@ drummerdimitri
I have a WX2 unit with a WXMP-MS, a WXP 120 and a WXMT-MS tweezer. Multiple tips for each.
A)
Let me know should you want me to make a few voltage or resistance measurements to compare to yours.
This might help your troubleshooting efforts.
B)
The weak point I found over the years is the main unit connector in the front and the wire going in the corresponding plug.
C)
Also keep in mind that removing and connecting tips while the power is applied can cause a failure. There is only a line in the user manual about this and no emphasis either.
This would not apply to the WXP 120 of course but an intermittent cable could.
Have not been able to secure a schematic diagram on this model either....
Good luck with it and keep us informed.