Niki Posted July 13, 2013 Share Posted July 13, 2013 I have a Colecovision with a no sound problem. The video is perfect, it just doesn't have any sound. Occasionally, I will get a buzzing static-y sound, not with any particular game. I have tested it on multiple TVs all of which work with my friend's colecovision and I have verified that all my cables work. One odd thing is that I have the expansion module to play Atari games on it and the sound works perfectly on the Atari games I put in there. (Not sure if the expansion module has it's own sound chip...?) My first instinct is that it is the sound chip, SN76489AN, but I would like additional feedback from anyone who might have more experience with this kind of issue before tracking down obsolete parts from china that I may not need. I have soldering/desoldering experience and some general electronics knowledge, but not a whole lot. Any help would be greatly appreciated. Thank you. Quote Link to comment Share on other sites More sharing options...
+nanochess Posted July 13, 2013 Share Posted July 13, 2013 It's easy to check if the sound chip works, use small headphones in pin 7 of SN76489AN. http://es.wikipedia.org/wiki/Texas_Instruments_SN76489 Also with a logic tester check if pin 6 and 5 goes active to low and if there is clock in pin 14. 1 Quote Link to comment Share on other sites More sharing options...
Niki Posted July 13, 2013 Author Share Posted July 13, 2013 (edited) Thank you for the response. I attempted to use some small headphones on pin 7 and I did not get anything. The Logic tester goes active to high on both pin 5 and 6, Pin 14 goes to low. So, does that mean the the chip is bad or are there other things I should check first before ordering parts? Edited July 13, 2013 by Niki Quote Link to comment Share on other sites More sharing options...
+nanochess Posted July 13, 2013 Share Posted July 13, 2013 Thank you for the response. I attempted to use some small headphones on pin 7 and I did not get anything. The Logic tester goes active to high on both pin 5 and 6, Pin 14 goes to low. So, does that mean the the chip is bad or are there other things I should check first before ordering parts? When you put a game and the music is playing, the pins 5 and 6 should be ticking to low (74LS138 generating selection) and pin 14 should be changing continuosly (you can measure a frequency of 3.58 mhz here) Of course, you need a logic tester that can detect pulses. In any case if everything else is working fine then it's 90% sure that the chip is bad. By the way, the schematics http://www.atarihq.com/danb/files/colecovision.pdf Quote Link to comment Share on other sites More sharing options...
Niki Posted July 13, 2013 Author Share Posted July 13, 2013 Thank you so much for all of your help! I'll order the part right away. Quote Link to comment Share on other sites More sharing options...
+nanochess Posted July 13, 2013 Share Posted July 13, 2013 Thank you so much for all of your help! I'll order the part right away. I'm glad of being able to help you. Quote Link to comment Share on other sites More sharing options...
channelmaniac Posted July 28, 2013 Share Posted July 28, 2013 I have a couple of tubes of these chips, just don't have them up on the website yet... but, good luck ordering from China. Too many counterfeits... Quote Link to comment Share on other sites More sharing options...
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