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@jajan547 : I've looked at the vias connecting C12 to R43/R44 (and on back to pin 10 of the PSU connector). Everything looks good and ohms correctly. I have cleaned out and re-soldered the via for C12 using a bit of fine wire to ensure connectivity on each side. @retr01 : Yes, I've checked...

Okay, I have another IIci logic board that turns on by itself and will not turn off via software. I have built a PSU extension cable so I am finally able to make measurements on the power on circuitry. As far as turn-on goes, on a known good logic board with the PSU plugged in UE13 pins 1...

Thanks for the great info! I had no idea how the system shut itself down. I spent a couple of hours last night and then a few more today verifying what I had measured last night. I have continuity from UB13 pin 1 to UE9 pin 60 measuring directly from pin to pin on the two chips. That tells...

Awesome, thank you so much! My wife and I are heading out to dinner and a movie (Top Gun) so I can't look at it right now, but I will later this evening. This schematic is much more readable than the Bomarc one, thanks!

Well, I replaced both UD13 and UB13 as well as painting all of the traces going underneath the chips with UV solder mask. No joy. I am really lost on this one, no idea how to go forward. I've ohmed between S1 and UE13/UD13 and everything looks good. Still, you can push that switch all day...

In my experience, just strong hot sunlight works very well with the beige Macs. I would not use the peroxide creme as it is the most prone to streaking and blooming unless you're very careful. I've used 40 vol liquid peroxide from Sally Beauty Supply mixed in a tub of hot water out in the...

I was an electronics technician in the Air Force back in the day, but it had been a long time since I'd done any electronics repair work when I became interested in retro computers a few years ago and began buying them to enjoy. I started with Ataris because that's what I had back in the 80's...

This is the one that I bought. It was a 3-pack so I have two left if you need one. PM me your contact info and I'll mail one to you. You'll need the wires and plug from the old battery pack so you can connect the new battery pack.

Great idea, thanks. I have one on order now.

@Volvo242GT: The CF to IDE adapter I'd ordered arrived today and it ID'd and formatted with an old 4GB CF card right away. I have OS 8.6 installed on the CF drive and the computer working perfectly. Well, except for the battery. I have to source a replacement for that. I got Doom and Doom...

The only jumper on the HDD is the CS/Slave/Master jumper. I've tried it in CS and Master with no good result. I have a G4 iMac I might be able to test the drive on. We'll see. It's interesting to me that the computer has an IDE HDD, but still has an SCSI bus that is used by the CD ROM drive...

My thanks to both of you for the help. I was able to download an ISO of OS 9.04 and burn it to CD. I can boot the CD on the Power Mac, but when I run Drive Setup it doesn't see the 250GB IDE drive, just the SCSI OS 9 drive. I don't know what to do at this point, maybe the drive is bad? It's...

Hi everyone, glad to be here! I broke down last week and bought a (doubtless) over-priced Power Mac 6500/250 on eBay. It looked to be dirty (expected), but in decent condition. The description said "no HD," and when I received it today that was indeed true. It chimes and boots, but sits at...

Very nice, the original 520ST machines are my favorite in the ST line. Hopefully the RAM upgrade is still working. I'm trying to figure out why a 1040 is missing the chips, caps and resistors for the 2nd bank of RAM. It probably really is only 512K, regardless of the motherboard silkscreen...