It's been a while since I gave an update on this. Getting parts from China is a great test of patience
I replaced the two electrolytic capacitors, the small green ceramic capacitor and all diodes. Didn't help.
I ordered the LM1819N chip, it got here today, replaced it. Didn't help.
I may try to poke around it some more but I don't know what else to try. I may just leave it. One of my friends suggested making a new digital tacho from scratch as a little project so I may just do that too
