My O-R-B-S drop targets weren ' t comin back up . So , i changed the TIP102 at Q2 since it seemed to be defect after being checked . The problem came back just after a few games . The original MPU  had been refurbished , in order to end up with an ultimate MUP as a spare one . I got the ultimate back on and the targets work fine with it .

Any ideas what can be wrong with the original MPU ???  

Thank you .

Claude

Only one solenoid not working?

Are the drop targets not resetting at game start as well,
or only during game play (and a drop not scoring) ?

If only during game play, make sure the DT switch contacts are
properly adjusted and cleaned with a business card, so that
the MPU 'knows' to reset them when they are detected all down.

Also make sure the sol.driver has no cold solder joints under the
header pins nor a broken female pin in the connector.

Cooke and I have seen a few cases where there is an intermittent
diode just ahead of the driver transistor (Q2 for you) causing this.

Finally, make sure there are no cold solder joints at the header pins
nor bad 0.100 pins for the J2 connector on the MPU.

(as you can see, I am not yet convinced that the issue is with your MPU!).

Bonne chance !
- Sylvain.

Could be the diode / intermitent factor , since it came back OK after changinc the transistor and switching MUP  at the second time . I ' ll go true your suggestions , starting with the diode .

Thanks Sylvain ...