On the Bench

One of the things I do up here is run a computer repair business. Generally lots of fun but today is not a good example. I have a client with an old MAC computer -- not just any MAC but one of the licensed clones made by Power Computing. The top of the line PowerTower Pro. He came into a bit of $$$ back in 1990's and splurged on the best system available at that time. He brought it in with a dead power supply. I was able to find a new working exact replacement from these guys (story is here). Had some time today so started working on his system (he is on fixed income and specifically told me that it was OK to back-burner his machine -- it had been dead for a while). Tested the new supply -- worked fine, voltages on spec. Tested the old supply -- dead as a dodo. Put the new supply in, plugged it into the motherboard and pulled all of the PCI plugin cards -- it powered up for a second and then shut down. This means that the power supply is trying to provide the proper voltages but that the motherboard is not sending an OK signal back to the supply. Not a good thing. I started poking around and finally tested the CMOS battery (a 3-volt lithium cell). Zero volts. Hmmm... Pulled it to test it out of circuit and noticed something that gave me a sinking feeling in the pit of my stomach:

Note at the top picture, the little Plus indicator at the top of the battery. Note at the bottom picture, the Plus indicator embossed at the bottom of the battery holder. The inside of the case was fairly dusty (probably kept on the floor) but the area around the battery was clean. It looks like my client replaced the battery but put it in backwards. I will be trying the machine again later tonight with a couple of AA cells in a holder with test clips that I use for this purpose but my gut feeling is not a good one. I will be checking with ReLectronics next Tuesday to see if they have any Power Computing motherboards but I am not holding my breath. Fortunately, decent MACs of this vintage are often for sale for well under $100 so he can resuscitate his system in a new box but this is not what he will be wanting to hear...