Start up not reliable.

  williamj 09:38 08 Jan 2011
Locked

When I press start the power and hard drive neons show and the fan starts, but then stops.
After 3 - 4 starts the start holds and no further problems.
I have checked the motherboard power connector and it is making a good connection.
Clock is keeping good time so I assume the motherboard battery is still good.
Any thoughts on checks to make please?

  rawprawn 10:04 08 Jan 2011

Start switch?

  Terry Brown 10:36 08 Jan 2011

Do you mean the fan on the Power Supply Unit (PSU) or the fan on the Processor (CPU).

If on the PSU, I'm guessing the unit is on the way out, and needs replacing.

If on the CPU, check the cables from the fan to the motherboard, as they may be frayed or loose.

Terry

  williamj 10:40 08 Jan 2011

Thanks rawprawn. I have checked the plug to the System Panel which is activated by the start switch and the start button makes and breaks positively to that connection (PWRSW)

  chub_tor 10:41 08 Jan 2011

rawprawn is correct as a sticking power on switch will give exactly that effect, failing that it is the power supply. But my money is with rawprawn.

  williamj 10:52 08 Jan 2011

Terry,
On pressing START both Power supply fan and processor fan start, and then stop.
I am thinking power supply too, but don't know what terminals on the motherboard connector activate the power supply, and don't know the circuit to the power supply.
Is there any way to check the power supply independently?

  williamj 11:23 08 Jan 2011

As the problem is getting a first time start I agree that the start button is suspect, but I have checked it makes positive contact, and breaks positivly on release, so I think I have eliminated the start button.
Then on getting a good start the power supply continues with no problems.
The fault I want to identify is why will the power supply not start on the first press of the START button.

  Fruit Bat /\0/\ 13:42 08 Jan 2011

struggling to start from cold

Classic sign of a failing PSU

Explanations can get complicated but power capacitors are one of the first things to fail.

  williamj 15:25 08 Jan 2011

Thanks everybody,
I have ordered a new power supply, and will confirm if the new power supply solves the problem.

  williamj 20:59 11 Jan 2011

New power supply fitted and problem solved.
A point about connections from a power supply.
The old supply had all WHITE connectors for C/D's, Floppy and Hard Drive, but the Hard Drive needed a BLACK SATA connection, and an adapter cable was needed to give the SATA connection.
The new drive had only 2 WHITE connectors and 2 BLACK SATA connectors, so I was O.K.
The connectors for processor Fan and Floppy were as normal.
So if purchasing a Power Supply make sure the connectors on the Power Supply suit your Hard Drive.
I will mark resolved soon in case there are some more comments.

  woodchip 21:01 11 Jan 2011

As above the PSU is on its way out, its taking time to warm up before it will keep running

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