Hi there,
I have a formerly working Mac II that was stored for a few years and when retrieved would not turn on again. I became aware of the PRAM battery situation and around here was only able to get my hands on 3.6V 1/2 AA batteries rather than the 3V soldered to the motherboard. Anyway, I tried connecting them anyway (they have the little pieces of wire soldered to each end, so I soldered them to the remains of the old wire I'd clipped the old batteries from. I've confirmed voltage is getting to those wires and thus the mainboard, but neither by switch nor by the keyboard would the machine power up.
I then took a third battery I had and did the jumpstart procedure to the white wire on the PSU connector. Sure enough, the PSU fired up, but there is no Mac chime, and the second the battery is removed, the PSU shuts off. Holding it in place for a while produces no activity.
I've pulled the board and inspected it.. it is in excellent, clean condition. I don't see any evidence of cap leakage anywhere and the traces all look good. Wondering where I can go from here?
Any assistance would be greatly appreciated!!
On Asimov FTP you'll find an archive called Apple Service Technical Procedures - Macintosh Family_PN072-0228.zip. This also covers Macintosh II.
Find it here: Link.
In this large zip (1.4 GB) there is a PDF called PN 072-0228 - Macintosh Family - Volume 2.pdf, there you will find help starting at page 157.
Do you have a meter to test the "new" battery voltages to be sure you're really getting > +3V?
I'd also test the PSU voltages as well. Startup without chime could be bad caps, bad ram, probably a few other things too.
I checked the battery but not the PSU... I was trying to figure out how I'd get it to come on and stay on while I tested the pins to see what it was putting out. I wouldn't be surprised if it's the PSU. The rest of the machine is in excellent physical condition.