Macintosh Color Classic Internal Speaker Not Working

jmb2011

Member
Hello All,

Hoping to get some help with the internal speaker not working. I was testing a logic board that I recently bought as an extra to have on hand. So I swapped it into my color classic and bent a pin on the chassis connector due to a bent pin on the logic board. Long story short, I had to dissemble the Mac to get that pin back into shape.

Once reassembled, I turned the Color Classic on, the speaker let out an awful long drawn out whine (kind of like an LC that hasn’t been recapped yet), and then it hasn’t made a sound since.

Bit of background, the logic board has been cleaned and recapped, and so has the analog board. It’s been working fine (speaker included) until I had to take it apart tonight.

I have checked the speaker for resistance, and it’s coming back fine. I have checked the cable from the point it’s soldered on the analog board to the connector, and it’s getting continuity just fine. All the pins on the analog board connector looks great.

I also checked the grounding on the Rf shields, and they are all in continuity with each other and on the ground plane with the logic board and hard drive wiring harness ground ( I know sometimes grounding can be an issue).

I get sound out of the headphone jack just fine, so audio chipset is working. Just not the internal speaker.

Any ideas?? I’m at a loss here!
 

daanvdl

Well-known member
I would start by measuring with a scope on pin 2 of the TDA7052 for audiowaves, and check VCC to the TDA on pin 1. Double check continuity for ground pin 8.
 

jmb2011

Member
I would start by measuring with a scope on pin 2 of the TDA7052 for audiowaves, and check VCC to the TDA on pin 1. Double check continuity for ground pin 8.
Is this on the analog board or the logic board? I saw that it looks like it goes through an IC on the analog board?
 

daanvdl

Well-known member
The TDA is on the analog board. You have to start somewhere troubleshooting, and this is a easy to access spot which can be measured live. The TDA is the amplifier between the audiochip on the logicboard and the speaker. If there is no audio signal reaching the TDA suspect the logicboard, and visaversa. Also keep in mind there is a volumecontrol line from the LB to the TDA.
 
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chiptripper

Well-known member
I’ve had TDA7052s fail on me out of the blue.

Also, the front up-down volume control buttons can get pressure pinched during reassembly, so they continuously press up, down, or both at once.
 
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