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Backlit Portable - No sound from speaker, jack works


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I've completed the recap of my new-to-me backlit Portable.

 

Good news is the machine is booting and running very stable, even on the original Conner drive.

 

What I've found, though, is that I'm not getting sound through the internal speaker. When I plug in headphones, I get sound, but it has electrical interference like a hum/static, which can vary when the screen updates etc.

 

I plan to go back in and check my work, but thought I'd throw this out there in case the collective has any ideas or previous experience on where specifically to check.

 

Thanks!

 

PS - yes, the speaker is plugged in :-)

 

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there is a via that runs right around where those 3 caps sit above the video chip, that passes the current through to the speaker. it opens. 

 

the noise/static is also caused by electrolyte still stuck in that same area, or bad traces to decoupling capacitors. 

Edited by techknight
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3 hours ago, techknight said:

there is a via that runs right around where those 3 caps sit above the video chip, that passes the current through to the speaker. it opens. 

 

the noise/static is also caused by electrolyte still stuck in that same area, or bad traces to decoupling capacitors. 

Hmm - didn't see anything obvious with a quick visual inspection. Will have to wait until Monday or Tuesday night when I can get it under the magnifier.

Edited by ScutBoy
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Oh - I believe you!

 

This is the reference I found for the backlit board:

 

https://recapamac.com.au/macintosh-portable-backlight/

 

I assume you mean the three caps in the upper right of this picture.

 

I'm also going to carefully re-check the three in the lower left. It was tight to get those three down next to the keyboard connector, but not sure if they would be involved in this issue or not.

 

Are you aware of schematics for this board floating around anywhere?

portable_backlight_recap.pdf

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yes, the 3 caps in the upper right there. 

 

I also believe there was a 22 ohm resistor that is in between the circuit too. so basically the Audio jack runs over to that section, passes through a 22 ohm resistor, and then to the speaker connector. 

 

And no, the M5126 schematics are not available as far as I am aware. Only the M5120. 

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  • 2 weeks later...

Thanks Techknight, my "new to me" non-backlit portable was doing the same thing.  Using your instructions and the clarifications from ScutBoy, I was able to locate the problem on my board and repair it.   Mine was open between the positive side of C9 and the Sound Output from U15B (Sound Left, Pin 11).

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  • 2 weeks later...
On 11/5/2020 at 8:38 AM, SteveHere said:

Thanks Techknight, my "new to me" non-backlit portable was doing the same thing.  Using your instructions and the clarifications from ScutBoy, I was able to locate the problem on my board and repair it.   Mine was open between the positive side of C9 and the Sound Output from U15B (Sound Left, Pin 11).


hi is that the Pin 11? Mine is open too.

 

 

E64928C2-1EED-4BCF-AF82-2A64449E3BA3.jpeg

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On 11/5/2020 at 8:38 AM, SteveHere said:

Thanks Techknight, my "new to me" non-backlit portable was doing the same thing.  Using your instructions and the clarifications from ScutBoy, I was able to locate the problem on my board and repair it.   Mine was open between the positive side of C9 and the Sound Output from U15B (Sound Left, Pin 11).


thanks! I managed to get my sound working!!! Same problem as yours. 
 

@techknight thank you too. 
 

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On 11/4/2020 at 11:42 PM, 360alaska said:

I found a bad speaker once. To anyone reading this in the future, I'd suggest ohming out the speaker before proceeding further.

 

I think 360alaska wins here - I pulled my Portable open again, and C9->U15B toned out OK. For what its worth, C10 and pin 11 on the corresponding Sound Right chip toned out OK as well.

 

Testing the speaker with a multimeter I got no resistance across the speaker terminals, and trying to jump the terminals with a battery I got no pop nor movement of the voice coil.

 

I guess I can put the speaker out of my non-backlit portable to test. Anybody have an organ donor out there?

 

Using headphones, there's still background static-y noises that change in intensity and pitch as things on the screen change, so I guess there might also be some further diagnosis or board cleanup to do. With the speaker out, you can't hear any of it, so maybe I'm better off leaving things alone! :-) Everything looks clean and clear as best as I can tell in that part of the board, so I should probably start looking further out around the other areas where caps were replaced...

 

 

 

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  • 4 weeks later...

Just to close the loop here for future searchers...

 

I got a replacement speaker from 360alaska, and now sound from the speaker works as expected!

 

There's no static-y noises out of the speaker, but they are still there when I plug headphones into the rear jack. I guess that means that there's still some tracing to do on the sound-out circuit(s) for the jack, but since the speaker works and sounds great, that's pretty low priority for me.

 

Thanks again to 360alaska for the diagnosis tip and the nifty replacement speaker!

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On 11/18/2020 at 4:08 AM, glay78 said:


hi is that the Pin 11? Mine is open too.

 

 

Sorry for the late reply here, I haven't checked in on this thread in too long.  Yes, your image shows exactly where mine was open. 

 

Looks like we have two different issues going in this thread, with Alaska360 and ScutBoy having a bad speaker, and glay78 and I with that open trace.

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