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

[Gavin Muir]

Hi Michael & All,

> 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).

	This is what stumps me as well. When I first got the unit, there was 
one screwy program, but I think that was the previous owner's doing. It 
has held programs without fail ever since.

> A dying battery would affect all data, not just the MIDI parameters.  
> I don't
> have MKS-70 schematics handy, but I wonder if it has separate RAM 
> chips for
> the voice patches and for the global stuff (the MIDI params, etc.).  
> How many
> SRAM chips are in there on the CPU board?  I might suspect that one of 
> them is
> bad.  Do you have a schematic set?

	Unfortunately the only set I have are the service notes available on 
the internet. The RAM chips are on the "Assigner" board with the CPU, 
but the images are not clear enough to really identify what's going on 
(and I must admit, my ability to read schematics, particularly in 
digital circuitry, is pretty weak).

	From what I can see, there are 2 CMOS RAM chips, and one other static 
ram (the latter I haven't been able to locate in the schems). Aaargh! 
Time to call Roland for the real deal!

	One thing I did notice in the power supply is that there is an EMI 
board on the mains input, which could play into the spike theory, but 
again, it's a spike with surgical precision if it is!!!

Gavin.
>
> Michael Bacich
>