Computer Power Supply Repairing

[Suraj143]

Hi all I’m having a trouble with my computer power supply (250W).Every time I switch the PSU the main trip is going.when I was checking inside the PSU the bridge rectifiers (four diodes) has a big short.

1) I want to know that can I replace the diodes with 3A diodes. Because it’s hard to find the same number in my area.

2) And if somebody has some links in computer power supply diagrams, troubleshooting can you please provide.

Thanks a lot

 

[Sceadwian]

What is the AC input voltage? 120 or 208/240?

 

[Suraj143]

Its 230V AC input

 

[mneary]

The bridge diodes usually aren't the first components to fail. Check the input filter caps and power transistors before replacing the diodes.

 

[Suraj143]

Hi mneary I checked that Caps & Power transistors they were ok. There was a big leak in the four diodes.
Can I replace the diodes with 3A diodes?

 

[Nigel Goodwin]

Hi mneary I checked that Caps & Power transistors they were ok. There was a big leak in the four diodes.
Can I replace the diodes with 3A diodes?

Should be fine, as long as they are high enough voltage?.

 

[RODALCO]

Get the 1000 V ones.

1N5408 are rated for 3 Amps at 1 kV, They cost about 30 cents each.
Available from most electronic shops.

 

[Hero999]

The higher the voltage rating the better, 400V minimum, 1kV is good, 2kV is excellant as the mains can have up to 2kV spikes on it.

 

[kruno]

Hi Suraj143.It is not necessary to take hi voltage diodes.200V 3A will be O.K.
Of corse,new power supply is not too expensive .
Kruno

 

[Nigel Goodwin]

Hi Suraj143.It is not necessary to take hi voltage diodes.200V 3A will be O.K.

Not by a LONG way - with 230V mains you're looking about 340V DC output, I would seriously suggest 1KV 1N5408 rectifiers - in fact I only stock the 1N5408. 200V rectifiers would blow instantly at switch-on.

 

[kruno]

Not by a LONG way - with 230V mains you're looking about 340V DC output, I would seriously suggest 1KV 1N5408 rectifiers - in fact I only stock the 1N5408. 200V rectifiers would blow instantly at switch-on.

Hi Nigel Goodwin.The bridge, as you know, it has 4 diodes.2 diodes are in series and other 2 diodes are in series too.If you use 2 diodes 200V,because they are in series they can work in range of 400Volts.The other 2 diodes too I think. Sorry for my English.
Best regards, Kruno.

 

[Nigel Goodwin]

It's a nice theory - but the diodes go BANG if you try and do that. While it looks like the diodes are to some extent in series, they aren't really - and if they were, you would need voltage balancing reistors across them.

 

[kruno]

It's a nice theory - but the diodes go BANG if you try and do that. While it looks like the diodes are to some extent in series, they aren't really - and if they were, you would need voltage balancing reistors across them.

If you say so probably it is..