[sdiy] Prophet 5 Rev3 RAM issues

[Roman Sowa]

Try adding supervisory circuit between CPU CS line and memory CS input. 
It will block any spurious pulses that may appear during power up and 
power down. Most probably those transients are writing some rubbish to 
RAM every time you switch the synth off.
A chip like that also switches supply line between synth power supply 
and battery, much better than usuall diodes. All based on 5V line going 
down.
Example ADM691A from Analog Devices.

Roman

W dniu 2015-09-20 o 23:17, John Henson pisze:
> I have two Rev3.0 Prophet 5's here right now with bad 6508's in the
> battery backed up RAM, the availability of these chips is low and the
> costs very high, I built a piggyback board to use a 6116LP chip but
> while it mostly worked, the memory timings must not have been quite
> right as random bits got changed, I tied CS to ground and OE/ to the
> Chip enable from the original system, should I try this the other way
> around, and has anyone else out there had to do this?
>
> John,
> www.retroactivesynth.com
>
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