Re: MUX_SH board mod tutorial
Posted: Oct 2nd, '20, 09:05
OK, Partia Success.
Edited... see additional text after original post...
Almost by accident, the problem where you still have sound, but the different MUX boards don't work (don't add accent, or don't appear to change the sound) on my v1.02 as above was fixed by... re-running the EEPROM initialisation!!!!
I was swapping out various ICs in an effort to see if anything worked and despite the EEPROM chip being fine, I put back an old one (when I first built this machine) and suddenly the accent was back for the instruments attached to IC111....
As I'd also swapped a few 595's at the same time, I put back the other EEPROM chip and it stopped working again. So I ran an init with the non working accent EEPROM and bingo, all working. So the init must do some kind of calibration associated with the MUX boards/accent voltages etc and needs to be re-run after you have swapped / changed / fixed / re-soldered your MUX boards....
I now have all 4 MUX working, in either slot - just need to re-init the EEPROM after swapping them around - I hope this helps someone in a similar situation and may explain a lot of the issues people have had, particulalry with mux in IC111.
Just to be clear, I didn't have the problem of muting, i.e. when the MUX were installed I still heard all instruments, just no accent noticeable on HC,RS,HH,CY
UPDATE... However...
After a few repeats of a pattern the accent slowly disappears. I think it actually is stuck on. So you hear no difference. Almost like the S&H gets so charged up that it never stops!
So resetting the EEPROM seems to only temporarily fix...
Meanwhile, my oshpark order of the mux lite boards arrived today and I've just had enough time to build one and its working perfectly, first time in 111. So I think there must be something in the tolerances of some builds that mean slot 111 is very susceptible. If you have issues like these I can recommend the lite boards as a potential fix. I ordered 6 boards, so have 2 spare if anyone wants to try. Even happy to build and test them in my machine and send assembled. Feel free to message.
Update2. So built 2 mux lite and have them both in this machine now. I was experiencing strangeness still, BD accent would cause HH to go quieter... scoped the output HH_ACCENT from the mux and could see it triggering fine. So confirming the mux boards were working. Also now the CP and RS were fine. Traced the accent circuit thinking 2SA798, removed tested all good, then finally after removing Q52, tested fine, and resoldering i thought I'd just double check TP1. 10.5v... what? It was bang on 5v last time I checked... I guess maybe the mux lite draw less? Anyway, adjusted down to 5v, reset EEPROM again and finally all accents working and stay working! Not sure if it was the TP1 adjustment or the resoldering of Q52. But combo of those and the mux lite and now two fully working machines!
Edited... see additional text after original post...
Almost by accident, the problem where you still have sound, but the different MUX boards don't work (don't add accent, or don't appear to change the sound) on my v1.02 as above was fixed by... re-running the EEPROM initialisation!!!!
I was swapping out various ICs in an effort to see if anything worked and despite the EEPROM chip being fine, I put back an old one (when I first built this machine) and suddenly the accent was back for the instruments attached to IC111....
As I'd also swapped a few 595's at the same time, I put back the other EEPROM chip and it stopped working again. So I ran an init with the non working accent EEPROM and bingo, all working. So the init must do some kind of calibration associated with the MUX boards/accent voltages etc and needs to be re-run after you have swapped / changed / fixed / re-soldered your MUX boards....
I now have all 4 MUX working, in either slot - just need to re-init the EEPROM after swapping them around - I hope this helps someone in a similar situation and may explain a lot of the issues people have had, particulalry with mux in IC111.
Just to be clear, I didn't have the problem of muting, i.e. when the MUX were installed I still heard all instruments, just no accent noticeable on HC,RS,HH,CY
UPDATE... However...
After a few repeats of a pattern the accent slowly disappears. I think it actually is stuck on. So you hear no difference. Almost like the S&H gets so charged up that it never stops!
So resetting the EEPROM seems to only temporarily fix...
Meanwhile, my oshpark order of the mux lite boards arrived today and I've just had enough time to build one and its working perfectly, first time in 111. So I think there must be something in the tolerances of some builds that mean slot 111 is very susceptible. If you have issues like these I can recommend the lite boards as a potential fix. I ordered 6 boards, so have 2 spare if anyone wants to try. Even happy to build and test them in my machine and send assembled. Feel free to message.
Update2. So built 2 mux lite and have them both in this machine now. I was experiencing strangeness still, BD accent would cause HH to go quieter... scoped the output HH_ACCENT from the mux and could see it triggering fine. So confirming the mux boards were working. Also now the CP and RS were fine. Traced the accent circuit thinking 2SA798, removed tested all good, then finally after removing Q52, tested fine, and resoldering i thought I'd just double check TP1. 10.5v... what? It was bang on 5v last time I checked... I guess maybe the mux lite draw less? Anyway, adjusted down to 5v, reset EEPROM again and finally all accents working and stay working! Not sure if it was the TP1 adjustment or the resoldering of Q52. But combo of those and the mux lite and now two fully working machines!