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This is very interesting. I actually wondered about this when turning my early Mac II on, then immediately off. My IIx and IIfx will reliably turn off after a delay, but Mac II would just power-cycle instead. I actually thought I might have some power circuit issue.

I just searched my boxes of lose parts and I found a couple of those exact transceivers. You might find some used ones on eBay cheap, but it might be more cost effective to just buy a battery bombed board to steal them off of. There are probably multiple Macs that used that part. With that...

Just another follow-up. It looks like C7 must have been introducing some parasitic components (current/inductance?) to Nuchip and/or surrounding ICs. After rescanning, many of the pins that were previously showing some (minor) fluctuations are solid now. Here's an example of the first /START...

Machine is fully functional now! The culprit was a defective bus transceiver at C7. This was not obvious at all, and I'm actually surprised that I was able to track this down. All of the input/output pins, and control pins were sending/receiving signals, but the wave shapes on pins 13 and 14...

The Diimo 030 (the tall card built specifically for the SE/30) doesn’t need Twinspark and sits vertically. It’s my favorite card for these.

Looks like the grounding foil that’s normally attached to a small groove inside the back case. They are missing in most machines because they usually fall out first time the machine is opened and most people don’t know where they go.

If you're talking about the topmost corroded trace, it runs between the audio jack and pin 17 on UB11 (VIA 2). On the audio jack, there are two rows of 3 pins. So from the back of the board, it's the middle pin of the second row.

Double post.

Thanks, you saved me from spending the weekend barking up the wrong tree. Based on your advice, I probed for the interval between /START and /ACK. Without a video card, the delay was roughly 26 microseconds. With the card, the delay was only about 450 nanoseconds. So based on your info, that...

Hey all. I'm hoping someone can help me. I acquired a Mac IIx, did the standard recap and repaired some traces, pretty standard work. However, the NUBUS is not working. The machine is otherwise healthy, boots to floppy and SCSI, responds to ADB, etc. I checked traces and everything seems...

Not familiar with the TAM circuitry, but that blown tantalum can be causing a short. I would definitely remove/replace it before doing anything else. Also, I would check the ferrite bead next to it at L4 for continuity.

I believe 24-bit is always in color, i.e. there isn't a setting for millions of grays. So the control panel just automatically assumes it will be color.

So it’s a bit inconsistent. I was able to reproduce a similar issue in 256 color mode, only with a very specific desktop pattern. So it's not just black and white. But other than that specific case, the artifacts are gone in 4/16/256/millions of colors. Solid black or solid white desktop...

Hey all, One of my 8.24 GCs has this odd behavior. In black and white mode, it has these faint blue vertical lines. They disappear when I use higher color modes. Any idea how to troubleshoot this? I don't see any physical damage and most of the components look fine. I tried reflowing the...

Goodness (drool)! I wonder how much this would have cost back in the day.

Ahh, thanks for the explanation. It makes sense, and honestly I always wondered why the SWIM chip plays a role in memory addressing. I think the confusion is that some of the literature refers to it as the "SWIM upgrade", which includes the IIx ROMs. So, PMMU alone gives you 68MB, and ROMs...

As far as I know, the Mac II with a ROM upgrade is still dirty and requires Mode32 regardless. Coupled with the PMMU, it allows the machine to address up to 68MB or RAM. I.e. you need both upgrades to address more than 8MB. I believe you additionally need the SWIM upgrade to get 128MB...

Honestly, even if for some reason the spacing is wrong, I would just cut them apart. The single slots from PE are much more expensive.

Those should work. I used them on a different mac (LCII?) and they were a perfect replacement. I believe all Macs, including the Mac II, have the same spacing on their dual 30 pin slots. PE is probably the best vendor for these parts.

Oh, right, bad example. I was mainly referring to the Mac II series (last paragraph). I think I found the benchmark thread I was referring to: https://68kmla.org/bb/index.php?threads/fastest-nubus-video-card-redux.42495/