K10042 cluster woes

Ok guys. Here goes. Im almost done dealing with this garbage. Ive had my cluster out 100 times.

It starts with a 90 240 m47. Odo stopped working, so i put in a tach and a new speedo with a good odo gear. Odo still doesnt work.
Now the left illumination bulb doesnt light up, and odo doesnt work. The bulb is known good.

Any idead whats wrong here?

Thanks

Very interested in hearing an answer to this..in-law's '92 240 has the same exact issue, aside from the Tach - no Tach in theirs. So that eliminates one guess.

Same thing with the one bulb?

Yep - left side instrument cluster light is off, but the bulb is fine. Odometer isn't working, even with a new gear.

May need to reflow some solder joints - just haven't had time to look too deeply into it.

Bench test bulb. Voltage test bulb circuit.

Odo is driven by speedo, so problem must lie in speedo unit.

Oh, so much woe...