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HP Pavillion S3123W

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Hi all,

My daughter asked me to look at her computer and at first the unit would not power up at all. There was a led in the power supply that illuminated but nothing occured when power switch enaged.

I disassembled the power supply and found one electrolytic cap open and others that were swelled and high resistance with cap wizard. I replaced 6 caps and I assume they were for the 5 volt side as they were all rated at 1000uf 10v.

After reassembly the unit fired up booted and worked fine for about a week. Now the power button illuminates, the ps fan, cpu fan and dvd door operate. There is no power to the keyboard, the monitor displays check input and it appears the unit is not booting. I cannot get anything to display on the monitor when attempting to boot to bios.

I suspect mother board but unsure if something else on the ps might have failed.

Any help in troubleshooting would be appreciated.

Thanks. Rfranzk.


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HP specs their PCs then lets the lowest bidder build them. At least that is what I heard. I have one sitting here that had a bad PSU. I found a new replacement on Ebay and it lasted about 2 months.

I would give that PSU another look. Is the 5V still 5V and what about the others. Look at them with a scope if you have one or can get one to use.


Thanks for the quick reply 3v0,

I will have to dig my scope out but did a couple of quick checks with a dmm. Black to red wires are 5.1v Black to yellow is 11.99v and Black to orange is 3.3v. I think that should be close enough to work??

I will dig out the scope and recheck probably not until this weekend.

Just found a new symptom. If the unit is unplugged or power disconnected for more than a few seconds, when plugged back in automatically powers up without touching power switch. Can power off with the switch and as long as unit is not unplugged will stay off. When plugged back in unit powers up. If i disconnect the switch wires from the mother board the unit will not power up.

Thanks. Rfranzk
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Hello All,

Wow, it was August when I last looked at this!! I recently had time to dig into this again and found all power supply voltages to be good. I found the problem to be a motherboard issue. I found a reman on E-bay and all is well now. I am curious if anyone has ideas on troubleshooting the old board. I found and replaced a number of capacitors with no change in function. There is no evidence of components overheating and no visible cracks in solder that I can see. Is this possibly a candidate for the toaster oven reheat???

Thanks for all the input thus far.

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