Early last year, I bought a very nice 1999 Gateway GP7-500 PC and matching EV700 17″ VGA CRT display from someone fairly local who got in touch with me via my website. This had been plugged in on a desk in his loft since he got it back in 1999 along with the rest of the original setup including speakers and fax machine, so was a pretty neat time capsule.
The GP7-500 has a slot 1 Intel Pentium III @ 500MHz, 128MB RAM, 3DFX VOODOO3 2000 8MB AGP graphics card (210-0364-003), Creative Sound Blaster CT5803 sound card, Lucent 56K PCI fax modem, and 80GB Maxtor IDE HDD – a pretty powerful home system for the time! The computer even came with its matching keyboard, mouse, user manuals, and system disks, and even a cool set of period Cambridge Audio speakers.
Apparently it all still worked, which is neat for how long it had been sat. I picked them up in January 2025 and they sat for quite a while until December 2025 when I had enough time and interest to clean them up and try them out.
I cleaned the inside of the PC out pretty thoroughly as I was interested to see what was inside and make sure that nothing was awry (i.e. bulging electrolytic capacitors on the mainboard), and everything looked OK. I plugged it in and tried powering it up, but unfortunately there was no response from the power button, the PC was dead.
I checked the power switch connections to the mainboard as well as the power switch itself, and these seemed OK – I tried powering the PC up from a known-good 500W ATX PSU and it did pass POST, so the original PSU was at fault.
I thought this wouldn’t be a problem and that I could just swap in a more modern ATX PSU, but unfortunately the original PSU (Newton Power NPS-200PB-96 200W 20-pin ATX v1.x) is not a standard size, has a -5Vdc supply which is missing from a lot of modern PSUs, and also has a fan and shroud to help cool the Pentium III CPU, so it’s not that easy.
I tested the PSU using my ThermalTake Dr. Power III ATX PSU tester, and it was completely dead – ATX PSUs are supposed to supply a 5V standby (5vsb) supply all the time so the mainboard can power the system up, but this supply seemed to be missing as the tester didn’t even power on. This is usually a smaller standalone switching PSU separate from the main PSU, which could never be powered on without it.
The PSU was easy enough to dismantle for inspection – other than being pretty dirty, there was nothing obviously wrong (bulging electrolytic capacitors, blown fuses, burning or scorching to the PCB, etc). The fuse, mains input, and bridge rectifier seemed OK as high-voltage (approx. 330Vdc) was present across the two bulk capacitors.
I removed and tested all of the electrolytic capacitors to check for physical leakage and ESR using my Peak ESR70 and all of them seemed OK – it’s common for the output smoothing capacitors to fail as they work pretty hard, and for the smaller decoupling capacitors for the control IC supplies to fail as they’re more susceptible to getting baked out. Thermistor TH951 on the heatsink with the output rectifiers seemed OK (approx. 5kR cold), which is probably used for temperature feedback and could cause problems if open; all the big diodes / rectifiers / FETs seemed to test OK in-circuit, some showed as a DC short because they’re connected across transformer windings.
The area which seems to be for the standby circuit around D501 (1N4005) was pretty discoloured from heat, but the diode tested OK in-circuit; Q902 next to it (ST D1NA60-1) got up to about 60C so I removed and tested it but it seemed OK, the part is rated to run pretty hot; the 2N2222A transistor nearby also tested OK.
I went around the standby circuit checking for short-circuits, and found that the 1.2MR (1W?) power resistor at R904 had failed open-circuit. The resistor didn’t have any visible external damage and didn’t seem fusible, it’s possible that it wasn’t rated for enough power and burnt out by being left plugged in for so long.
I replaced this with two 1W resistors (1MR and 200kR) in series as I didn’t have a 1.2MR part, then powered up the PSU – the 5Vsb supply now measured about 5.2Vdc whenever the PSU was plugged in, which was a good sign that the standby supply was now working.
I connected up my PSU tester and it now seemed to power on, another good sign that the standby supply was now working OK – I tried using it to power on and test the PSU but it wouldn’t start up properly, showing some voltage and immediately powering off, not giving a “power good” signal – this was without any other load, not even the cooling fan.
Some older switching power supplies like this one can be a bit tricky when they don’t have any load connected, a load is often needed to properly regulate the main supplies – I connected up an old 3.5″ IDE HDD in case the PSU tester was not providing enough load, and sure enough the PSU now started up and tested OK.
I cleaned and reassembled it, then reinstalled it into the PC.
With the PSU reinstalled, the PC and CRT combo seem to work great! The original CMOS battery was understandably dead so I fitted a new CR2032 cell and reset the BIOS settings. The PC has a copy of Windows 98 installed, I plan on imaging the original HDD then installing my own stuff and having a play around, maybe fitting an IDE SSD or CF card – it’s got quite a capable graphics and sound card so will be good for some retro gaming.
