power source connections

[FlashDude]

So you replace the PSU and you tested the power switch on the case or jumped the motherboard pins for the power switch and there still is no power then the mother board is toast. There's only one test left that's unhook everthing from the motherboard. IDE cables, FDD cables, power cords from all devices, remove any add on cards (video/sound/modem/etc) and remove all the ram if the power supply doesn't start then the boards bad. I have read threw and am a little confused about your jumpstarting of the PSU. Did you take a small piece of wire or a paperclip and jump the light green wire with any black wire? If you did that and the PSU fan didn't start that PSU is bad.

 

[walkinman86]

Ok, I have acquired a new DMM and have backprobed the 20 pin connector with the PSU plugged in but the computer NOT turned on. On the #9 pin I get a reading of 4.9 VDC. which from what I understand from others that is what I should read under those conditions. Unless I am mistaken, that exhonerates the PSU as the source of the problem. I understand that a faulty Motherboard or Ram stick might also be the cause of the problem. Short of buying new Ram, is there any way to trouble shoot it? How about the Motherboard; how can I trouble shoot that?
My next step, unless there is some shortcut, will be to disconnect everything as FlashDude suggests and try starting the computer.
When I said I tried to jumpstart the computer, what I did was to disconnect the on/off switch from pins # 6 and 8 on the "Front Panel Connector", and jump across them using the using the probe end of a disconnected test probe. It did not start the computer. fans, or anything else.

 

[FlashDude]

To further test the PSU and is really the only good way to test it. Unplug the power connector from the motherboard. Connect the green and black wires on the power connector with a paper clip or a piece of wire. If the power supply fan kicks in, the power supply is probably good and your problem is likely the motherboard. If the fan on the power supply remains still, you may just have a dead power supply.
To test a ram stick Just remove it. If the PC starts the ram is bad, and this goes for all other parts as well. It is not very complicated and really should take 5 minutes to figure out what is wrong.

 

[walkinman86]

Ok, I believe I have elliminated the PSU as the problem. I have a new unit in there and it seems to check out. I have disconnected all drives and peripherals, and tried to power up.... no soap. I guess it's beginning to look like either the motherboard or CPU. Any insight? Any way to isolate one or the other? By the way, could a dead cmos battery keep the machine from powering up? I mean, if the Bios settings were lost due to a dead cmos, might that cause the problem I'm having?

 

[walkinman86]

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Ok. I have replaced the PSU with a brand new working unit. Accordingly, I believe I can eliminate that as the problem. The "Front Panel Connector" block is connected as follows: the connector labeled "HDD Led" is connected to pins #1 and 3; the connector labeled "PWR Led" is connected to Pins #2 and 4; The connector labeled "PWR Sw" is connected to pins #6 and 8. I have stripped the board of all drives and peripherals and tried to power up. No good. I have pulled the CMOS battery and checked the voltage with the DMM; it reads 3.04 VDC.
How about Jumper Settings on the Motherboard? the Board is an Intel D-845GVSR, could incorrect jumper settings keep the machine from powering up? If the problem is in either the CPU or the Motherboard, is there any way to determine which ,(if either), of those 2 components might be at fault?

 

[walkinman86]

I disconnected the main power molex and jumped across the green lead and a ground; the PSU fan began to run. I reconnected the main power molex, (the 20 pin connector), and back probed the #9 pin; I got 5VDC. I removed the "PWR SW" leads from the front panel connector, and jumped across the #6 and 8 Pins; the computer still did not start. I replaced the RAM with a known good stick; no good. I disconnected all drives and periferals and tried to power up; no good. Lastly, I have physically removed the motherboard, (leaving all connections intact),placed it on a cardboard box, and tried to power up----- again, no soap. At this point, I think either the motherboard or the CPU is toast. Perhaps a shotgun is now in order. I want to thank you FlashDude, You have been both patient and helpful, with me, and I do appreciate it.

 

[FlashDude]

No problem! As long as you have the correct two pins for the Power switch the board is toast. How ever be very wary of the PSU that was originally in that box because it is what more then likely killed your board. In other words take the shotgun to both the board and PSU.

 

[walkinman86]

Re: mebbe no shotgun yet.......

I LOVE this stuff. It's almost like a "virtual Rollercoaster". This morning, I took the MB to a local Computer repair shop, and asked him what he thought. After listening to what I had already done to diagnose the problem, he said " Man, you're pretty good. You've already done most of what you should do", ( KUDOS to YOU, because I am only the Helen Keller of computer Diagnostics.
Any way, he pointed out that most newer CPUs have a fail safe built into them in that if the heat sink fan doesnt start, neither will the CPU, and the system wont power up.
Accordingly, I brought the motherboard and CPU home, removed the Heatsink fan, and connected it dirrrectly to a 9 volt battery. The fan turns.
The way I figure it, this means that either the CPU or the mother board is toast, (kinda where I was last night).
In order to remove the CPU from the motherboard, (and maybe later reinstall it), (this would be the LAST test to determine which has "Gone South" on me, IE: motherboard or CPU), I will need some Thermal Dispersant Compound.
I've searched the internet and can find no vendors for Nanotherm Silver XTC.
Do you know of any, or can you recommend a BETTER compound, and vendor).
Many thanks as always.