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#21 | |
Badcaps Veteran
Join Date: Oct 2015
City & State: Cambridgeshire
My Country: U.K.
Line Voltage: 240VAC
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#22 | |
Badcaps Veteran
Join Date: Oct 2015
City & State: Cambridgeshire
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#23 |
Great Sage 齊天大聖
Join Date: Dec 2009
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![]() 8pin chip
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#24 | |
Badcaps Veteran
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VISHAY-EPCOS-METAL-OXIDE-VARISTOR-150v-QTY-5/123787501997 3-Metal-Oxide-Varistor-MOV-20D431K-275VAC-120/121769194537 Varistor-76-0J-300V-ac/391288103662? Varistor-38-0J-250V-ac/391741394396? |
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#25 |
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Join Date: Oct 2015
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![]() There two 8 pin chips in this thing but only one with 384 in its number. The one in this photo I hope.
I was unsure where to put the negative probe so put it on the "-" of the rectifier. Doing this I didnt get any voltage reading. |
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#26 |
Great Sage 齊天大聖
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![]() 250v is my choice, pay attention to the diameter.
bigger is better - if you have room for it! |
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#27 | |
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One pin of the transformer primary will be connected to the main cap +. The other pin of the primary connects to the mosfet Drain, and there should be a low ohm resistor from the fets source pin to hot ground (main cap -) Last edited by R_J; 11-18-2020 at 05:54 PM.. |
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#28 | |
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I did try to see if I could get a connection between the Mosfet (drain and one of the connections on that small transformer but couldn't get anything. Anyway I removed the Mosfet (WN9K90Z) for testing and testing it with a multi-meter in diode mode, I got a open circuit between source and drain but if I touched the positive lead to gate to charge it the source and gate still remained open circuit which is not right. So I put my component tester on it and it correctly identified it as a Mosfet (see photo) so that must mean its OK I think. Did anyone find a schematic for this PSU, I couldnt? |
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#29 | ||
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Join Date: Aug 2005
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Returning to my comments above, once you figure out the problem with the 5VSB circuit, if you have a 3.3V wire in the -5V location, the power supply is not compatible with your ATX PSU tester. I'm pretty sure Delta used the Power Integrations regulators for their 5VSB circuit, possibly from this series, https://www.power.com/sites/default/...tny274-280.pdf or this series, https://ac-dc.power.com/sites/defaul..._datasheet.pdf . If you look at the sample circuit on page 8 of the first data sheet, look for components equivalent to R5, R3 & R8, C6, and VR2 and check them out. Those have to do with the the start-up and operation of the IC.
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PeteS in CA Power Supplies should be boring: No loud noises, no bright flashes, and no bad smells. Where might is right There is no right. - Sophocles in "Antigone" **************************** All that is gold does not glitter, Not all those who wander are lost; - J.R.R. Tolkien, The Fellowship of the Ring **************************** To kill personal responsibility, initiative or success, punish it by taxing it. To encourage irresponsibility, improvidence, dependence and failure, reward it by subsidizing it. |
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#30 |
Badcaps Veteran
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![]() Thanks for that Pete, I think this is standard atx as I just compared its atx connector pinouts with a picture online and it shows one position empty which is the -5v line.
Here is a photo of thhe 20 pin connector. I have 6 of these desktops to fix the domed caps and ive done 4 of them and they are all working. This is one of the remaining 2 psu's' to fix. |
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#31 |
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![]() This redistor doesn't make sense.
Its colours are: Brown Green Silver Gold White I measure it at 0.76 ohms But this combination of colours doesnt make sense on any 5 band calculator. |
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#32 |
Great Sage 齊天大聖
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![]() it's wirewound - the fact that it meters low ohms means it's o.k.
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#33 |
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#34 |
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![]() Brown
Green Silver Gold 0.15 ohms |
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#35 | |
Badcaps Veteran
Join Date: Aug 2005
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#36 |
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![]() I believe the mosfet you removed is for the main supply not the standby, the transistor for the standby circuit is near R905
Last edited by R_J; 11-20-2020 at 08:48 PM.. |
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#37 | |
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#38 |
Badcaps Veteran
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![]() The incandescent lamp in series would have saved one of the psus from blowing. You can google it and always connect it in series with the psu when you test psu like this in the future.
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#39 | |
Badcaps Veteran
Join Date: Oct 2015
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Can i test it in place before changing it? |
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#40 |
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![]() The small smd transistor drives a larger mosfet that has it's Drain pin connected to the small standby transformer, I made a Red square around the standby mosfet and a yellow one around the drive transistor.
On the small standby transformer, pin 1 should have 160vdc, and so should pin3 which is connected to the mosfet drain., this is the primary. There is likely a low ohm resistor connected to THIS mosfet's source pin to hot ground. Last edited by R_J; 11-22-2020 at 04:24 PM.. |
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