Thanks again to Stephen for sending me a set of replacement ROMs (completely free!). I have 7 compact Macs of various types, but one of them has never worked since I received it -- a Mac Plus. I was able to confirm that the ROMs were the culprit a while back by swapping in some known good chips...
I found a "Mac Bottom" on eBay recently for a fairly reasonable price. I don't have an external SCSI hard disk, so I thought I would take a chance on it, even though the seller didn't really seem to know whether or not it worked. When it arrived, the fan inside had broken free of its moorings...
I'm not very knowledgeable about capacitors, but here are some photos of my boards if it will be helpful (I also have one more that I can't find at the moment). One of mine is a Japanese board and one is American. I don't see anything else that looks like a capacitor to me.
I did try swapping the RAM earlier but neglected to mention it. But I've never taken out a Mac's ROM chip (and wasn't even sure if they were socketed until I checked which ones they were). After doing some swapping around of chips, I can say that it is definitely the ROMs that are at fault. When...
How did this work out for you? I’m wondering if a problem I’m having with two of my Mac Plus units might not be related to the ROM since the symptoms seem similar and I’ve narrowed it down to a logic board issue.
I don’t think I actually tried it before, but yes the logic board from the good machine does work in the bad machine, so it does look to be a logic board issue. I haven’t tested voltages because I don’t really know how, although I do have a multimeter.
I guess what I want to know is if...