The LC III that chimes death with no video.

[Big Ben]

Hi and happy new year /o/

So I had this LC III motherboard sitting alone for a while, death chime, original caps. But beside that seems in great condition.

I did a recap and indeed after cleaning, the motherboard looks fine, almost like new.

Great! Recapping done nicely, no surprises, except... it's still doing the death chime. Ugh. And I can't get any video, so no error code to read, I've litteraly no idea what's going on here.

Here is few things I should check though:

1. This reversed capacitor thing on the LCIII:
   
2. Check rails voltage
   
3. Video circuit maybe damaged, must check if there is some signals down here
   
4. Death chime happens just after boot chime, so must fail on an early check
   
5. ROM: checked and ok. Swapped with known-good ones, same result.
   

Yet another interesting case to solve :scrambled:

 

[djhaloeight]

My LCIII+ is having this same problem. My 12” LC monitor also died at the same time. Thinking I had a brownout or something. I had forgotten to unplug them after I used it last. The motherboard on mine is all recapped, had been working fine. I get a normal startup chime then the chimes of death. I need to get another monitor to see if I’m outputting video and see if there’s a fault code shown.

Have you tried reseating RAM and VRAM? Mine doesn’t do the death chimes if the VRAM is pulled but it also doesn’t boot up.

 

[slipperygrey]

I have an LC III with the exact same symptoms. Did you get any closer to figuring out how to fix yours?

Mine had practically no cap leakage and no signs of corrosion on traces or legs, but I guess there's still the chance that there is some hidden damage somewhere...

And yes, all caps have been replaced.

BTW, as per LowEndMac the LC III/+ has 512kb VRAM on-board so I think it should run without a VRAM SIMM installed.

 

[chiptripper]

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 with known good ROMs if that’s a possibility.

 

[djhaloeight]

Mine turned out to three corroded open traces on the RAM address bus. Probably from the original caps that leaked before I had them replaced. I ended up having max1zzz swap my chips and components over to one of his new reverse engineered purple motherboards. It’s been fine since

 

[slipperygrey]

I'm embarrassed to say that removing the caps again, cleaning the pads, and then resoldering the caps got my LC III up and running. I must have had a cold joint or two there. Lesson learned that even when the cap leakage is minimal, getting good joints on those pads can be challenging.

 

[djhaloeight]

I'm embarrassed to say that removing the caps again, cleaning the pads, and then resoldering the caps got my LC III up and running. I must have had a cold joint or two there. Lesson learned that even when the cap leakage is minimal, getting good joints on those pads can be challenging.

Any easy fix is a good thing!