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Macintosh Classic II with no sound. Analog board issue?


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I have a Mac Classic II that has no sound. I recapped the logic board but no luck. However, I tried the board in my Mac Classic and the sound came straight on!

 

My question is, does the analog board have anything to do with generating sound (is it an amp)? And if so, is it likely to be the caps on that?

 

Anything else I could try?

 

Just asking before I dismantle it all as removing the tube and analog board is a bit of a longer job :)

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The Classic and Classic II use the same right? I found this on page 18 of the Classic 1 dev note:

https://cdn.preterhuman.net/texts/computing/apple_hardware_devnotes/Mac Classic.pdf

 

 

Pin number      Signal Signal       Description
1               +12V                +12 volts
2               +5V                 +5 volts
3               +5V                 +5 volts
4               /VSYNC              Vertical synchronization
5               /HSYNC              Horizontal synchronization
6               VIDOUT              Video output
7               SND                 Sound signal
8               –12V                –12 volts
9               PWM                 Brightness control signal
10              GND                 Ground
11              GND                 Ground
12              GND                 Ground
13              GND                 Ground
14              GND                 Ground

 

Are you getting anything on the line out port?

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  • 1 month later...

I had the same problem. The voice coil of the speaker itself was broken. It should read around 60 ohms with a multimeter. After swapping the speaker sound worked fine. It’s a bit of a pain to swap because there are metal rivets holding it in place. I used needle nose pliers to smush them on the top side of the board and wiggle them out from the bottom side. I used some cut rubber as posts to hold the speaker in place and hot glue on top to secure them a bit better. 

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