Pinball The Shadow : How to check a defect Switch 53 Mon(g)ol

Fail on Switch 53 Mon(g)ol target 

What to check
Connectors 
J1xx = Power Driver Board
J2xx = CPU Board
J3xx = Dot Matrix Cotnroller Board
J4xx = Fliptronic II Board 

Switch 53 - Mon(g)ol target
33 Inner Sanctum
43 Through 3

Colum 5, Green Black, J207-5, U20-14 (ULN2803)

Check R72 1K Ohm
Check C16, 470pf
Check U20 ULN2803, pin 14
Check U14, LS3645C, pin 5

On WPC-S CPU boards, the ULN2803 chip is underneath the battery sub-board.
 ULN2803 is equivalent to NTE2018. 
If U20 dies "hard", it could also blow the 74LS374 at U14 
(on WPC-95 it's U23, a 74HC237) on the CPU board. 

Row 3 White Orange J209-3, U18-5 (LM339?)

Check D5, 1N4148
Check C5, 470pf
Check R56 2K? (vergleiche 54)
Check R55 1K
Check U18, LM339, pin 7

Check Diode Playfield 1N4004

Green ---o \o---|<=---white


Testing a Blade/Leaf Switch's Diode.

    Leave the leaf switch's diode and all wires connected.
    Make sure the switch isn't activated.
    Put the DMM on diode setting.
    Connect the black lead of the DMM to the diode's banded side, and the red lead to the non-banded side.
    A reading of .4 to .6 on the meter should be seen.
    Reverse the DMM's leads (red lead to the diode's banded side). A null meter reading should be indicated. 



Nice links
https://hansbalk.home.xs4all.nl/rep/sys11/index3.htm
https://hansbalk.home.xs4all.nl/rep/
http://techniek.flipperwinkel.nl/wpc/index2.htm#switch
http://theshadowpinballshop.blogspot.com/