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

[greg montalbano]

The battery would of course be a good place to start (& easily checked).

If that doesn't do it, there's also the "power on detect" circuit -- synths 
with  battery-backed memory have a little protection circuit, to prevent 
power up spikes from causing this very problem (the scrambling usually 
happens on power on, not power down)   (had a similar situation with my 
Prophet 5 -- turned out not to be the battery OR the RAM, but a faulty 
transformer sending a spike that got through the protection circuitry & 
scrambling some  -- but not ALL -- of the RAM every time I powered it on).

Take a look at your power supply schematics, and trace through that circuit --
do some measurements & see if anything jumps out at you.

~GMM


At 05:10 PM 2/3/04 -0500, Gavin wrote:
>Hi all,
>
>A DIY repair question.... ;-)
>
>I'm just getting around to cleaning up the SuperJX I picked up last 
>summer, and as far as I can tell it is
>fully functional except for one ANNOYING feature.
>
>Every time I shut the machine down, the MIDI parameters get scrambled. For 
>example, the control
>channel becomes 1X (literally what the machine reads!!), and I get 
>similarly odd results on both the
>individual A and B channels. While I CAN go through this little routine 
>upon startup forever and ever, I
>am generally concerned that this might signal a bigger problem on the horizon.
>
>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.
>
>BTW, if I recall correctly I'm on version 1.04 (which I plan on upgrading 
>soon in any event).
>
>Any other ideas?
>
>Cheers and thanks!
>
>Gavin.