[sdiy] Weird Prophet 600 issue

[Dale Marvin]

On 2/18/15 11:14 AM, Travis Thatcher wrote:

> .... We started probing things with a scope and
> traced around U107 - the 4174 Hex Latch. The chip in there was
> a CD40174 and we replaced it hoping that could help but no dice. We
> noticed that pin 7 and pin 10 are the enable signals for the mux for
> each pcb with the controls. The duty cycle for the mux on the right
> board is way wider than the duty cycle for the one on the left board
>....

The pot scanning on the p600 is software adaptive such that most/all of 
the time is focused on what's moving. The Bend & Mod wheels are always 
scanned regardless of whats going on with the front panel.

I worked on one once that had functional Bend & Mod but was completely 
dead on the panel. Problem was caused by one bad pot that was very noisy 
and using all the scan time.

Check for dirty/noisy/bad pots ...

-Dale