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Aaron Spinks

Colecovision still no sound, new sound chip

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Ok I need some help. I replaced my sound chip on my colecovision and still cannot get sound from pin 7 on the chip. I soldered a socket in and put a new sn76489an in. Testing the DC voltage on pins 5 and 6 I get 3.75. Testing AC on pin 7 it fluctuates from 1 to 3. This is all tested with the power on and frogger running. Any suggestions? I am running the retrofixes av mod.

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Where are you tapping your sound signal from?  All I see hooked up in the pics is composite, Ground and 12 volts on the RF module.

Edited by Ruggers Customs

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It's good that pin 7 is now doing something.  But now you have to hook it to an RCA connector so that you can get sound to the TV.  A good place to tap sound is the C88 capacitor above U15 near the RF box.  Connect to the left side.  You'll also need to connect the RCA's ground to something grounded on the board.  For instance, it could connect to the video connector's ground.

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I have tried tapping the sound from pin 7 on the sound chip and the left leg of c88. I am simply touching the wire to these points as I do not want to solder until I know I get sound.  Should i try to just solder it to c88 or pin 7? The rca is grounded with the video on the ground in the rf box.  Should I ground it separately? 

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31 minutes ago, Aaron Spinks said:

I have tried tapping the sound from pin 7 on the sound chip and the left leg of c88. I am simply touching the wire to these points as I do not want to solder until I know I get sound.  Should i try to just solder it to c88 or pin 7? The rca is grounded with the video on the ground in the rf box.  Should I ground it separately? 

Don't tap it from the chip directly.  If you do then you won't have sound for your atari module.  Tap it from c88 or from pin header 2 on the RF box.  Your grounding should be fine as is. 

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Edited by Ruggers Customs

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I tried tapping it on that 2nd pin as well.  No luck still... I am baffled at this point why I wouldn't get sound. Should I solder it to that pin or leg? Right now I am just touching the tinned wire to it. 

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If it were me I would temporarily solder the audio wire to pin 7 on the audio chip just to make sure you're getting sound from the new chip.    If so then remove the wire from pin 7 and solder it to one of the two other points.  If you're not getting sound at either c88 or the pin header 2 then there's a fault somewhere in the circuit from the chip onward.  Then it's just a matter of breaking out a multimeter and tracing the fault.

Edited by Ruggers Customs

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Ok.  I'll give that a try when I get home from work.  Let's say I don't get sound from pin 7 when i temp solder it,  what would i check then?  

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Just a thought,  is it possible the issue is the wire?  Most rca cables are thick and the wire that came with the mod kit is not as thick. 

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You can always test that the wire has continuity with the center of the plug.  A simple multimeter would tell you that much.  Then make sure it's not shorted to ground.  Check both audio jacks just to make sure.  You can also test that there is a connection between C88 and pin 7, but you have to test that in ohms mode because it goes through a resistor and won't be a direct connection.

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So I soldered the audio to pin 7 and I have sound! I don't plan on using the Atari module so I'll leave it there.  I only plan on using the super game module. Thanks for the help!

Edited by Aaron Spinks

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On 11/19/2019 at 5:55 PM, Aaron Spinks said:

So I soldered the audio to pin 7 and I have sound! I don't plan on using the Atari module so I'll leave it there.  I only plan on using the super game module. Thanks for the help!

Super Game module audio will also be low if you don't tap C88.

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