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| Thread ID: 29082 | 2003-01-09 08:24:00 | Power Supply Experts - Help please | Curly (487) | Press F1 |
| Post ID | Timestamp | Content | User | ||
| 112420 | 2003-01-09 08:24:00 | I need to confirm, (or otherwise), if an ATX power supply is actually working. If I take the power supply totally out of the computer, apply mains voltage to it and with the aid of a multimeter test the HDD connectors, or the floppy drive connector, should I get a reading ? I understand that if I get the multimeter probes round the wrong way and the power supply is working, then the meter needle will deflect backwards. But even that will indicate that it is working. Once I confirm that it is working, I can then proceed to check that the voltage outputs are correct. I would have the mulitmeter range set to 50volts DC to start off with. I have not done the above as yet, but thought I would ask you Guys and Girls, first. Second question.... The computer power switch is connected to the motherboard, how does this signal the power supply to switch on? As always, any help, advice or suggestions appreciated. |
Curly (487) | ||
| 112421 | 2003-01-09 08:31:00 | The power supply will need a load before it will power up. If you search PF1 there has been a lot of discussion on this very matter about a month ago. The switch pulses the unit into life when a minimum load is present on both the 5v and 12 v rails usually |
godfather (25) | ||
| 112422 | 2003-01-09 08:41:00 | You can turn the PSU on without the motherboard by shorting the PS-ON wire (green) to one of the black wires on the ATX connecter. I've never tried checking one with a multimeter, I just connect a fan or CD-ROM to it. |
bmason (508) | ||
| 112423 | 2003-01-09 09:07:00 | For simplicity you should be able to check it without removing it from the case. If everything is plugged in there should be enough load from fans etc to start it up and you can check for the 5v & 12 volt rails on spare connectors, or if there are none, pull the floppy drive power connector off and measure there. Outside the case, the power good signal is unecessary because it is meant to talk to the motherboard, not the PSU. A single 12 volt car tail-light bulb is my 12 volt load of choice because it draws a reasonable current and gives a visual indication that the PSU is working. Usually I find that the cooling fan won't run until the load is connected and that is another good indication if you don't use a bulb as a load. Cheers Billy 8-{) |
Billy T (70) | ||
| 112424 | 2003-01-10 09:38:00 | Thanks for the replies and advise. Meantime..... I purchased another power supply, put the old computer back together and wouldn't you know it - both power supplies work fine. Damn, more money down the drain!! However.... My new secondhand m/board and CPU still don't go, but thats another question. Gota try and sort it out myself first - begging for help comes later. :-) |
Curly (487) | ||
| 112425 | 2003-01-10 10:11:00 | Remember Curly, if your motherboard expects a Power_Good signal from the PSU, it will not allow the CPU to boot until it sees it. | godfather (25) | ||
| 112426 | 2003-01-10 19:10:00 | Thanks Godfather. As I am using a known/ proved good power supply, does it follow that the 'power good' signal will automatically be generated? I presume that one of the power supply's wires is involved as the transmission vehicle. As it stands at the moment, on switch on nothng at all happens - no lights, no noise - just nothing! Wonder if you have a reference to this 'power good' signal that I could read up on to further my knowledge :-) You and your fellow 'helpers' are a real asset to this forum. |
Curly (487) | ||
| 112427 | 2003-01-10 23:04:00 | Just go to Goolge and search for power_good psu There is heaps of info. The motherboard should recognise it, provided the PSU does generate one. Sometimes a reset on the system will induce a start if the power_good is missing |
godfather (25) | ||
| 112428 | 2003-01-11 01:59:00 | One of my books suggests that this Reset trick "works" because of cheap and nasty PSUs which give PowerOK too soon. The power isn't OK. :-( But by the time you have sworn at it, and done the reset, the power is up. | Graham L (2) | ||
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