ATX PSU SL-500 Short circuit can't find where? Transformer?

[smile]

Hello,

I got ATX PSU SL-500 PSU. Images Attached.
It has blown VIPER22A, that I replaced.
Connected trough light bulb the bulb glows very bright indicating a short.

I tested every component on hot side of PCB and can't find the short circuit.
However the problem goes away removing +5VSB transformer.

The winding in questions of +5VSB transormer shows 0.08Ohms, is this normal?

[Per Hansson]

Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

If you are reading 0.08Ω DC resistance on the primary winding I would say the transformer is shorted.
A normal primary side winding resistance should be around 2Ω to 5Ω
Secondary resistance would be normal at around 0.05Ω to 0.10Ω

Here two examples:
https://www.badcaps.net/forum/showpo...5&postcount=18
https://www.badcaps.net/forum/showpo...8&postcount=60

And here is a datasheet for a transformer that should have similar ratings, pinout may be wrong but you can see the DC resistance values:
https://cdn.badcaps-static.com/pdfs/...5308f3be00.pdf
From: https://www.we-online.com/catalog/en/MID-OLSTM

[stj]

Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

a ring tester or component tester that has the inductance software would be handy

[smile]

Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

Thanks for suggestions, I ordered IC BH0270A, maybe it will fix it. Also looking for replacement transformer to salvage from another PSU, but so far can't find it.

[Per Hansson]

Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

Thanks for suggestions, I ordered IC BH0270A, maybe it will fix it.

If the lamp is bright when the power supply is soft off this will not fix it.
Because the primary power supply should be off in that case, only the Viper providing 5Vsb...

But of course if the MOSFET inside the FSBH0270ANY PWM chip has failed shorted maybe that is what you where reading.
But the two transformers should be completely isolated.
And removing the 5Vsb transformer in that case would not remove the short...

Do you have a "component tester" also called "transistor tester" or a ring tester to check the transformer with?

[smile]

Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

If the lamp is bright when the power supply is soft off this will not fix it.
Because the primary power supply should be off in that case, only the Viper providing 5Vsb...

But of course if the MOSFET inside the FSBH0270ANY PWM chip has failed shorted maybe that is what you where reading.
But the two transformers should be completely isolated.
And removing the 5Vsb transformer in that case would not remove the short...

Do you have a "component tester" also called "transistor tester" or a ring tester to check the transformer with?

Well replaced the transformer for +5VSB that is for sure not 0.08ohm resistance, but the result is the same short circuit bulb shines bright. Still waiting for PWM IC.

"Do you have a "component tester" " - Have ESR meter, miliohm meter 2 wire, inductance meter, PEAK Atlas Atlas DCA Pro.

[Per Hansson]

Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

Well since you have a inductance meter why don't you use it?

[smile]

Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

Well since you have a inductance meter why don't you use it?

Maybe because I don't know what it should show as good/bad ?
The resistance is very low so what is normal values?

[Per Hansson]

Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

Here is an example from a Seasonic SS-250FS with a VEE19FRC3 5VSB Transformer:
Primary:
3.44ohm
1.85mH
444kHz
Q=9.2

Aux:
0.24ohm
0.06mH
736kHz
Q=17.8

Secondary:
0.01ohm
2.49µH
750kHz
Q=20.6

Values taken with a "component tester" so nothing fancy, but still the relative values should tell something.

[smile]

Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

Primary:
2.66ohm
1.89mH

Aux:
0.48ohm
150mH

Secondary:
0.30ohm
108µH

[sam_sam_sam]

Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

Here is an example from a Seasonic SS-250FS with a VEE19FRC3 5VSB Transformer:
Primary:
3.44ohm
1.85mH
444kHz
Q=9.2

Aux:
0.24ohm
0.06mH
736kHz
Q=17.8

Secondary:
0.01ohm
2.49µH
750kHz
Q=20.6

Values taken with a "component tester" so nothing fancy, but still the relative values should tell something.

