Mac 512ke no sound

[jgstratton]

I have my original Mac 512ke I've had since I was a kid in the 90s. I'm trying to show it some love after all these years (and a career in computers that started with this little mac) and get it more than fully working.

While the machine appears to work after some tweaking, audio doesn't. I've tried the normal stuff from the Dead Mac Scroll. I also have access to a mac plus (not mine), and tested that motherboard in this machine (and its audio works!). So I am fairly sure its something on the motherboard. Plugging headphones in produces no audio. I did look at the audio port a little closer, and it seems clean. Testing the pins on the audio jack; it seems like its properly detecting when something is plugged in versus unplugged, which to me additionally shows this isn't a stuck switch in the audio port.

This is usually the point where I would "when in doubt, recap". But I've heard somewhere that this is a three layer board(?), and have had bad experiences with mucking with board with more than two layers. Also, I really REALLY dont want to mess up this computer, so I would like to have some level of confidence before replacing those two caps.

I apologize for the flood of messages today; I'm trying to catch up on my vintage computer fixing backlog.

 

[Phipli]

This is usually the point where I would "when in doubt, recap". But I've heard somewhere that this is a three layer board(?), and have had bad experiences with mucking with board with more than two layers. Also, I really REALLY dont want to mess up this computer, so I would like to have some level of confidence before replacing those two caps.

Probably doesn't need a recap.

Can you take a photo of the Sony branded chip on the logic board as well as the surrounding few inches of board and chips? Nice high resolution, well lit (natural light in a window if possible) photo where details like traces and part numbers can be seen clearly.

Edit - here is where I show my ignorance of the very early macs - can't see a Sony chip in a photo.

 

[Phipli]

Perhaps these sort of areas?

 

[unity]

Did you reflow the critical solder joints on this machine? There are several on the analog board but people often overlook the logic. It needs a reflow too at the connector. There is a chance that you have a cold joint causing the audio issue. So I would reflow the connector just to rule it out.

 

[jgstratton]

Unity,
I did test continuity with the cable, but to be sure I just re flowed the cable connector a couple minutes ago. Unfortunately, it didn't change the sound issue.

Phipli,
I'm starting to realize why people care about cameras on their phones; these images below are probably not useful (Pinephone strikes again!). Hopefully I can add some color, however, to maybe make up a little for my phones camera:

The two small chaps closest to the keyboard connector are marked:
74LS161A PC
F
8635 KOREA

The larger chip in that area is labeled:
639 V D394S
VL6522-02PC
MEXICO R

And the one near the serial port is:
34002B
TL082AC
K8630

The traces appear to be fine to me, but Ill test continuity right after posting this. Ill respond to this post if anything crazy pops up.