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Need help with new psu for a PC, no monitor signal

Submitted by MaxTek on March 27, 2008 - 11:29pm. Other Computers

I have a Compaq presario and sold the original power supply to a client for their pc. Now I have a need to use this Compaq. I bought a Compaq 300w power supply (new) from Ebay.

I hooked everything up and can't get anything to the monitor. It shows "no computer signal".

The power supply is an ATX with the additional connector (12V header, a 4 pin connector arranged as a square 2x2) but my motherboard DOES NOT have the outlet for this additional 2x2 square connector.

Is that the culprit? Do I need another power supply that doesn't have this additional connector?

Thanks.

MaxTek

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eeun's picture

I take it you're still gettin

Submitted by eeun on March 28, 2008 - 12:55am.

I take it you're still getting some sort of start-up; fans, beep... but without video?

Compaq, like Apple, has had a habit of using nearly but not quite ATX connections. If the pin configuration has changed, there may no longer be power going to the AGP (or whatever you've got) portion of the motherboard.

Trick is find your Compaq model number's PSU pinout, then modify your current PSU to match.

...that is all assuming your new PSU is working properly.

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MaxTek's picture

Re: I take it you're still gettin

Submitted by MaxTek on March 28, 2008 - 11:35am.
eeun wrote:
I take it you're still getting some sort of start-up; fans, beep... but without video?

Compaq, like Apple, has had a habit of using nearly but not quite ATX connections. If the pin configuration has changed, there may no longer be power going to the AGP (or whatever you've got) portion of the motherboard.

Trick is find your Compaq model number's PSU pinout, then modify your current PSU to match.

...that is all assuming your new PSU is working properly.

Startup, hard drive spinning, fans etc but no beeps. This morning I found a site that stated the psu with the square 4 pin molex connector is for pentium 4s. My Compaq is a AMD. So I guess I have to find an older psu.

Thanks for the helps

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coius's picture

4-pins

Submitted by coius on March 28, 2008 - 12:40pm.

The 4-pins was also used with AMD. it's just and extra 12v Connection for the CPU. It will work fine. Have you switched monitors?

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coius's picture

just want to add

Submitted by coius on March 28, 2008 - 12:42pm.

you don't need the extra 4-pins for the system to work. Can you try getting another video card? PCI? AGP? PCI-Express?

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eeun's picture

Coius, I think the problem he

Submitted by eeun on March 28, 2008 - 3:14pm.

Coius, I think the problem here is Compaq has varied its pinouts over the years, even though the physical connector has stayed the same.
It may be the new PSU is ATX, but the older motherboard is not. Or neither may be true ATX.
Without determining that first, IMHO it's pointless to start component swapping.

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MaxTek's picture

Re: Coius, I think the problem he

Submitted by MaxTek on March 28, 2008 - 8:45pm.
eeun wrote:
Coius, I think the problem here is Compaq has varied its pinouts over the years, even though the physical connector has stayed the same.
It may be the new PSU is ATX, but the older motherboard is not. Or neither may be true ATX.
Without determining that first, IMHO it's pointless to start component swapping.

How do I determin this? The PSU and motherboard obviously have the matching ATX connector. The motherboard has a blank space where the square 4 pin connector would've gone.

I know the video card that is in there works because it did when I removed the original PSU and sold it.

and yes I have tried two different (know good) vga monitors.

Thanks.

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eeun's picture

I'd start by Googling your Co

Submitted by eeun on March 28, 2008 - 8:56pm.

I'd start by Googling your Compaq's model #, and see if you can find PSU part number, pinout.
You might get a pinout for the new PSU the same way - all Compaq parts have a model # - or by checking the PSU for pinout info, or using a multi-meter (which will only be partially useful if you can't get full power to it).

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