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Thread: Apple IIgs with Quiet sound output.

  1. #1
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    Default Apple IIgs with Quiet sound output.

    My Rom 03 apple IIgs has been getting very quiet in the past year. I have the volume control all the way up at this point in the GS options. I have tried other known good speakers; same result. What could be the problem?

    edit: Headphone jack/audio out works fine on back of unit.

  2. #2
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    Off the top of my head, I would say caps giving out. I would carefully recap it, for openers.

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    Sorry should have mentioned that. Already recapped all electrolytics on the board no difference at all. PSU also had most of the electrolytics replaced, but tried other psu and same issue.

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    Wait, I didn't read properly anyway. So the jack out the back is fine, but the speaker inside is quiet? I would think the amp would not "weaken" but anything is possible I suppose.

    The IIGS uses an LM380 amplifier IC. The old IIgs has the 8-pin DIP version of the IC in a socket located at the front of the main board near the DOC sound chip. The sound from the DOC also goes through several op-amps.

  5. #5
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    The Internal speaker sounds very quiet.. When its at 100% it sounds like 20% on a healthy unit. When I connect speakers/headphones to the rear jack they sound completely fine..
    Last edited by VERAULT; December 30th, 2019 at 03:08 PM.

  6. #6
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    Quote Originally Posted by VERAULT View Post
    The Internal speaker sounds very quiet.. When its at 100% it sounds like 20% on a healthy unit. When I connect speakers/headphones to the rear jack they sound completely fine..
    Have you tried disconnecting and reconnecting the speaker connector from the motherboard? Perhaps there is some corrosion on the connector pins.

  7. #7
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    Quote Originally Posted by cruff View Post
    Have you tried disconnecting and reconnecting the speaker connector from the motherboard? Perhaps there is some corrosion on the connector pins.
    Yes i have and cleaned the header pins. No change. Im leaning towards a resistor at this point.

  8. #8
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    If UM11 (LM380) was weak for some reason, you would likely get reasonable volume in headphones but not the speaker.

    You could test SR74 (1K) and SR75 (560) to see if they have their proper values, if either of those were shorted or had much lower values, that would reduce the speaker output.

    The signal to the speaker goes through the headphone jack which disconnects it if a plug is inserted. If those contacts are oxidized or corroded, that would also reduce the signal to the speaker. You could test it by connecting the speaker between the audio ground (J17 pin 2) and the junction of SC6 (22 uF) and SR12 (220), bypassing the headphone jack.

  9. #9
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    Thank you cruff, these are some great tests and exactly what I was looking for. Will give a try tomorrow!

  10. #10
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    Quote Originally Posted by VERAULT View Post
    Thank you cruff, these are some great tests and exactly what I was looking for. Will give a try tomorrow!
    Actually forgot it was new years eve.. Better give me a day or two to try those checks!

    Happy New Years everyone!

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