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If you look carefully, you will see that both vertical and horizontal dimensions are affected, not just horizontal, and only slightly (10% is not a huge variation). That's an important clue. Your problem may be no more complex than the yoke not being mounted flush against the crt. Take a careful...

Reversing the polarity on L3 cannot have any effect if C1 is truly healthy, since the job of C1 is to block dc. If there's no dc, then L3 behaves the same regardless of which way it's inserted. Since you replaced C1 with a high-voltage cap, I'm inclined to absolve the capacitor of any role in...

Yes, exactly. It's so easy to do it right that there isn't any justification for trying the wrong way just to see what happens. Applying power backwards to semiconductors rarely results in a happy outcome...

Note that Dan is a digital engineer. He has clearly not run many (or any) experiments, and is just voicing an opinion. He would not get a good grade in my circuits classes. His answer about the "heavier gauge wire" is utter nonsense. The currents flowing (both signal and power) are so small that...

No, not static electricity. As techknight says, you were lucky, plain and simple. You shouldn't assume that everyone else would be as lucky as you.

That's also a first for me. Thanks for the pic. I'll have to open a few units and see how common this is/was.

If the logic board is drawing enough excess current to pull the 5V line low, something on it should be getting decently warm. With care, you should be able to find it. The area between your upper lip and nose is particularly sensitive, so if you don't own a thermal imager, that's not a bad...

There's all kinds of misinformation and downright nonsense in some of the posts here. Current through the heart is indeed an important consideration. But comments like "It takes X volts at Y amperes to kill you" make no sense at all. Current and voltage are related by Ohm's law -- your body is...

I second that recommendation. Poly over paper. Always.

I know the author quite well, and he proudly admits to laziness. :)

The Classic Mac Repair Guide has a verbal description of how to put one together. Sorry that it doesn't have a schematic -- the author was a very lazy fellow.

The output can also drive some modern monitors (not all can handle the low resolution, but many can). I homebrewed an equivalent interface module back in the day, to drive a large monitor. You haven't lived until you've seen System 6.0.8 on a 21" CRT!

You might find the Compact Mac Repair Guide of some use in debugging your classic. It's among the Stickies, above.

Don't forget J1. It causes trouble more often than the flyback joints. Check C1 while you're at it. (And again, for details see the compact mac repair guide among the stickies.)

There are several joints that frequently cause trouble in the classic Macs. See the repair guide among the stickies for details. Good luck!

Without a more detailed description, it's hard to say exactly what's wrong. But large focus variations across the screen are rare without an accompanying symptom, such as incorrect raster size (or symmetry problems), or a brightness problem. If the brightness is set too high, focus variations...

You are seeing 170 across the primary cap, so we'll assume that all is ok there for now. In general, testing of components should be done out of circuit because there can be many sneak paths that can confound measurements, as you've found. In-circuit testing is an iffy proposition. Interpreting...

Don't do that -- use test equipment and logic to narrow down the suspects. Judicious use of an ohmmeter will get you very far, so you don't need very sophisticated equipment for the majority of problems. Did you check the SCR, for example? It frequently is destroyed by other faults with the...

Sounds like you've made a lot of progress -- congrats! The only other cap I'd bother with on the analog board is C1. If the others look ok, you can probably leave them be. Once you get the thing to power up, you'll be in a better position to evaluate what other steps (if any) you need to take...

Yup, exactly. The "chopper" device in the classic macs is Q11 in the Repair Guide. The SCR often goes south along with Q11, which is why it's mentioned. But Q11 should definitely be checked, as you advise. Q9, too, is frequently a victim.