Williams Stellar Wars display issues

20eyes

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My player 1 display is missing every other digit. All other players are blank. I tested all 4 displays and all work the same when hooked to player 1. I started re seating the connectors on the main display boardand when i unhooked the connector on the lower left hand side (leading from what looks to be the mpu board) all 4 player displays flashing 0's with every other digit missing.
The main display only has a 0 on the right side of the display if that means anything.
Im trying to check all the basics first. Im going to check voltages next. Just not sure if this is any sort of indicator of anything.
And holy crap is there heat coming out that back box, shouldn't there be a fan in there? It has a nice ozoney smell to it too.
 
I'm following the pinrepair archive. Tested voltages and all came out within range. And resoldered all the pins on the power board since half of them were cracked. Blanking signal has 5 volts. Tested UDN's on the main display board with the diode test method and found a UDN6184A that had a couple open readings where it shouldn't be open. Im going to replace that and go from there.
I also found the display output PIA on the mpu board was replaced with a 6821 apparently not a new problem.
If that doesn't solve it i'm not sure I want to tackle the display board. I have a feeling the driver board is the problem since its marked as having been repaired already.
 
You likely have issues on your master display board. Look at all the large 1/2 W 100k resistors. Are any of them blackened/open?

Chris
 
I found a bad UDN6184A on the main display board and replaced it with a 6118 also found a broken trace on the display board.
I also had a bad transistor and resistor on the driver board from a shorted coil and replaced the interconnect.

I finally got the last part i needed yesterday and I put the boards back in and now all the displays come up now except player 1 and 3 are missing the first 0.

Now it looks like its coming up in attract mode with all the playfield lights flashing and it wont coin up.
 
I finally got around to working on this again today. Resistors are all good so I swapped out the 4069 chip in the lower right corner nearest the 6118 that i had replaced on the master display board and now all the displays are fully working. Success! With any luck they will continue to work.
Now on to getting the machine to put the ball in play when the machine is credited.
 
So I finally got back to working on this. I replaced a coil and finally played my first game
on this machine. After several plays i've now got a flickering 1st digit on 1 + 3 displays looks like it could be a 74154 on the cpu board but I think ill test some udns first.
Then I can go on to still trying to fix the triple drop bank that doesn't work and the sound and the....
 
I finally found the source for the flickering 1st digit on the P1+P3 displays. I swapped the 74154 out and replaced a scanbe socket on another chip with no change and then found a cracked trace on the MPU board causing the flickering displays.
 
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