NSM ES6 100 CD Jukebox Troubleshooting

[Sidfaber]

Hi all! First post here but I’ve been watching this forum for years. Looking for any advice or suggestions on how to troubleshoot an NSM ESVI central board. 

Here’s the problem:  I have two identical units that don’t display anything on the LCD screen.  One was working for about an hour before it quit.  I can’t find any technical manuals online, only the operators manuals that came with the machines and show basic connections. No detailed schematics or troubleshooting. Looks like these boxes were pulled from service around 2005-2010.

What I’ve tried so far:  I replaced the M48T35 timekeeper chip and its Snaphat battery. I mapped out all the ICs and measuring points on the board.  Voltages seem good (+5 reads 5.24v), cpu clock is good, I can see data transfer between the CPU and the flash memory.

The LCD should get clock and data from a serial bus that I’ve mapped back to output pins on the CPU, but they’re both always high.

Any suggestions on where to go next? Happy to share what I’ve mapped on the board so far if anyone’s interested. Thanks in advance!!!