VOGONS


First post, by Axatax

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So, my SC-55 stopped producing sound. The front-panel lights up and shows MIDI activity but I can't get sound from the rear RCA jacks or the headphone connector. It appears to work, just no sound.

Before I go and replace it, is there anything obvious I can try? I've replaced the battery.

Reply 1 of 8, by keropi

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you need to open it and do a visual check ... maybe there are some cold solder joints on connectors ? though it does not explain why the display works and sound is missing
maybe some audio amp chip is dead

🎵Link to buy a PCMIDI mpu
🎧Orpheus soundcard project
💻WTB Amstrad PC7486SLC-33 system

Reply 2 of 8, by auron

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keropi wrote on 2020-07-04, 14:26:

maybe there are some cold solder joints on connectors ? though it does not explain why the display works and sound is missing

why not? cracked solder joints on audio connectors seems like the most common failure mode, if anything, and it wouldn't affect the display at all.

Reply 3 of 8, by keropi

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auron wrote on 2020-07-04, 20:47:
keropi wrote on 2020-07-04, 14:26:

maybe there are some cold solder joints on connectors ? though it does not explain why the display works and sound is missing

why not? cracked solder joints on audio connectors seems like the most common failure mode, if anything, and it wouldn't affect the display at all.

Only because OP mentions that both back jacks and front headphone connectors do not work, solder cracks on rca connectors for example do not affect the front one...
But maybe both are damaged, unless someone checks we can only guess

🎵Link to buy a PCMIDI mpu
🎧Orpheus soundcard project
💻WTB Amstrad PC7486SLC-33 system

Reply 4 of 8, by Axatax

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OK, I'm pretty sure this particular SC-55 is a lost cause, but --

I found the service manual online which I didn't know existed... I ran the sound tests, and I can get the tones and both demo tunes to play out of both jacks. Everything looks normal, but it won't play sound when it's coming from the MIDI IN jack, even though the display shows the MIDI activity, so I'm at a loss.

Reply 5 of 8, by Salient

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I think I have encountered the same issue way back once with my SC-55, but I managed to get it working again although I don't know exactly how.
I do know that I also did a factory reset by holding both INSTRUMENT buttons while turning it on. Have you tried that?

MIDI comparison website: << Wavetable.nl >>
(Always) looking for: Any Wavetable daughterboard, MIDI Module (GM/GS/XG)

Reply 6 of 8, by Axatax

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Salient wrote on 2020-09-25, 05:10:

I think I have encountered the same issue way back once with my SC-55, but I managed to get it working again although I don't know exactly how.
I do know that I also did a factory reset by holding both INSTRUMENT buttons while turning it on. Have you tried that?

I have, and this particular failure doesn't seem logical to me. It almost "seems" like something isn't set correctly. I went through all of the tests in the SM and they all pass.

Reply 7 of 8, by newtmonkey

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If you are using it connected to the gameport of a sound card, something may be muting the line in on the soundcard. I've noticed this with Might & Magic III/IV, but it may occur with other games? If you are using it on a modern PC with USB-MIDI, never mind 😀

Reply 8 of 8, by Shreddoc

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No specific technical knowledge to share, merely a logic : If we schematically consider a hardware device to be [Input Module] -> [Processing Module] -> [Output Module], then we could consider that the problem here may lie in the Input Module.