PSU M/B question

  Catastrophe 09:07 09 Sep 2010
Locked

If you have a working PSU and a (presumed) faulty M/B would you not expect a fan connected directly to the PSU (not via M/B) to work.

Is there anything which could stop the M/B showing signs of life? (e.g., light on board, CPU fan working?

Thanks for any answers.

:)

  Graphicool1 09:34 09 Sep 2010

"would you not expect a fan connected directly to the PSU (not via M/B) to work"

How do you know that there nothing wrong with the fan?

What prompted your question?

  woodchip 10:54 09 Sep 2010

A Fan is only part of the equation, and does not need much power to run. Also there are different volt lines that come out of a PSU only way to test properly is while connected. If you have a volt Meter you can Back Probe the main Motherboard Plug for Volts when Switched on, click here you cannot get a shock as volts are only low you can check volts along with what it says on the PSU on Tolerance Values + or -

Testing a PSU without being connected i.e a Load on it can blow a good PSU as they are Switching PSUs and are only made to work with a Load. Having lights on front of case working or on Motherboard and fans working is no indication that the PSU is any good. as these only need small currant

  Catastrophe 10:57 09 Sep 2010

"would you not expect a fan connected directly to the PSU (not via M/B) to work"

Q) How do you know that there nothing wrong with the fan?
A) I have tried another fan with same result. Both were workinat fan directly connected to recently. I will, however, test in another PC to check.

Q) What prompted your question?
A) I bought a M/B with CPU and RAM and initially it powered up. Then blank. Checked PSU - OK. I noticed the fan connected to PSU was not working so I am wondering whether the M/B might be OK and something else is wrong.

:)

  Catastrophe 11:39 09 Sep 2010

Graphicool1

I have tested second fan and it works fine on another PC. Did not test first and fixed in PC and second did work.

:)

  Catastrophe 11:43 09 Sep 2010

woodchip

The PSU was not switched on unloaded. Result same with another PSU. Subject PSU lit up another M/B and powered fans. I do not have a voltmeter.

If I understand that is not enough so will try PSU in another context.

:)

  Catastrophe 07:11 15 Sep 2010

woodchip

"Testing a PSU without being connected i.e a Load on it can blow a good PSU as they are Switching PSUs and are only made to work with a Load. Having lights on front of case working or on Motherboard and fans working is no indication that the PSU is any good. as these only need small currant"

OK I bought a rolson YX-1000A. Probably should have bought a digital but this will do to learn. I understand how to put probes in molex or main 12 pin and will try this later. Is it sufficient to connect a HDD to put load on the system.

I understand this will check PSU. Can anything similar be done to check M/B or if PSU is OK is M/B then faulty?

Many thanks for your reply.

:)

  Catastrophe 11:35 15 Sep 2010

^
Any comments olease?

  woodchip 12:02 15 Sep 2010

You have several different volt rail's in the PSU all should be loaded for safety of the PSU when testing one. you can buy a psu tester from Maplins, but it still not like trying one in working conditions

  Catastrophe 14:35 15 Sep 2010

woodchip

Thank you for that. It seems I am looking in the wrong area since I am trying to test a (broken?)M/B. If I start with a new PSU and the M/B is dead could I then kill the PSU if there is no load? How else to test a potentially dead M/B?

I was (wrongly) assuming that if it lit up and the fans worked it was not dead. Where from here?

:)

  woodchip 16:06 15 Sep 2010

Don't think it will kill the PSU, other way round happens most. When Power supply goes it can take out Motherboard and or CPU and drives etc. But some PSU's are better than others at protecting other hardware in case it fails. But if you have a dead system as you Have, first thing to try is a Working PSU

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