[weeGeordie]

I'm not sure if the power supply is bad or the on/off switch is broken. Can I test the switch by putting a screwdriver blade across a couple of the wires? If so, which colour wires?

[norton850]

Yes you can put a small screwdriver across the pins on the motherboard. Just trace the wire from the front power switch for the correct pins. It's usually labeled also but can be hard to see.

[I Fix 4 U]

Isn't this dangerous to yourself and the computer?

[weeGeordie]

Don't I have to bypass the switch, (ie: take power from the wires coming from the power supply)?

[gotrootdude]

take the wire from the power on switch off the motherboard and replace it with the reset switch wire. Then use the reset switch to power on and off.

[CarlssonMB]

If you are testing if the power supply is bad, put the switch in the on position and take and take a volt meter and put the red end in the red wire of the 20 pin psu > motherboard connector and the black end in the black wire of the psu > motherboard 20 pin connector.

If the PSU is dead, nothing will happen. If it is not pressing the red wire and black (ground) will kick the psu fan on.

And as always while working with electrical, be careful not to electrocute!

[CarlssonMB]

also look at this:

http://www.extremeoverclocking.com/a...y_Guide_1.html

[norton850]

If you are just testing the switch on the front of the case either the screwdriver method (yes it is safe just use reasonable caution) or switching the wire with the reset one will eliminate the front panel switch as the case of the problem.

[weeGeordie]

I was gonna try to test the PSU until I discovered there are 7 black wires and 3 red wires on the connecor to the motherboard.

[weeGeordie]

I tried a jumper between the green wire and the adjacent black wire on the mobo connector and the fan started up. Does that mean the P/S is OK?

[norton850]

You really never said what you problem was, but I would guess nothing was happening when you flipped the power switch. You've determined that the PS isn't dead, but we don't know that it's OK. You still need to test the case switch.

[weeGeordie]

I found a post that talked about a jumper between the green and adjacent black wires on the motherboard plug. I tried that and the fan on the p/s started. I plugged it into the motherboard and jumpered the green/black again and both the fan on the p/s and the fan on the cpu started.

There are 2 sets of yellow/black wires going from the front panel power on/off switch to the motherboard. I removed the plug on the motherboard and used a screwdriver to connect the pins on the motherboard that those wires go to, (both sets). No response.

[norton850]

I sure could be wrong but I don't think there's any standardized color coding for case wires. Someone else will need to comment about two sets of wires from the case switch, usually there's just one set. The clip at the end of the power switch wire (where it attaches to the MB) ususally says "power sw" or some abbreviation of that.

[weeGeordie]

Sometimes I think if it wasn't for bad luck I wouldn't have any luck at all. I've given up on trying to figure out if it's the power supply that is shot and decided to buy a replacement and hope for the best.

Taking a closer look at the unit it appears to be an odd size. It's an ASTEC model AA21480 from an IBM NetVIsta system and it's smaller than the power supplies I'm used to seeing. It also vents inside the system case rather than outside. It mounts on a special rail which then attaches to the back and the inside of the case.

[weeGeordie]

I think your right norton850. I've looked inside the case of another system and the colours are different.

I checked a motherboard manual at the IBM web site and it said the connector from the case switch should be in a different place than where my wires go to. When I look closer there is indeed a set of connectors with labels indicating power, speakers, etc right where the manual says it is.

Why the wires on my system go to a different connection on the motherboard is beyond me.