,208
hi tote,
Welcome to AAC.
Do you have a circuit diagram as part of the kit that you could post.?
I guess you have confirmed the 5V1 Zener is a zener and is the correct way around.?
E
 

Irving

Joined Jan 30, 2016
820
Point A is fine. I agree with Eric, either the zener is the wrong way round or its not a zener, is the most likely cause but there could be other issues.

Can you post a schematic or a link to it, and maybe a photo of your board alongside the example above.
 

Irving

Joined Jan 30, 2016
820
Measure volts to ground from at bottom end of R3 - 2nd resistor from left at bottom left of board. Measure volts at bottom end of D5, the diode next to it. Report back.
 

ericgibbs

Joined Jan 29, 2010
10,208
hi tote,
Downloaded your documentation, will check thru it, let you know what I find.
Did you confirm that D7 is in fact 5.1V Zener Diode.?

E
 

Irving

Joined Jan 30, 2016
820
Remeasure after resoldering, with your black lead on ground. Both voltages should be negative with respect to ground. Ground is the right hand end of the two big diode above next to the word 'LED'.
 

Irving

Joined Jan 30, 2016
820
Just run a LTSpice on that bit - those values are exactly right if the zener diode is in back to front, though I agree the pictures suggest otherwise...

Right
1593605487900.png

Wrong
1593605663297.png
 

Irving

Joined Jan 30, 2016
820
Found an image of back of board showing how everything connected

If its not the wrong way round, then it looks like that Zener is either fried or isn't a zener....

30vpsu.png
 

Thread Starter

totemos19041980

Joined Jun 26, 2020
6
one strange thing is at the positive of the capacitor down left but on the right side, im measuring 0 Volts, i have already changed the capacitor but nothing changed.
The positive side is the input of the zener 5V1
 
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