Repair Log STTNG Star Trek : The Next Generation Flipper Pinball DMD Display outage

Hey,

had yesterday some time to repair my pinball machine ST:TNG.

After doing some cleaning the DMD Display was not function anymore. No problem, I just replaced R6 and R13 on the DMD controller PCB.



:) Just kidding. Tons of reading, threads, tools buying later I was able to fix the problem.

Tools needed:

- Solder Iron
- Desoldering wick
- ESR Meter capacitor testing tool (Great Vid from Level42)
- Multimeter

Background Info:

WPC schematics manual Page 11
Kompedium Fehlersuche DMD Display, Page 13
ESR Meter

Testing steps :

Exchanged Display - still nothing

Step 1
Measured DMD Controller PCB
J604 -

- Pin1 to GND: -16V (should be -70V - -125V, mostly 114V)
- Pin2 to GND : -9V-10V(should be pin1 voltage level - 12V) (against Pin1 ca. 6V, but should be 12V)
- Pin 6,7,8 OK (5V, 12V, 62V)

Pin1 without DMD connected vs gNS about -40V

Apparently Pin1 and Pin2 voltage level are not correct

Step 2
So go ahead to
J605
80VAC between Pin1 and 2 -> OK
100VAC between Pin3 and 4 -> OK

Step 3
Measured Fuses -> OK

Step 4
Measured BR2 - Do measure R13 both ends voltage level, should be 130V -> OK

Step 5
So go ahead
Kompedium Fehlersuche DMD Display, Page 13

Check parts in Blue box.
Measured with ESR70 all capacitors, all ok.
Measured R6 and R13 -> Ups, some MEGAohm.

Replaced R6 and R13 with 68Kohm instead 47kOhm 1/2Watt, had no other ones in stock.

DMD Display works fine again.