Mother board problem

[boofhead]

I put a new MB (PC CHIPS) with P4 etc and a 400W power supply in and I get nothing when I try to turn it on, the power supply fan does not run, no lights, no sounds, nada.
I am assuming a MB fault and intend to send it back, but before I do, has anyone any ideas as to other reasons for this to happen? I tried putting the case switches onto different points on the connectors, thinking they might have been mislabelled, but did not help. Although there are only two pins for the Power LED and the plug from the case is a three pin one (using the two outside pins, of course) so I have left it off, would that affect power up? It is a mini ATX board and the only power is the main one, the aux plug is not used. frustration!

[spannersatcx]

Check the fuses,
Is the switch by the power supply on,
Is the on/off switch connected to the MOB correctly
Is the power supply for a P4 MOB,
Check and recheck all connections,
Try another power supply,
:)

[Squiddley]

The PWR connector is a prime suspect. Have you got it on the correct pins (and orientation?)

Also, is the motherboard seated and screwed on properly, using the "right" screws/plugs? (Applies to everything else too) A short could be the cause, as most MBs have protection against such a situation. I'm always left with spare screws after an assembly :confused:

[MasterGreen]

Before you take the MB out and all that. The fact that the Power Supply fan is not running is a critical point.

Modern Power Supplies are started through a contact trigger and this is probably where the problem lies.

The ON/OFF switch is really just a trip switch to send a signal to the PS to go active. Providing there is power at the back and the little switchat the back is on (excuse me being pedandic - but I have lost precious hair over this myself). Check the connection to the bottom of the motherboard to your Power Switch - and the main power connections to the board. Remember that P4 boards now use the long block connector (pretty hard to get wrong) and a small +5v/-5v 0v square connector. The power ON/OFF connector one is not polarity sensitive, but those little pins can be sods to identify.

If you are convinced that all the above is OK - then the next obvious suspect is the Power Supply itself. Borrow, beg, rob another one and try that.

Then bin the MB....

[RomeoTangoFoxtrotMike]

Computer power supplys are of the "switched-mode" design (this makes them smaller and more efficient than traditional supplys.) However, earlier models didn't like being operated without having a load connected (it's a bit like it being very easy to over rev. a car engine when it's in neutral) Modern supplys should be fully protected against that, but unless you've got a technical spec which confirms this, I would err on the side of caution.

Why do I mention this ? well, if you've got a dodgy connector, and you haven't actually managed to connected the PSU up to the motherboard, you might have managed to fire it up unloaded, possibly damaging it :rolleyes: (I have dead disk - well, the motor's OK - which I plug in to new PSUs so that there is always something there to load it...)

HTH,

[ There was one model of PSU that I came across that had output protection in the form os a fuse inside the PSU case, so if it blew, you couldn't replace it without opening the case and invlidating the warranty... :( of course, once it was out of warranty :) ]

[Lost_luggage34]

Also worth ensuring that the PSU is up to the job - at 400W it should be unless you have a full load of power hungry cards & external devices.

Had an identical problem when I replaced my motherboard. Fitted a more powerful PSU and problem solved.

[boofhead]

Thanks for all the help, it is amazing.
I tried the MB in a different computer case with its own power supply with the same result. I tested the power supply output and it is giving 4.8 volts on some of the outputs so it is working OK (I am pretty sure). I tried the power connector both ways and also varied the position on the board, also tried the reset switch in case they had the diagram wrong. This board is an ATX but it only uses one power connector from the PSU. I rang the tech support and they confirmed there was only one connection. They suggested I reflash the bios whicb I did, but I cannot see how the bios would give this problem. Would bad memory cause the board to fail to light up?
I suppose I must have fried it with static electricity or something, although I tried hard not to. I only use four metal screws to hold a board, and use plastic otherwise. I was advised that the metal connectors do not need to be insualted from the board, since the connector points are electrically isolated. Learning all the time.
But hey, thanks a lot.

[ORAC]

If it's not a silly question:

1. How did you many to reflash the BIOS if the machine won't boot? (unless you're lucky enough to have an EPROM burner!)

2. How did you manage to "vary" the position of the power connector on the motherboard? It's designed as to only be able to be fitted in the correct socket.

3. If it's a new P4 motherboard, I'm surprised it has it only got the old single power connector. Does it have the two newer power connectors as well - and what does the power supply have?

4. What, exactly, is the motherboard model?

The voltage means nothing on it's own. You need the full figures. See here (http://www.pcguide.com/ref/power/sup/output.htm)

p.s. If you've been sticking a live power lead, at random, over pins connectors I would consider it as almost absolutely certain you've blown it - and it's got nothing to do with static electricity!!

Try taking both the board and power supply out of the case, connecting them, and then short across the power on pins with a screwdriver. If the power supply starts it's probably a wiring/earth fault. If not, you've probably fried it. Hopefully the CPU and memory will be OK, but you might have fried them as well. Keep your fingers crossed!!

[boofhead]

The MB is a PC Chips M925 and is a micro ATX. It is smaller than most boards and has only one 20 pin power socket. It has no provision for the secondary cable to be attached.
The switch and LED connectors for attaching the cables from the case show the correct position of each, but I tried reversing the plugs and putting the power cable (the one from the case switches, not from the PSU) on the reset pins, even though they are not polarity sensitive, but it had no effect.
I asked the tech support and they suggested that I try to clear (sorry, not flash) the bios by setting the jumper, applying power for a few seconds, then shutting down and putting the jumper into the normal position. Again, it had no effect.
I will try the suggestion of removing the PSU and board and attempting to get some response from the PSU, as you point out, it is a mighty complicated beast. No fuses that I could see, and the board did not work in another case either so I suspect it is the board, not the power.
Anyway, I appreciate the replies.

[Lost_luggage34]

I really think that your problem is PSU related.

All very well having the 4.8V but have u got all the correct voltages with reference to ground 0V ?

I forget the exact details but the motherboard has to have +12V, -12V, +5V , and -5V with reference to a good ground 0V

Hope that helps a little and that you haven't fried it - fairly unlikely and also pretty unlikely that you fried it with static during the install unless you were running around on a nylon carpet with trainers on at the time !!

Good luck

[tony draper]

Most modern MB and PSU'S need to see a short across two of the pins, unless they get a momentary short the power supply will just sit there doing nothing.
Make sure all the cable from the case IE power on , reset, ect are connected to the correct pins on the MB.