LC No Longer Chimes

[AwkwardPotato]

I recently picked up a Macintosh LC with 12" monitor, and when I plugged it in, I got nothing. I then replaced the power supply with one I had recapped earlier, and the fan spun up, and it chimed. However, there was no video output, and when I looked inside to pull out the Maxell battery, I noticed that the area around some of the capacitors was covered in electrolyte. Upon pulling out the board, I noticed that a liquid had been spilled on the board at some point, as there was a brown goop around the back edge near the ports and on a few chips near the audio circuitry. The entire bottom of the board was also coated in a different type of residue. After cleaning the board with 91% IPA, it no longer chimes.

What should I do to get the board working again?

 

[Unknown_K]

Recap the motherboard if there is no damage to traces or chips(if there is it is toast).

 

[AwkwardPotato]

There's only minimal damage to a few traces, at least minimal enough to be bridged and repaired, so I'll go ahead and order new caps. Not only will it not chime, but it no longer attempts to read from the disk drive.

By the way, in order to test the monitor, will it display an image if connected to a PowerMac 6100? I've connected it via the HDI-to-DA15 adapter, and it won't display anything. When it's turned on, I can hear a faint buzzing noise.

 

[AlpineRaven]

caps.. caps... thats the problem! I have one that is completely silent and another one that makes crackling sounds
Cheers

AP

 

[Unknown_K]

One of my first freeycle finds were two LC IIIs over a decade ago (ex school machines). One worked fine and the other whistled when I fired it up and never booted again (until I recapped it). So bad capacitors have been a problem for a while now.

 

[AwkwardPotato]

I just recapped the motherboard, in addition to patching about half a dozen bad traces, and the machine still does not boot. I've also washed the motherboard and let it sit to dry for over 48 hours. When the computer is started, the fan starts, the speaker clicks, and the flatscreen VGA monitor I have connected detects a signal (goes from the "No Signal" screen to a solid black one, but the power LED is green), just there is no image on the screen. I have the ROMs in the correct order (I think), I've installed a stick of VRAM, the power supply voltages are all correct, and the machine has a fresh PRAM battery installed.

 

[Unknown_K]

Recheck the RAM you used, and the VRAM. Which monitor did you connect it to?

https://68kmla.org/forums/uploads/gallery/album_184/gallery_6211_184_2351181.jpgshows the motherboard and ROM locations (and orientation which is important)(not my picture).

 

[AwkwardPotato]

It exhibits the same behavior whether I put in SIMMs or not, even known working SIMMs. Bad motherboard?

It's connected to a Dell LCD through a DA-15 to DE-15 adapter, set to VGA (640x480 @ 60Hz).

 

[aplmak]

If also check and recap the power supply.. Those go bad too!

 

[AwkwardPotato]

I don't know why or how, but after doing nothing to it for a few weeks, it now chimes!

Rarely, it will play the normal startup chime, and even eject disks that you put into it.

Less rarely, it will play the normal startup chime, and then play the death chime a few seconds later.

Even less rarely, it plays only the death chime.

Most of the time, it does nothing.

Even after using the double-tap method and putting in a fresh PRAM battery, it never displays a picture on either the 12" RGB or VGA LCD.

 

[AwkwardPotato]

The exact symptoms, after reset from keyboard, seem to change depending on which combination of SIMMs are installed:

With 0 SIMMs of any type: Almost always does nothing, if it does anything, its a full Chime of Death

With just the VRAM SIMM: Almost always plays the normal startup chime, but then plays about half of the Chime of Death, then the audio cuts out

With the VRAM SIMM and one RAM SIMM: Maybe 2/3 of the time, it plays a normal startup chime and then plays a full Chime of Death

With the VRAM SIMM and both RAM SIMMs: Seems completely random as to whether or not it does anything

 

[AwkwardPotato]

I should also mention that it almost never does anything, no matter what is installed, unless you reset it from the keyboard first (Ctrl+Cmd+Reset).

 

[Scott Baret]

This sounds like a case of a damaged logic board from none other than capacitor goop.

Sometimes, cap goop can get on other things and cause problems. Before my main LC was recapped, it had a video issue where it would start displaying gibberish on any mode other than Thousands of Colors. A recap fixed the problem, and apparently it needed a lot of cleaning.