Checkpoint fixed

[BMHouze]

As I am now in the high voltage section and my tech buddy has little experience with DMD repair I could really use some help tracking down my last issue (that made me pull it off the market)
Backgroumd: when I got this machine at auction the dmd didn't work. This was identified as a blown 33k 1/2 watt diode in the dmd. My tech didn't habe the xact ome but we did chain a few together and it worked fine.
Now I have an intermittent issue with the dmd getting garbled. Turns on and shows checkpoint, software version then sometimes goes. Can play for a few games and it will go out (black no signal at all) mid game. Had it come back on to enter my initials.
Just don't know where to start looking. The dmd or the controller board. I have left the machine on without playong it for a few hours and the dmd was fine.
Thanks for any and all help
Brad

 

[sylvain]

Yeah, as per Clay's Data East Pinball Repair, that R95, a 33K 1/2 watt Resistor (not a diode) sometimes goes open or drifts in value.
Make sure your tech actually placed a 33K resistor there, not a diode.

Then, check the ribbon cable (with the power OFF, reseat it a few times on both ends).
Finally, with the power on, carefully check voltages arriving on the DMD board (+5, +12, +68, -98, -100),
as an intermittent connection or power supply could cause issues too.

Regards,
- Sylvain.

 

[BMHouze]

Yeah, I just finished reading pinwiki.com data east sega repair guides.
4.10.4.1
Sometimes this display will light but the display will appear garbled. The display will flicker and move but the output will not be readable. This can be caused by the R95 resistor on the DMD controller board going out of spec. It should be a 33K 1/2 watt resistor.
So it appears that the resistor that he put together with a bunch of others to get to 33K has failed. He has already built me a spare from 3 resistors. I guess I better hold out and get the proper resistor for the job.
Now I just have to get into the city to get parts.
I will have my tech do the other voltage checks suggested.
Thanks, Brad

 

[sylvain]

Hopefully the traces were not damaged at and around the R95 pads on the board...
Is this tech experienced in pinball and board repairs ?

- Sylvain.

 

[BMHouze]

Its been a few years out of the arcade back room.
Hes doing macro soldering fixing. Ipods and such for kicks.
We were careful and soldered to the wires of the removed one.
I get some of the lingo mixed up. I never took electricity shop and when he describes what is wrong it's like he is speaking another language.
So probably the string of resistors has a weak one or two. It is certainly acting differently than when it was blown out. I do believe it was not exactly 33k but a bit higher.

 

[BMHouze]

My tech buddy is suggesting that I could use a 33k 1 watt resistor if I can"t find the half watt. He claims that the 1 watt will be able to handle the voltages better.
I think I will hold out and see if I can get 2 of the correct one. I am a bit leery about where any of the excess voltage might go.

 

[sylvain]

Your tech is correct here.
33K 1 watt resistor would be physically a bit bigger, but would be a perfect replacement.
Much better than a string of resistors hack added in series to try to make the total value 33K...

This has nothing with 'excess voltage', but has all to do with the resistor operating temperature
and wattage/heat dissipation capability...

 

[BMHouze]

Then I guess I will seek out the 1 watt resistor to give the dmd the best chance of lasting long.
I want to be sure when I am ready to move on from Checkpoint that it has the best chance of being issue free for a long time.

 

[BMHouze]

I mustered up the courage to try to swap out the resistor myself. I only have a big ass soldering gun but somehow managed to do it. I put the dmd at 90 degrees in case of any drips.
I also swapped in a new coil in the slingshot that I previously had streched the swelling out of the sleeve.
Now all my issues are cosmetic.
Well aftet I playtest a bit

 

[BMHouze]

I was in the GTA and stopped at Starburst and got a new rottendogg power supply board.
Went to remove the original. What a mess. Some of it is hard wired in.
Damn, now I need to have my tech by.
So much for playing....

 

[BMHouze]

The back of the old power board

 

[BMHouze]

Its coming back from my techs house this weekend after his kids give it a good playtest for a few days.
Dmd problems were being caused by the quartz controller that is located right beside the ribbon cable conmection. Looks like it may have been getting grounded out from some movement during all the installation and removal.