M5126 Portable with sound problem

[and.short]

Hello all,

I would really appreciate your assistance in my quest to restore a mac portable (blacklit version). The computer was purchased from ebay as faulty.
I restored the main battery and washed the motherboard in the dishwasher and was able to boot it many times with everything working except audio.

I then performed a full recap myself with quality tantalum capacitors from mouser.
The computer now tries to chime (makes some distorted sound), but at that point freezes, shows garbage on screen, and then throughs a sad mac with random numbers (different each time).
Sometimes it might boot successfully, works fine but when I try to play audio (from the control panel) the system 7.1 will freeze although mouse will continue to move.

Does anyone have similar experience? I have multimeter and scope meter, but no schematics. I followed the line from the speaker, goes to C9-, and C9+ goes to SOUND LEFT chip.

Observations
a) I have the same symptoms with speaker connected/disconnected
b) Same crackled sound from headphones
c) It seems that when audio is played, it shorts something out.

I appreciate your input, or at least some kind of schematic to follow traces/make measurements. I don't even know the pinouts on the sound chips. I cannot make out any of the writing on the sound chips either.

 

[SteveHere]

Hi and.short, Although I have worked on a couple of Mac Portables I have not seen that exact issue before. I'm afraid there is not a schematic on the Internet for the backlight version of the Portable, at least not that I'm aware of. There are alot of folks on the forum here with more experience with these machine than I have, but I'd suggest the usual things, carefully clean up all the flux residue, double check your solder joints and make sure you haven't created accidental shorts w/ the traces near the capacitor pads, etc.

It may be valuable for you to read articles about similar issues, there's some really good stuff in this section of TinkerDifferent, and there's some great Portable content over on this forum, too...

68k PowerBook

From the Portable to the 190cs.

68kmla.org

 

[Androda]

Could you post the sad mac code numbers? I know you mentioned they're different most of the time, but those sad mac codes hold valuable information on why the system doesn't always boot.

It sounds like there are damaged traces around the board, or a chip that's unhappy, or something's up with the recapping work. Having run it through the dishwasher it might be more difficult to find signs of corrosion, but overall the board needs a really good eyeball to see if traces are broken or component legs are corroded.

 

[and.short]

Hi thanks for your replies. Here is a short video showing the issue, along with the sad mac codes. Hopefully you can also hear the speaker noise.

 

[Androda]

These are all the codes I saw in the video, just to get them down in text:

0000 0001 | 0000 FFFF
0103 097C | 0E7C 24DC
0300 1583 | 0000 1FFA

As per the Sad Mac Reference (under the Macintosh Portable section):

The first code 1 / FFFF means the ROM test failed. This is some sort of ROM checksum I believe.

The second code 0103 097C / 0E7C 24DC is rather complex.
097C means there was a 68000 "Line A" exception (based on 0900). The C in 097C might mean it can't access the SWIM. It might also mean major error 8 OR-ed with major error 4 (though there is no major error 4 listed on that page). Error 8 means there's a data bus failure on the data line bits indicated by the minor error.

The third code is similarly messy.
1583 means "Interrupt Level 6" exception (based on 1500). The 00001FFA error has appeared in many posts, but this one suggests it's an issue with the CPU NMI (interrupt) lines.

Overall it appears to me that this system has random corrosion and connectivity issues. Do you have close-up pictures of the RAM, CPU area, and the corner by the reset/interrupt buttons?

 

[and.short]

These are all the codes I saw in the video, just to get them down in text:

0000 0001 | 0000 FFFF
0103 097C | 0E7C 24DC
0300 1583 | 0000 1FFA

As per the Sad Mac Reference (under the Macintosh Portable section):

The first code 1 / FFFF means the ROM test failed. This is some sort of ROM checksum I believe.

The second code 0103 097C / 0E7C 24DC is rather complex.
097C means there was a 68000 "Line A" exception (based on 0900). The C in 097C might mean it can't access the SWIM. It might also mean major error 8 OR-ed with major error 4 (though there is no major error 4 listed on that page). Error 8 means there's a data bus failure on the data line bits indicated by the minor error.

The third code is similarly messy.
1583 means "Interrupt Level 6" exception (based on 1500). The 00001FFA error has appeared in many posts, but this one suggests it's an issue with the CPU NMI (interrupt) lines.

Overall it appears to me that this system has random corrosion and connectivity issues. Do you have close-up pictures of the RAM, CPU area, and the corner by the reset/interrupt buttons?

Thanks so much for looking into my issue. I still believe that the problem is audio related. During the startup chime, it causes something to fail. Sometimes it fails during rom checksum check, sometimes a bit later, sometimes it will happily boot and work fine until I play audio again.
I will upload high-res photos in the upcoming days. Although the board is in excellent condition even before I cleaned it twice in the dishwasher and scrubbed it with toothbrushes etc. I am more suspicious of something shorting out rather that cut traces.

 

[3lectr1c]

Dishwasher method of cleaning can be harmful to the board. I wouldn't use it again if I were you because it can cause already weak connections to become broken, and the fact that it cleans the board hides any previous or new damage really well, which might explain why you're having a hard time finding anything.