I'm going with you on this one. I know computers have a limited lifespan, and in fact I already got a replacement machine for exactly that reason. Repairing this was more for a hobby / interest. But eventually you end up trying this part and that part, replacing all the parts, and spending money, all on older compatible parts -- to where you would have been better off buying a new machine in the first place. I tried the thermal paste, but it did not help. I was tempted by a refurbished replacement mobo and CPU on ebay at only $40 -- but they will break soon anyways. Saturday afternoon is enough, and it was fun, but time to move on. EDIT -- 2 Saturdays, not one. Sorry, forgot to count last week. Thanks everyone for suggestions and help.
You never mentioned if you found if it was chip creep syndrome. I would not be surprised if that problem still exists.
Last week I tried: - remove memory, and try them one at a time, in a different slot from where they were at the beginning - removed video card and plug monitor directly into mobo VGA out - new SSD drive - replaced power supply with new one This week: - pulled out CPU and fan, resat CPU, applied thermal paste by the 'pea' method, reattached fan Chip creep I suppose could still be possible. There is a wireless network card plugged into PC1 slot, and landline modem card in PCIEX 1 slot, that I did not try removing. Also to mention -- I cleaned out all the dust really well. I have dust allergies, so I wanted to clear it out before working on the machine for a long time.
My bet would also be on the motherboard having a bad component. Likely candidates are capacitors on the board. Chips, including the CPU, don't suddenly have a failure when they are not powered. Chips which consume a substantial amount of power, like a CPU, have a temperature protection built in to prevent it from getting damaged due to overheating.
Agree with Morse... 10 years old, not worth trying to get it running again if other than simple fix. Wouldn't put any money into it at all. Recommend HP Z440 at Newegg. Any configuration you want. Currently starting @ $328.
See Bob? The other side of the coin: I had a computer built around 2003 with all the latest/greatest. Sped up the CPU and memory for $50 (delivered!) in 2011; bought 3 more years' service. Currently "driving" The Great White Horse (so named because of its enormous case) which is now about high/middle range of performance at 5 or 6 years old -- water-cooled 8 cores; multi-gig GPUs -- all that rot. Recently doubled its memory for $50 -- used to be ~$300. Still Windows 7 because, "Windows 7"..... (Might again return to the Linux fold because of that, although some reasonable people do seem to find Windows 10 'agreeable.') My point is, 9 computers in 18 years?!?!? You've made somebody a career! ((And, my vote is, the CPU.)) ((( And whether out of sequence or not, there are a lot of good PC tips on this thread -- a great read.)))
Better use a stop. Likely a loser... at least in terms of cost/value. (I also think mobo is likely candidate, but not worth the money to replace.)