Aug. 14, 2007
Ok, This ain't a pinball machine... BUT it really got my goat.
I bought 4 Dell Optiplex GX1 computers at the computer show last year. Actually, the guy gave them to me. I wanted them for MAME machines. All 4 worked and I used one to convert a cocktail table. While doing the conversion, however, 2 power supplies died. Each time I simply cracked the case from one of the 4 and 'borrowed' it.
Ok - it's almost a year later. I checked to see if I could replace the supplies because I needed the machines for another project. It seems DELL uses a proprietary non ATX standard power supply. Ok, great, I can buy them on Ebay for about $10 + shipping. But NOOOooooo. I have to fix these, being the frugal guy I am...
The power supplies will not come on and have no 5v standby supply. There's almost NO reference on the web for these and no schematics. After a few Buds I decided to pursue the repair. Note: I have many years experience repairing switch mode power supplies - yeah, I know what you're thinking - Bud and 230v line derived DC don't mix and you're right!
In any case I was able to manually eyeball the problem to open 510k resistors in the power supply. R110 opens and doesn't supply the standby circuit. It just so happens I had a scrap RCA TV chassis and pulled a 100k ( closes as I had ) resistor and simply piggy backed it to keep from disassembling the entire supply. Actually, since there were two supplies, the first one was completely disassembled but the 2nd one is always easier.
Ok, now you're going to laugh because of the reason for digging out these PCs... My HULK pinball lasted a couple of weeks and blew the sound board. Troubleshooting lead to the irreplaceable 6530 RIOT chip. Replacement boards cost money. The Optiplex cost $0. I decided I'd like to program a cool sound scheme for the HULK using a PC which is cheaper than a chime box or new audio board.
In short: check R110 on the HOT side of the supply and/or replace as needed if you're Dell 145 SNF power supply is dead and has no 5v standby.
TIME: 5 minutes if you just piggy back it.
Notes: 5 volt standby is located on the purple wire. The DELL ATX supply is NOT the same as a standard ATX power supply so wire colors and pins don't match up.
Warnings: Switch mode power supplies can kill you if you don't know what you're doing.