Analogue-sequencer

Steve, 

> The original display burned out and so I replaced with the 
> blue/white LCD.  After replacement, the P3 no longer works.  
> The display lights up, but the machine fails to boot.
> 
> Before installing this, it was running OS 3.00?   No Mem-X 
> expansion.  It ran fine--- for an hour.  After approximately 
> an hour, the button response would slow down.  The MIDI 
> wouldn't drop out, just the refresh rate of the LEDs and 
> buttons would slow down dramatically.  Never figured this one out..?

Since the behaviour has changed with a change of display, I would suspect
the problem here is with the transistor that drives the enable line for the
display - Q1.
If the transistor used has particularly low gain, then it can fail to drive
the enable line properly.
The fix is to decrease the size of R20 from 22k to 10k, increasing the drive
to the base.
There have been a few cases where a P3 display failed to work, and this
change has got them going.
It could be the transistor was marginal with the PLED, hence the fault not
appearing until after a warm-up period.
I know the enable lines on the LCD modules are more likely to show up this
problem than on the PLED.

Best regards,
Colin Fraser
Sequentix Music Systems Ltd
http://www.sequentix.com