[sdiy] Weird Prophet 600 issue

[gordonjcp at gjcp.net]

On Wed, Feb 18, 2015 at 02:14:33PM -0500, Travis Thatcher wrote:
> left board were written into RAM. I assume it was the mux kinda
> freaking out for a second during the disconnect but once the wires
> were connected the left side was still unresponsive. I'm wondering if
> its the MUX that is bad or if there's something else we should look
> at. Curious if anyone has a P600 and can check the waveforms at pin 7
> and 10 of U107.

Check the MUXes.  The select lines being switched assymetrically won't be a problem.  It's reading one MUX, reading the other MUX and then leaving the select lines alone while it gets on with the rest of its processing - no biggie.

If they are the usual 405x MUXes they fail just for the fun of it.

-- 
Gordonjcp MM0YEQ