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problem with DC Power supply

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Hi all of them
i am facing a problem now a days
problem is that i had bought a power supply from market, and it makes PROBLEM from the FIRST day i had bought this
well PROBLEM is that, when i Swith ON the supply, display(DIGITAL VOLTMETER) works, but showing 0000 VALUES
when i vary from KNOBS, then nothing is going to happen
i open the POWER SUPPLY, and check fro the whole circuit that might be, if any thing burnt in it, then i must reploace, but every thing is OK from INSIDE
i study this supply since last week but uinable to LOCATE the EXAXT FAULT
if any one of you have any IDEA about this FAULT then must told me
i also mention that, i CHECK VOLTAGE from DIGITAL MULTIMETER at different part of power supply, it SHOWS (20V DC) which mean that transformer is OK....
so plz help me about this issue
waiting

TAYYAB
ELECTRICAL ENGINEERING STUDENT
 

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Chippie

Member
Any idea about what?

A dc power supply is just that...

There is a transformer, check the ac volts on the secondary...

There is a bridge, either a full bridge of four diodes or 2 diodes if the transformer has two secondary windings..Then there is a reservoir capacitor on the output of the rectifier assembly...Measure the dc voltage across it...

Lets us know what you find when you do these measurements...
 

audioguru

Well-Known Member
Most Helpful Member
The photo shows the problem, "Made In China".
Don't buy no-name-brand cheap junk.
 

Chippie

Member
The photo shows the problem, "Made In China".
Don't buy no-name-brand cheap junk.

Ooooohhh so harsh AG :D

Having looked at the first picture, if there's no output from the power supply,I'd put money on the series element being o/c...or something there abouts..
 

audioguru

Well-Known Member
Most Helpful Member
My son bought cheap Chinese junk on E-Bay.
Of course they don't work. Some items obviously were not even tested by the factory because they were missing important parts.
 

Chippie

Member
So much for quality control then eh?

The op doesnt seem to be in a hurry to get his fixed.. :)
 
Last edited:

mneary

New Member
Look carefully a the black wires that go from the transformer to the green board. One of them doesn't look properly soldered.
 
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