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smps working

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koolguy

Active Member
Hello,

How to troubleshoot not working smps.
Power rating:
+5V 40A -5V 0.5A
+12V 20A -12V 0.5A
+3.3V 28A +5VSB 2A
 
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I have never repaired smps that why i was asking?
What more details needed?
it has HS8108 is a power supply switching mode controller IC for desktop PC
 
SMPS is a fine art.... Very difficult to repair if you haven't done it before!!

Look here!! https://www.powersupplyrepairguide.com/

If you google "switch mode power supply repair " there are many hits..
 
Unless its a special app better bin it and fit new, a newun costs less than a set of switching trannys.

My usual is to check the i/p rectifier, and the dc bus, then verify there is a waveform on the o/p fet or trannys, if not see if theres control volts to the smps chip, if there is then see if the osc is running, then onto the feedback network.

Honestly though if you have never messed with an off line smps then dont, they are very dangerous and you could easily end up toasted.
 
If its a TL494 or equivalent like a KA7500 or AZ494 they're fairly easy to trace and 'hijack' for different voltages and current limits. But the HV side is risky to play with.
 
has the input fuse gone?
Has the mov become a short circuit.
Has the diode bridge gone.
Has the ntc gone open?

Thats where i woudl start.
 
has the input fuse gone?
Has the mov become a short circuit.
Has the diode bridge gone.
Has the ntc gone open?

Thats where i woudl start.
Fuse it not open, no idea of other.
 
RK!!! Your first search is for electrolytic caps gone south..

images


Caps bulge when they are damaged.... SMPS common fault....
 
yes, this is why smps with electrolytics in them cannot be potted, because it stops pressure release from overheating electrolytics.
 
A general reminder is that most SMPS's require a minimum load, sometimes on just the highest power output. Also remember that PC supplies have a signal that has to be set to turn it on. There could also be supplies within the PC SMPS that's on all the time.
 
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