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Probably related to U7 or U8. Hard to tell from the photos but the trace connecting pin 2 on the egret (that runs under C6) looks broken. Maybe just a shadow or some toasted flux? Sometimes there can be a solder bridge hidden underneath the chip too.
Y1 does not typically go bad, but essential...
I believe egret failures typically result in no boot or display action whatsoever. That said, be sure to check continuity between Y1 and C56 on the underside of the board.
Have you recapped the analog board? Good voltages?
Sounds basic, but check the edge connector is clean (socket side too)...
Dang. Shame it’s not just a bad trace.
Board is very similar to an LC II, which has a 341S0847, but I’ve not heard of a successful transplant, not that it can’t work, just no successful attempts.
Apparently the LC 550 used either the ‘0417 or the ‘0788, so the latter might work.
You can...
As I mentioned in your Trading Post post, worth checking the crystal. If the connection rots out between Y1 and the CUDA, you'd get no response from soft power. A trace runs from Y1 to a via, then to a ceramic load cap on the backside of the board. C6 very often rots out that trace or via...
Nice surgery doc.
I’ve seen this done a few times on that exact chip, common corrosion spot I guess, nice it can be resuscitated.
I’d put a bit of clear enamel or conformal coating on there if you haven’t already.
Yep, cap leakage, definitely. Coming through from the cap cluster on the opposite side. Actually not bad compared to many Classic ABs I see nowadays. Often that whole section is rotted…
Nice job!
They do respond best with low ESR caps, though it still should’ve still operated for a while. Maybe one of the first round of new caps was a dud, or the flaws in the circuit (which you’ve now addressed) burned one out.
Yeah probably two separate issues.
So these aren’t recent pictures, then? I do see a lot of evident corrosion right in the midst of that sound circuitry. Not seeing anything obvious near the SWIM and SCSI chips, but quite plausible there’s a bad trace or resistive via hiding in that cluster. (I...
So you recapped both the analog board and logic board, then? Hmm.
How are your voltages looking? Did you touch up the solder on the back side of the AB particularly at plug and wire connectors? Solder joints are often cracked in those areas.
Yup, this. I've had a couple CCs with darker spots like that, they cleared up when I let the degaussing coil do its thing.
You will hear a very slight "chirp" when you first hit the power switch, if you don't hear anything the coil might not be connected. Don't boot it up, just leave it like...
Yeah I wouldn’t trust a diode reading in circuit, probably OK if you just replaced it.
I’ve occasionally had problems with PP1, it’s close enough to the big cap cluster so seems to take a hit.
Check the backside of the analog board for cracked solder joints, particularly at plug connectors / wires and the transformers. Not as common as on SEs and Pluses, where it happens almost 100% of the time, but still find it shows up often enough on Classics.
We’re certain the LB is good?
@zigzagjoe is giving good advice here. I have a few comments I'll try to add tomorrow. Just wanted to drop in with a quick: wow! You've done a lot of work to restore this board, I'm impressed. Would love to see pics of the analog board, but yeah proceed as though a recap is a necessity, because...
They do this when you pay for extra protection, Im assuming? I’ve often hesitated to pick up Color Classics and whatnot because I assumed they wouldn’t arrive intact, but molded foam would be worth the extra expense.
It should boot without a VRAM SIMM, yes.
Places to start, I’d look for corrosion on or near the soldered memory chips. Very common cause of death chime. Another problem area could be U7 and the oscillator beside it. And I’ve had dead video as a result of bad ROMs, worth reseating or swapping...
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