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Thread: Very odd Mega CD Model 1 Sound issue (Sounds out of tune)

  1. #16
    Hedgehog-in-Training Hedgehog-in-Training Eidolon's Avatar
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    Quote Originally Posted by Speedle View Post
    I will check the traces in that area as there is some cap leakage that could have damaged a trace. Failing that I'll replace the chip with the spares I have
    In my case, having had a similar problem, the problem could be solved by reflowing the solder connections of IC3, IC13 and IC14.

    This strange PCM sound symptom seems to happen when one of the RAM ICs (13/14) has a bad connection to the PCM chip (IC3).

    Some PCM music plays well, if the PCM samples are so small as to fit in one RAM IC only.
    The garbling only starts when both RAM chips are utilized.
    Last edited by Eidolon; 03-24-2017 at 04:58 AM.

  2. #17
    Video Game Modder Outrunner segasonicfan's Avatar
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    Quote Originally Posted by Eidolon View Post
    In my case, having had a similar problem, the problem could be solved by reflowing the solder connections of IC3, IC13 and IC14.

    This strange PCM sound symptom seems to happen when one of the RAM ICs (13/14) has a bad connection to the PCM chip (IC3).

    Some PCM music plays well, if the PCM samples are so small as to fit in one RAM IC only.
    The garbling only starts when both RAM chips are utilized.
    I had a similar problem recently and I was able to repair it. Yup, it was related to PCM RAM. I describe the repair in detail here:
    https://youtu.be/y8Xw1pkEHeA

    In my case it was a very odd issue indeed: the PCM RAM was missing a connecton on !OE, for no apparent reason..

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