[sdiy] Odd MKS-70 Behaviour....

[Colin f]

> > So far, the only things I can think of are:
> >
> > 1. The backup battery is on the way out;
> > 2. Bad RAM chip;
> > 3. Partially scrambled software. >>
> 
> I think it's odd that the MIDI parameters get messed up, but 
> the voice 
> programs don't (at least you didn't say anything about the 
> patches being damaged).  

Seems odd to me too.
The JX assigner board only has 1 RAM chip, so  bad battery should mean
lots of randomness.
It could be a bad power reset detection causing the RAM to get corrupted
during power off/on.
Another possibility is that it is an early MKS70 assigner which still
has the keyboard scanning gate array on it from the JX10.
The gate array shares the RAM with the CPU (it writes tables of note
on/off velocities into RAM, then interrupts the CPU to alert it to the
change). A bad array might be scrambling only certain locations.
Sounds like a fun fault to fix ;-)

Colin f