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Standard troubleshooting 101: Do a careful visual inspection. Of everything. Reseat everything you can -- ROM, RAM, connectors. Measure the supply voltages.

You can indeed do a basic test with an ohmmeter. See the Classic Mac Repair Guide for the details. That said, the probability of the flyback being the problem is somewhat low. It's not zero, but the current-limiting circuits in the power supply should act to prevent drawing enough primary...

The repair guide has information you might find useful. See the stickie.

If you're worried, then practice first. If you're like most people, you've got some junk electronics lying about. Practice on them. There are many online tutorials on how to solder, so you can learn the basics first that way. Once you've built up some confidence, go for it. Use fresh solder...

Thanks, trag, and thanks, Wally!

The problem isn't so much with the cores themselves (they don't seem to get appreciably more brittle with time -- at least, in my experience). The main problem seems to be that they bind against the inside of the coil form (Wally notes that the teflon-like tape had degraded in the specimen he...

Thanks for undertaking this project, trag. I'm very interested in what you find out! I'm also interested in the measurements that you mentioned (the ones that wally may have made). Wally is an extremely careful, excellent engineer, so I trust his data.

See the schematic in the compact mac repair guide. It's all there.

Don't worry about the checkerboard pattern if it always goes away. Unlike later models, the Plus analog board doesn't have a congenital problem with caps, so this recapping business is not the first thing to consider here. The memory test is indeed causing the extended boot time. If you're...

Very common problem. Either the yoke connector needs to be resoldered, or C1 is dead. Even if it's C1, resolder the yoke connector anyway. See http://68kmla.org/files/classicmac2.pdf

The Mac Plus does not suffer from the capacitor rot problem that afflicts later models. You've got a loose connection somewhere, so that's what you should be focused on. Did you re-solder the yoke connector? That's the most common cause of the "it gets better temporarily when I whack the Mac"...

Here's a possibility to consider. Get yourself a low-profile 40-pin header, solder it directly to the NCR5380 SCSI chip. Then take a SCSI ribbon cable with connector on one end and solder the wires on the other end to the header. I did this 25 years ago, so I no longer remember if I had to use a...

The SMD decoder ring says that "KW" is shorthand for a 13V zener diode. Based on that value, and the diode's proximity to the power jack, my guess is that the diode is there for protection from reversed power connections and overvoltages. If the cathode (banded) end is connected to the positive...

A floating supply isn't necessary if you have a negative-output supply -- just connect the external PS ground to the PB's ground, and you'll be fine. Or rig up a few batteries (say, a couple of 9V batteries and a couple of AA cells, say). If adding the substitute supply causes an image to be...

Try measuring the voltage across the cap to see if you are getting the -21V bias. You should see this voltage at one of the connector pins as well. If you don't see it, that's your problem, and C22 is a likely culprit. I recall DigiKey having suitable replacements. But before bothering to hunt...

I believe that there is also a flex cable that connects the internal cage connector to the motherboard. It can get bumped loose, so check that it's properly seated. Maybe you'll get lucky!

Check for bent/broken pins on the internal connector. This is a surprisingly common problem. There might also be a fuse for the airport card (I don't remember for sure); if so, check it for continuity.

Just try it and see what happens. As long as you don't push too hard, you won't hurt the screen. I had a hot pixel in my first 3400c and the massage technique fixed it.

Another limitation of wannabe is that it does not run on 68000 Macs ("68K" does not automatically include the 68000, sadly). Loband on the Plus looks mighty attractive. I'm not near a Plus at the moment; would someone like to give it a shot and report back?

To the best of my knowledge, the two sets of coils should indeed show no continuity with each other, so it does sound as if there's a short somewhere. Yours would be the first shorted classic Mac deflection coil I can recall, so, um, congratulations. ;) (I'm assuming that the resistance...