Prologue problems

Tony Allgood oakley at
Sat May 16 23:25:57 CEST 1998

Hi all,

I wrote a little while back about my Prologue Midi-CV converter. It has two
problems... firstly, too much glide between the notes which cannot be turned
off. Now this I've sorted by using a better analogue switch, lower S/H cap
and better buffers. But the other problem has really come to a head now.
About three months ago, the unit would occasionally play notes for no
reason, it even sometimes would turn on all of its four gate outputs and
then sweep the CV output down to -15V over about a minute. Cool sounding,
but not what I wanted. Anyway, these faults began to get more and more
common and now, the unit is completely duffed up. The thing is this is a
digital hardware fault, the analogue stuff is fine, and don't now how to fix
it. Any ideas?? I don't want to send it back to the manufacturers, that
would be cheating. The processor is a Z80 with a 6850 doing the midi bit,
but I'm an analogue man... so I need some pointers. Thanks.

Tony Allgood, Cumbria, UK

e-mail: oakley at

My latest project; a rack mounted VCF module with warmth. PCB available

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