Recent content by mchineboy

Success! Well almost success. Replaced all of the 253s and 257s. Nope. Replaced the BMU2 and TSM chips. BINGO! Now the only thing left is that startup sound is still the low frequency buzz which makes me think it might be something on the analogue board?

Thanks for the tips. I at least know where to start with the scope.

Welp. That wasn't it. Same issue persists. I'm going to replace the sockets next, but not until this evening.

@Builde68 You've nailed it. I hadn't considered the ROMs might be at fault. I pulled the ROMs and put them into my tester/ripper and the LO rom is testing bad! (As in completely unreadable) I've got two new 27C256 EEPROMs on the way and will burn some new copies this evening and report back...

The SIMs I have are the 8 chip 1mb. Only two so I'm putting them in the lower bank.

It's got 2 1mb 30 pin SIMs in it. Unfortunately I don't have any other 30 pin sims other than what's in my Iici. Edit: The resistor is clipped according to the documentation and I've confirmed that its not making contact.

I went ahead and reflowed all of the joints on the analog board with fresh solder. Same symptoms as before, no change.

I recently acquired a Macintosh Plus that I knew would need repairs. I have already rescued a 512k with success. At the start, it was clear that the Mac was unhappy. The symptoms as I received it are as follows: * The startup beep is a low frequency buzzing sound. The length of the beep is...

I'm working on a IIci as well. I had it working last night, then I tried to put the cache card back in and dead. Gone. No more power on. I think I'm looking for a "troubleshooting guide" that walks you through a series of "check this, then check that". Does such a guide exist?