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Additionally, we can juuuust see C2 is X2-rated. That 250V rating is cutting it too close for comfort on an UK line voltage.
Care to get us a pic of the underside of the board? That should allow for deducing how C1 is wired.
Presumably 220nF and 470nF (a.k.a. 0.22uF and 0.47uF), X or Y rated, depending on how they're wired (Y if line to earth, X if line to line), rated at higher than line voltage (typically 270V if memory serves?). That's the general ballpark formula for line filter caps.
There is a rubber roller what grows beyond the original diameter and stops holding to the metal shaft that is driven by the eject mechanism. You can try disassembling it and gluing the roller to the shaft. Or just not bother with reinstalling the drive, usually they're dead anyway. Some respond...
I got a 6360 in a trade, and the guy took 2y to send it out. In these 2y, the battery grenaded and ate half the board. There was corrosion *inside* the CPU, once I delidded that for funsies.
If it has the sliding clip, it's Ethernet. That's not Mac video, nor will it ever be. Next thing someone will tell me is that's a PC joystick port because it's a DA15, too.
+1.
What @zigzagjoe said. If you trace the harness between analog and logic board, you'll see that two of the monitor ID pins on the CC board go nowhere, and one beeps to the main ASIC.
Unfortunately boardviews really are a modern mac thing only. There's 9600 schematics attached earlier in this thread and that would be of some use, but it'd still be a lot of wandering around in the dark to use that to fix corrosion damage on an 8500.
No. You're looking in the wrong spot. The RTC is driven by Y4, and you might have issues with corrosion there, or with the RTC itself. Remember to also check the bottom of the board. Crystals/oscillators seldom fail on their own.
Maybe yours just isn't a fishy mess yet. Who knows how long both of mine spent on a charger before they got whacked onto ebay as "for parts".
I'd eventually like to own a good one, still.
I don't have a 2300c so no data there. The same thing probably applies to 210-270 but in less stern fashion (DC-DC design is similar but not the same). I just know it is absolutely critical on 280s and running them for 30s with a bad cap there can be a death sentence. In my case, a recapped 280c...
Can't point ya to any guides, but there's a half dozen under the upper frame, next to the power connector, and the one you should be most concerned about is immediately visible once you lift the keyboard, next to the 2nd transformer you see.
I like Würth's solid polymer caps as replacements...
At least it's not hung, then. Given your lack of chime, and the corrosion it had, I think it's plausible you have trace/via damage, at minimum next to the audio circuit, possibly elsewhere too, which can also be cause for these odd "almost boots but not really" symptoms.
Visually inspecting the...
It slowly eats away, but the real danger is in plugging it in - you happened to be lucky to not have the power adaptor.
It really is a matter of replacing, not just inspecting - every 280 out there is bad by now.
Has it been recapped? Duo 280s WILL DIE if C72 has leaked/degraded. U2 (I think) shorts out and the 5V rail is shunted to the 24V of the DC input, killing everything inside.
Mouse pointer = machine has already chimed (or thinks it did)
Does the pointer move at all, or does the machine appear to hang? Where did you check for the missing -12V? (if floppy port: SE/30s aren't meant to have -12 there).
Put down the parts cannon - understand the failure first.
It could be faulty/dirty RAM. It could be the overclock. It could be a genuine hardware failure.
Knock the machine down to 400MHz and see what happens. Run it on a single RAM stick, if you have more than one. If still troublesome, see, if possible, if it works off the onboard ATA controller.
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