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If you didn't recondition the analog board, stop until that's done. Save yourself a lot of ghost-chasing.

The reason to do it is that the Ethernet specification explicitly calls for 60 seconds of isolation protection to 1500Vrms @ 50-60Hz.

They are, and you are correct.

Oh... actually, wait a second. It could be ringing, but usually you'll see more than one "echo". It just occurred to me that I've seen a very similar display fault with a sync-on-green Mac display card, when I've had the separate sync lines (Vsync + Hsync) connected at the same time. If your...

That "shadow" is called "ringing", and it's what happens if you don't terminate your transmission lines correctly, have impedance mismatches, or a variety of other wiring faults. I'm inclined to suspect your "hacked together adapter" is at fault. How did you create it? One other possibility...

Same one. The project was always to restore this microExplorer. I have another II that needed attention, but its problems were much more straightforward and were solved relatively quickly. Now if I could just solve the apparent address/data line problem that's preventing this IIx from...

Myriad. To start, the batteries were dead. They were replaced. All of the 47µF SMD electrolytics were replaced. The trace between R3 and C6 was repaired. All of the axial electrolytics were (unnecessarily) replaced. The Sony sound chips were (unnecessarily) replaced (and socketed), though...

Here are the final results of the restoration effort.

That is basically the solution. Use polyester, metallized poly, or mylar caps. They're all essentially the same, for this application.

The DP83932 is an ordinary Ethernet PHY. NatSemi made them, TI made them... I'm sure there were literally dozens of PC ethernet cards based around this chip, also.

Here is the answer to the riddle: The trace between the + side of C14 and pin 10 of UI14 (the Sony sound chip closer to the MC68020) had come open. I repaired it and the II lives. Or at least, gives me death chimes, which is expected since I have no RAM in it while it's on the bench. (The next...

ISTR that when I traced it out, R3 was still connected to R18, but neither were connected to C6. My first repair simply put a long piece of bus wire between the appropriate sides of R3 and C6. As you noticed, they are on different sides of the board, so it is ugly. I put some effort into this...

Somehow a trace involved in the connection between R3 and C6 comes open, which prevents the power switch from turning on the machine. I'm not sure about "common", but it has happened on both my IIs and my IIx. I'm not sure how it happens, or exactly where on the board it's going bad, but it's...

Your understanding of the soft power circuit matches mine. The reset circuit would need the clock, though, as I understand it counts clock pulses to accomplish the correct delay between power-on and starting the CPU.

Hm, clock. That's an interesting thought; one of the leaky caps is near the crystals, and they are sensitive to stray capacitance (like from leaked electrolyte). A failed clock could certainly produce this failure mode.

There's a little more to a reset circuit than that. RESET is held low during power up; it's the RESET circuit that is responsible for bringing it high at the right time. For example, I had a SonicBlaster that would cause a IIgs to not boot, and it was because a 74LS series chip had failed in...

Yes, of course they had leaked (not the batteries I mean). That is why I cleaned the board twice. This is the part I am new to, and may not have gotten the art of yet. I understand others have brought boards back to life by cleaning them and wouldn't mind some advice from those who have...

Well, perhaps. But the ROM chips play no part that I can tell in the reset circuit. Reset has to come high before the CPU can execute any code out of the ROMs.

Folks; I have been working on bringing an old Macintosh II back to life. I'm not new to the process, but this one is stumping me. replaced both batteries replaced all the 47uF SMT caps replaced all the radial electrolytics for good measure repaired a failed trace in the power circuit...

Esteemed folks; I recently acquired a IIci in a load of other Apple gear. It had been a developer's primary desktop for many years before it was shut off and stored. When I powered it up, it came up to a straight grey screen (well, after I replaced the battery, anyway). No chimes, but a recap...