Location: Denver, Colorado
Symptoms: Wouldn’t make correct selections, if any.  Right channel sound was fuzzy.

I wasn’t able to obtain a service manual for the CMM4.  The closest thing available was a CMM1 manual, which ended up being of no help.  There were quite a few electrical differences in the mechanism, like different cam switches (CMM1 has 8 cam switches, CMM4 has 5 cam switches).  Also, the CMM4 has a tube amp and the CMM1 has a solid state amp.

The “write” side of the selector plate was working well.  The “read” side scanner would usually jump right over the selector pin, unless it was actuated by a pin on the outer ring. The pin reset solenoid wasn’t actuating.  Long story short, it turned out to be a bad stop switch.  The switch was reading many thousands of ohms when it should have been zero.  I drilled a hole into the side of the microswitch to try chemically cleaning it.  It helped bring the resistance down to about 180 ohms, but that’s was not good enough.  I found a compatible switch in my pinball parts and replaced it.  The jukebox made the correct selections after that.

The amplifier had a tube that looked bad.  Looking at it more closely, it had a crack in the glass at the base.  It was a 12AX7.  We used the tube from the left channel and the right channel started working.  The owner had a spare 12AX7 from a guitar amp that we used to get the amp fully working.

I also looked at the owner’s AMI G-120. It had a few minor problems that I was able to fix with some cleaning, adjustment and lubrication.