PSU and fried mobo/cpu question

whatmeworry · October 8th, 2003, 02:43 AM

I had a computer that was running a long time on a bad 350 W PSU brought in for repairs. When I changed the PSU to a 500 W PowMax there was a pop and smoke from a circuit on the mobo. The CPU also has burns on the L1 and L2 caches (by all the dots).

Is this a result of pre-existing damage or could the new PSU have caused this?

What sort of retailer would carry PSU testers? I need to replace the computer by friday and do not have time to wait for online delivery. I live in Queens, NYC, would staples have something like this?

Sorry for all the questions

Chuckiechan · October 10th, 2003, 11:27 AM

I think you should be able to test it with a volt meter. The voltages are usually printed on the side of the PSU. I think to do that tho, you need a "load" hooked up like maybe a hdd or play a music CD.

Try searching this board for "testing" and maybe try "PSU" , or "voltages".

I would return the PSU just to be safe and by a known brand, and put in a new MB and be done with it. It sounds like to board is a gonner anyway, and I'd not want to blow a new board with a defective PSU.

dafanman · October 10th, 2003, 12:51 PM

whatmeworry,
I just saw mention of this the other day, If you do a google search for powmax youre gonna get some links related to powmax psu burn out.

Good luck

Bovon · October 10th, 2003, 01:04 PM

All computer power supplies have the same output voltages. AT has one setup and ATX has the most recent. If the powersupply caused problems on the motherboard and elsewhere, I would suspect the regulator in the psu was not working properly and the voltages present were higher than they should have been.

You might be able to get a tv service technician to test the voltages if a tester cannot be found locally, but a tv technician would not know how to connect an ATX psu, turn it on, then know what voltages should be present.

Uncle Bob · October 10th, 2003, 01:30 PM

Compusa carries psu testors .

dunbar · October 10th, 2003, 02:07 PM

Sorry I missed this post...
Pre-existing, IMO, but you can't tell where all the overcurrent started from, so other things might be fried - Hard disks, CDRWs, etc.

Each output is not individually regulated for voltage and current regulation, no matter what these posts may say - my 20 years as a PSU design tech tells me this.

The new 500W PSU had the 'strength' to blow out the stuff, whereas the older PSU simply did not have the meat to do so.

Despite having similar voltages, the overcurrent protection settings can vary widely. If something in the PC (not just the mobo), wants to draw a otal of 12 amps on a 12 volt output, 200W PSUs usually collapse the 12 output, dropping to something considerably lower than 12 volts, because the 12 volt outputs are not usually very strong on 200W PSUs. That means 12 amps times the low voltage is low wattage, which = limited heating.

When the new PSU was hooked up, its extra amperage ability implies that the 12 volt output was able to pump up the voltage to a higher amount on that 12 volt line, now the 12 amps is at some postulated higher voltage at 12 amps.... generates enough power to develope a lot of heat, heat = poof.

CompUSA PSU testers cannot do everything necessary - dedicated PSU test systems still cost thousands of dollars (if not tens of thousands) for limited testing capabilities.

ArcticFox · October 12th, 2003, 08:20 PM

Yep, looks like you wasted your money on a throwaway power supply. Replace it with an Antec, Enermax, Thermaltake, or PC Power&Cooling which are made well and won't burn up on you.