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You're completely right. Looks like I was incorrectly filtering for MOSFETs with < 100mOhm on resistance, when I meant to be looking for < 1 ohm. For example, the Infineon IPP80R280P7 has better specs than the IRF740 in essentially every way: voltage rating, on resistance, gate charge. I...

Yes I'm sure it must be because using a MOSFET saves the cost and complexity of the base drive circuit. Even the early Classic analog board uses a MOSFET for the HOT (IRF640 in that case), while the earlier compacts use a BJT (BU406) with a transformer. Since the Classic was designed for low...

After a long hiatus, I'm going back to this resolution-changing project armed with a new approach. I've established (as techknight and others have found) that the flyback transformer on most of the compact Macs can't be run at VGA or higher resolutions -- no matter what external capacitor is...

Using a larger capacitance in this situation should be completely fine, as long as the voltage rating is sufficient (which it is).

I used to use hot tweezers but I'm a convert to the twist method. It's hard to say for sure but I suspect there is actually less risk to the pads this way. The pad is more likely to delaminate when hot, and it can take quite some time to get that ancient solder to flow again. The pads are also...

It appears I spoke too soon about the flybacks being the same. Having desoldered the flyback from the VGA monitor and tested the various winding resistances, there's no question that it is pinned out differently than the one on the Classic. A bit more digging reveals that the marking "E58491"...

Yep. Though caps may not be the only problem: I have a couple of these CD drives (Quadra 650 caddy loaders), both partly malfunctioning with leaky caps. Replacing the caps, surprisingly, didn't make much difference (see this thread). There may be optical issues on these drives as well.

Wire wrap wire (usually 30AWG) works well for repairing bad traces.

If you haven't already done it, start by reflowing the connectors on the analog board to the PSU and the CRT neck board, even if they look okay. Better yet, remove the old solder and add some new solder in its place. If you have another SE, you could swap power supplies to see if it changes...

C12 is a power supply bypass, according to the schematic. It's probably not directly the source of the problem. But indirectly, by leaking goo everywhere it may be your culprit! The recap has to be the first step, otherwise you'll be chasing after new and weirder problems as time goes on. If...

Recapped? If not, that's step 1. Step 2 is to check around UK4 (the RTC chip) and Y1 (the 32kHz crystal that runs it), looking for bad traces. There are four signals from UK4 to UK12 (VIA1). Any of them goes bad from cap goo and the clock probably wouldn't run.

Whatever it is, I'm interested to find out because it's very similar to the lines I ended up with when I did some resolution changing experiments on the SE/30. When I drove the flyback at one frequency (22kHz) and the yoke at another (31kHz), I got horizontal lines like this, though more...

Yeah, it appears the switch was sometime in 1991. There's a thread about it here somewhere. All the Classic IIs have the newer flyback (which also has a totally different analog board circuit), and some of the later Classics do. The older ones have essentially the same horizontal circuit as the...

Just made a useful discovery! Here are some photos of one of those 9" (S)VGA monitors that I bought off eBay a while back: https://68kmla.org/forums/index.php?/topic/26313-compact-mac-retina-display/page-2&do=findComment&comment=279984 Notice the marking on the flyback in that monitor...

Interesting timing. I did some experiments on SE/30 screen resolution a year or so back, but I'm just about to revisit the topic: https://68kmla.org/forums/index.php?/topic/26313-compact-mac-retina-display/ The limiting factor is the horizontal scan rate, which is 22kHz on all the compacts and...

I can try that. The main question is how to get the thing apart! The diode is inside a big black case with the lens on a spring-loaded mounting near the front. I presume it's a little voice coil motor in there to micro-align the lens to the track. I was hesitant to start pulling the thing apart...

I don't think there's a physical eject switch on these drives. I suppose it could have something to do with the caddy not going in far enough. At first, it would never go in far enough for the "caddy loaded" flap to come down. Now that flap comes down all on its own (?). I haven't yet figured...

It looks like a vertical sweep problem, and if whacking it temporarily cures it then it's very likely mechanical, probably a bad solder joint. Check and resolder the components in the main signal path of the vertical yoke: especially C9 and R13, and height potentiometer R4. Secondarily check U2...

Resurrecting this thread to ask about a closely related set of symptoms: I have two Quadra 650's that each came with an internal CD drive (Sony CDU561-25), each of which has different problems. Drive #1: about 80% of the time, it ejects the caddy immediately after putting it in. If it does keep...

Can you post a photo of the effect?