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Replaced with a working 74F240 to no avail; back to the drawing board.

Too late to edit, but, after flipping through the Dead Mac Scrolls, I came across this:  "On startup, you get the normal startup chime, then you get a high note, followed by an even higher note, followed by a do-do-da-da sound. Then the raster blacks out." My raster doesn't black out, but, that...

Howdy everyone! I'm looking at a Mac IIx that I've cleaned, recapped, and replaced the batteries on; there appeared to be damage to one trace between a couple of pins on UB2 that I bodged, and that looks like all the visible problems I could find. When powered on, the screen comes up white...

Hahahaha! Oh physics, you troll. That's what had me so stumped, too! I figured I was just interpreting things incorrectly due to the fact that, on pretty much every standard res monitor used in an arcade cabinet from the same era, the resistors that B+ ultimately traverses are all gigantic...

So, a nearby friend mentioned he had a working monitor and offered his for reference; I'm a bit stumped - it looks like it is .82 Ohms, but that seems so dang tiny an amount of resistance. I don't think the multimeter could measure low enough (I'm assuming the 2 Ohm reading is an error), but...

Doesn't look like I can edit my previous post, but, that may be either grey or violet for the first band; after looking at mine again under very bright white light, it is difficult to tell if it is either grey or violet. Would there be that big a difference between .72 Ohms and .82 Ohms? I know...

Okay, after some more googling, these look like 820 mOhm 5% 2W resistors - Grey | Red | Silver | Gold. I'm basing this off of my photos, the recent one above, and (amazingly) an M1296 diagnostic video that I was surprised to find was made by you (screenshot below)! :)  I'm guessing the color...

Hehe, sorry to jump the gun on you, there. :)  Both resistors appear to be toast, unfortunately, as a multimeter reading fails on both. I've been searching for photos of the chassis to no avail as well, sadly. Any help is tremendously appreciated, and thank you again for your assistance! Edit...

Sweet deal! So those are 5.5K ohm resistors, then?

So I pulled the chassis and, as suspected, the area under C418 is pretty rough. The good news is that everything except for one trace (between the two resistors next to C418) tests okay; some of them are pretty roughshod, though, so I'm going to jumper anything that looks eaten just to be safe...

I was hoping that wouldn't be the scenario, lol. Thank you so very much for pointing me toward that; I'm going to start looking for damage. I'm assuming the horizontal transistor will need a replacement as well?

So I got my hands on a 12" RGB monitor, but it does not appear to have much life to it. The font LED comes on, but there seem to be no other signs of life: no degausser hum (though that can vary from monitor to monitor) and no neck glow. C418 looks like it's leaked some fluid but, from what I've...

Okay, so after some additional examination it is safe to say that the +5v rail is, indeed, shorted to ground somewhere. I got suspicious after testing for bad caps and, sure enough, the +5v pins on the logic board's PSU connector all show continuity with the GND pins. I've removed (and...

Hey! We're back to square one, but at least it isn't as dead as I had assumed. Voltages look fine so far all over the place, but I'm still testing. This thing doesn't need drives hooked up to boot to the [?] screen, does it? I know that's probably a dumb question, but this is an enormous...

Well, went and checked - C155 is shorted, along with just about every other capacitor. The +5v rail is shorted to ground somewhere; I'm guessing that probably fried a few things. Oh well, it will make a nice shelf piece.

Plastic, which is what made the smoke/burning smell; there wasn't any visible metal anywhere nearby, which is what threw me for a loop. I just got back from running errands, so I'm going to eat dinner and have another look in a few.

Same result, unfortunately; not sure why I had it disconnected in this image. However, I fear it may be dead dead now. I powered it up, noticed a burning smell, and then the PSU cut off a moment later. I looked under the board and noticed a couple of burnt pins on the bottom first socket for...

Regarding the VRAM/ROMS: good to know - thanks! :) I've tried four sticks of matching RAM in every bank to no avail; I have a green light on the logic board, but still no chime or video. :(  The PRAM battery is new - pulled from a working machine, so I know it's a good one - but it's also...

Howdy, everyone! I just got ahold of a Q950 with a dusty, but other wise good looking, logic board that will not boot. The PSU appears to be putting out the correct voltages when powered on, so I think I can rule that out. Any display I hook up to it registers that a signal is being sent, but...

Got the DFAC replaced with one from a very much dead Classic II (RIP, old friend) and audio is back! The LC lives again.