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After reflecting on your friends' theories a bit further, I think I've figured out what they were thinking. It seems that I've overlooked the possibility of a mismatch in relative humidity specs. If the Aquadag formulations are designed for different RH, then there can be a large fluctuation in...

You can probably skip the solder-sucking step and go straight to resoldering (with fresh solder). There aren't that many joints, so you can refresh all of the usual suspects in a short time. Just work carefully, and inspect along the way, to make sure that you have not created solder bridges. If...

Hate to sound like a broken record, but you have a bad connection or three. It's really that simple. You seem to want to believe it's something else, but everything you've described is consistent with that hypothesis, and pretty inconsistent with any other likely scenario.

For turning the ferrite cores inside inductors, one generally should use a nonconductive tool. This recommendation becomes a mandate for inductors used in horizontal deflection circuits. So, even if you find a hex wrench that fits, you will find that the mere insertion of the tool into the core...

Your physics teacher's hypothesis makes no sense. He may be a good high school physics teacher, but he clearly knows next to nothing about the physics of CRTs, if he's talking about "imbalances" and "voltage fluctuations" as having any relation to CRT voltage ratings. In trying to make sense out...

500MB is no problem. Depending on OS version, there can be a partition size limit, but you are nowhere near any of them at 500MB. For all of the gory details, see http://support.apple.com/kb/TA28860?viewlocale=en_US

In general, it's hard to perform reliable in-circuit testing of caps with ordinary instruments (eg, the trusty multimeter) because so many other circuit elements could present sneak current paths and confound the measurement. Fortunately, many failures are sufficiently dramatic that you can...

All the circuitry downstream of the power supply is the same for 240V as for 120V versions, so you won't have to hunt down a special flyback (if that turns out to be the problem). I'm still a bit concerned about the capacitors. They're well sealed and designed to take full line voltage (and...

Wow -- C33 blew? That's the first instance I can recall of that one going south. I'm sure you've already checked, but you're not powering up a 120V Mac with 240V, by any chance? The Plus does not have a universal switcher, so bad things will happen if it is supplied off of twice the mains...

It sounds as if you've done the straightforward, logical first checks, so it's time to peel back more layers of the onion ("when you've shed enough tears, you'll be done"). It's not a bad idea to check the flyback -- instructions for doing so are given in that same document. The common failure...

The issue is one of providing information to the OP so that he can get his Mac fixed. The information I gave is correct: There is no incompatibility between the Plus and SE CRTs and yokes at all. He can swap them freely without worries. That's the only information he needed. Your post muddied...

Don't worry about interceptor2's comments about capacitances, glue and such; they are irrelevant for your compact Macs. The yoke (not "yolk") is gently fixed in place by a weak glue. If you need to remove the yoke, it's not hard to do so, and it's perfectly legitimate to remove the yoke...

Instructions for discharging the crt are in the document I linked to earlier. There's even a photo showing the proper discharge location, as Osgeld alluded to. No special tool is needed. Don't even bother with a current-limiting resistor -- online advice about this is simply wrong (high-voltage...

The yokes are fully compatible between the Plus and SE, mechanically, electrically, and pin-connection-wise. But even if there were a yoke incompatibility, it would have no bearing on a crt replacement, for one could always replace only the crt, leaving each yoke with its original mac. When...

See http://68kmla.org/files/classicmac2.pdf for basic troubleshooting hints. Pay particular attention to the sections on the yoke connector, C1, and voltage adjustments. The fact that you hear a bong is highly encouraging.

Your technician is deeply confused -- so much so that it brings into question his abilities. It's obvious that he does not have the slightest understanding of how a crt is driven. There is no "voltage rating" for a crt, so I have no idea what the numbers 30 and 400 are supposed to mean. He is...

Since it's going through its usual boot process correctly, a great deal is working. Since the hard drive needs both +5 and +12, all the supplies are basically ok. In the absence of other data, loss of raster subsequent to loss of vertical deflection still screams "connector trouble" to me. Yes...

When you turn it on, does it seem to come to life (makes the bong sound, disk activity happens, etc.)? If not, you have bigger problems than a (possibly) bad vertical drive chip. Check supply voltages (if you haven't already done so). Check the CRT connector to make sure it hasn't worked loose...

From the sequence of symptoms, I doubt that the vert IC has died. It is much more probable that the yoke connector (P1) simply needs resoldering (use fresh solder; do not simply reheat what's there). Before spending the money on ordering a replacement IC, try the easy thing first. Be sure also...

Yes -- thanks, Mac128, for correctly interpreting what I wrote, despite my unintended efforts at obfuscation. :) Those drives were certainly odd-looking, as were the floppies they used. I had a chance to buy a box of broken Twiggy drives back in the late 1980s. In a rare moment of...