Mac Plus speaker not working

[Ken Newman]

I have a few Mac Plus computers that I'm getting ready to sell. One of them doesn't make any sounds out of the speaker, but sound does come out of the headphone/external speaker connector.

Just wondering if anyone knows the usual reason for this failure? 

I've tested the speaker with an ohmmeter and it checks out okay, so I'm figuring that it's NOT a case of a bad speaker. And as I said above, sound DOES come out of the headphone connector, just not out of the speaker. 

Volume level in the control panel is indeed turned up to 3 or 4.

Thanks!

Ken Newman

(I do live sound for a living, so wouldn't it figure that I'd have some sort of sound issue! )

 

[cheesestraws]

My first port of call personally would be to check pin 4 of J4 on the analogue board.  That is the pin that carries sound from the logic board to the analogue board, and that connector in general is a bit notorious for developing dodgy solder joints.  Usually it's pin 1 / video that goes, but I know a number of people just routinely reflow the whole thing pre-emptively whenever they get a Plus...

 

[Ken Newman]

Thanks!

I’ll definitely check that out! I think I already re-flowed all the joints of that connector, but I’ll double-check!

 

[cheesestraws]

I think I already re-flowed all the joints of that connector, but I’ll double-check!

Having thought about this some more today...

Looking at the back of the board, it looks a lot like the speaker is just between Sound and ground on that connector, I can't see any actual audio amplification happening on the analogue board.  I may be wrong, but if that's the case then ... there's really not much to go wrong there.

Looking at the logic board schematic (here), there's only a resistor between the headphone jack and the speaker.



But I reckon it's a jack with a switch in it, because that would make sense to have inline to switch off the internal speaker when the headphones are plugged in.  So having actually thought about it a bit more, my current bet is that something has physically damaged the switch in the jack connector.  It's possible that the resistor has gone bang, I suppose, but there's a lot more to go wrong with a switch so that is probably where I'd look, probably just with a continuity meter to start with...

 

[Ken Newman]

Ahhhhhh! Thanks ever so much for taking the time and thinking about it more!

I'm sorry, I should’ve mentioned that the issue exists no matter which logic board I put in the computer...so I think it’s safe to say that it’s not related to the logic board. Also, fwiw, I traded out the analog to logic board wiring harness, and the issue persists. I think your first suggestion of checking all joints on the analog board is where I’m headed, at least to start, anyway.

 

[cheesestraws]

Ahhhh.  Well, bang goes that theory then :-D .

On the analogue board, the speaker literally seems to be tacked across from Snd to Ground, so you haven't got many points you need to do troubleshooting and the problem ought to be simple (hah.)

 

[Ken Newman]

Well despite the fact that I tested the speaker using an ohmmeter (tapping the test leads on the speaker terminals produced crackling from the speaker and by that method it tested "good"), the culprit turned out to be the speaker itself. Swapped it out with one from another analog board, and now it's good to go!! Crazy!
Now if I could just get all my 800k floppy drives to work, that would be amazing!!

 

[glay78]

Well despite the fact that I tested the speaker using an ohmmeter (tapping the test leads on the speaker terminals produced crackling from the speaker and by that method it tested "good"), the culprit turned out to be the speaker itself. Swapped it out with one from another analog board, and now it's good to go!! Crazy!
Now if I could just get all my 800k floppy drives to work, that would be amazing!!

Would you be selling the analog which the sound doesn’t work?

 

[Ken Newman]

Would you be selling the analog which the sound doesn’t work?

I'm sorry but I do not think I will be selling the analog board on which the sound doesn't work, because believe it or not, once I moved the speaker to the other analog board, it now appears to work just fine.

Also, I'm thinking about re-capping the analog board so that when I sell it, hopefully I can sell it for more than if I do not re-cap it.

Thanks!

 

[glay78]

I'm sorry but I do not think I will be selling the analog board on which the sound doesn't work, because believe it or not, once I moved the speaker to the other analog board, it now appears to work just fine.

Also, I'm thinking about re-capping the analog board so that when I sell it, hopefully I can sell it for more than if I do not re-cap it.

Thanks!

Ok thank you