I have a question for you that is related but with a different type of tester using a blue capacitor tester and you get a 0.00 value dose this mean that this winding might be shorted because I have used it in the past with a ring tester to find possible shorted windings with this but do not know how accurate this type of testing does because I have had a switching transformer show very low or no light on the tester which is supposedly means that the winding is shorted but the device works correctly with this transformer testing this way sometimes which I have not totally understand the results of the tester

If a component tester does a better job telling you that a switching transformer is shorted can you please send me a link to where I can buy one that does a better job doing this type of testing

Thanks

[Per Hansson]

Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

Primary:
2.66ohm
1.89mH

Aux:
0.48ohm
150mH

Secondary:
0.30ohm
108µH

Ok, in these readings you no longer are close to a dead short on the primary winding so something in your testing must have changed?
For another example here is a new transformer I bought by mistake related to this thread.


Würth Elektronik MID-OLON Offline Flyback Transformer article number: 750312279
Product page: https://www.we-online.com/catalog/en/MID-OLON#750312279
Datasheet: https://cdn.badcaps-static.com/pdfs/...dc18d6f15f.pdf

Note:
1 > 9 is Primary
3 > 8 is Aux
5 > 6 is Secondary

DC Resistance	Inductance & Q Factor				Inductance & Q Factor
UNI-T UT61E:	Agilent U1733C:					GM328R "Component Tester":
1 > 9 = 0.50Ω	730µH	100khz=Q300 10khz=Q75 1khz=Q8.0	760µH 840kHz  Q=5.0
3 > 8 = 0.08Ω	13.3µH	100khz=Q200 10khz=Q7.9 1khz=Q0.8	0.24µH 2424kHz Q=18.4
5 > 6 = 0.01Ω	2.1µH	100khz=Q100 10khz=Q2.8 1khz=Q0.3	0.22µH 2535kHz Q=5.2

I have a question for you that is related but with a different type of tester using a blue capacitor tester and you get a 0.00 value dose this mean that this winding might be shorted because I have used it in the past with a ring tester to find possible shorted windings with this but do not know how accurate this type of testing does because I have had a switching transformer show very low or no light on the tester which is supposedly means that the winding is shorted but the device works correctly with this transformer testing this way sometimes which I have not totally understand the results of the tester

If a component tester does a better job telling you that a switching transformer is shorted can you please send me a link to where I can buy one that does a better job doing this type of testing

Thanks

To better understand your ring tester please watch this Youtube video linked below.
As you can see even one shorted ring causes a very big drop in ring oscillations, of course such a transformer still works, only a bit worse compared to when it was new.
It is a good way to test transformers when you don't have access to a datasheet that actually tells you what the values should be, that is its main advantage...
If you look at my values in the code box above here you can also see how much it differs from meter to meter: much better to have a meter that gives a more definitive result...
P.S: The ring tester is also available as an addon for the component tester if you use the M-firmware from madires that you can build yourself:
https://www.youtube.com/watch?v=QBbEYYWiBI8

[smile]

Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

Well I found similar transformer in another PSU, and repalced it.
My meter measures only uH,mH value, and resistance.

The readings are in post above.

The PSU did not start, in fact the short circuit was still there.
I could not find. The VIPER22A was overheating 100deg C.

[smile]

Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

Afterwards I decided to see what would blow if I connected direct to mains.
This is what blew, magic smoke came from Viper22A, diode next to it.

[smile]

Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

I changed the Viper22A and diode from another PSU. The Transformer was also changed (to blue colored one the resistances are not as close to the posted above) as the first one had 1ohm on primary after magic smoke came out from other parts.

But after connecting trough the light bulb the thermal camera shows overheating capacitor. Connecting to mains direct makes the cap explode with loud bang

[smile]

Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

The transistors on primary side heatsink were desoldered and tested OK.
The Viper22A is unknown condition.
Diode near viper is OK.
All other coponents on primary side are OK with testing using multimeter without desoldering. Any ideas?

[petehall347]

Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

throw the safety light bulb away and keep blowing everything up first try .

[smile]

Re: ATX PSU SL-500 Short circuit can't find where? Transformer?

throw the safety light bulb away and keep blowing everything up first try .

I think you did not read whole thread, all components tested OK that is why I removed the bulb. If I had a variac I would use lower AC voltage to see what heats up. But sometimes it is more easy to let parts explode then to find the problem.