First post, by Kahenraz
This thread is a follow-up on a post I made elsewhere:
Kahenraz wrote on 2022-01-17, 23:35:
It seems that there is something else wrong with my SC-55mkII. I knew it sounded strange but now that I have a collection of recordings, I can finally pin it down. It's completely off-pitch! This isn't an issue with just Duke Nukem 3D. The pitch is wrong with anything it plays.
Here are comparisons with my SC-55 (V1.21), SC-55ST and SC-7. The SC-55ST and SC-7 are derived from the mkII and should sound the same but instead they sound much closer to the original SC-55.
Also mentioned in the other thread was the discovery of damage to traces on the board. This damage appeared unrelated and did not affect functionality that I could tell; I only use a limited subset of the device to play music from video games.
After my repair I found that it continued to play out of tune. While troubleshooting this I discovered it to be some kind of a bug with this particular board or firmware revision. I remove the coin cell batteries in all of my synthesizers to avoid any chance of corrosion and this was an unexpected side effect.
For this unit, power cycling without a battery will cause the synthesizer to be out of tune. Manually resetting the device using the buttons on the front panel after powering it on will fix this problem but it will detune again after the next power reset. Keeping a coin cell battery installed will retain the correct tuning between power cycles. A front panel reset must be done after installing a new battery; simply installing a battery will not fix the problem.
It's interesting that retuning the device is successful only by the front panel. Sending a GS/GM reset SysEx command will NOT fix the tuning problem.
My mainboard revision is 7543605000 and the ROM firmware is version 1.00. I've included photos of these as well.
See attached for some example recordings.