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HP PC won't boot after installing new GPU

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Last response: in Systems
August 11, 2010 7:18:18 AM

After installing a GeForce 9800GT 1gb on my PC, the computer would crash soon after starting a game, and restart. After a few times of this ending with an abrupt blue screen and system shutdown, the PC will no longer boot.

Before this, had unsuccessfully tried to install a GTX 465 on this PC. Screen would display GPU information, then freeze at boot screen. After removing, was able to run system stably with 9400GT that I've had for about a year.

Clearing CMOS and removed GPU, started with only the factory installed 1gb RAM and stock 300w power supply. HDD is making boot up noises and CD drive has power, and Motherboard and CPU power pins have been plugged in and out firmly many times.

Two other potential issues. First, CPU heatsink was badly clogged with dust, but cleaned now. Also, for about a week I had 3GB of RAM from 2gb+1bg arrangement, but mobo max. allowed lists 2GB.

I've tried everything I could find in similar posts here and from other sites but I am out of ideas for what's going on with my PC.

HP SR2050NX Desktop
Mobo: RC410-M
CPU: Intel Pentium D 820S 2.8ghz dual-core 800mhz 775
Chipset: ATI Radeon Xpress 200
Memory: 2GB (2x1GB) PC2-4200 240-pin DDR2
PSU: 300w stock / Cooler Master GX-650W

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August 13, 2010 6:16:33 PM

That really doesn't tell you that much.

Oh, if it doesn't work, it tells you the PSU is either dead or it's not getting any power.

If it does work, all it tells you is the the PSU can produce enough current (less than 1 amp) to power a fan. It doesn't tell you anything about the 3.3 and 5 volt rails. And it doesn't tell you if the control signal called "PowerOK" that runs from the PSU to the motherboard is good.

A somewhat better (but still not foolproof) way to check a PSU:
Try to borrow a known good PSU. If you cannot do that, use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.

The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.

This checks the PSU under no load conditions, so it is not completely reliable. But if
it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU.