The DMD

The first to deal with on my journey of bringing White water back to life was its non working display. We all now that display is a important part of every pinball, but you can't really tell how important, until one is actually gone. Imagine. No self diagnostic, no error reports, no tests, no settings, no score, nothing. Anyway, it was obvious that this is going to be the first issue to address in order to move anywhere.

The symptoms.
The DMD was not completely dead. It showed some life, but only around the edges and even there it was barely lit (again, no picture :(). It seemed that picture was getting through, but there just wasn't enough power to display it.

The diagnostics
Luckily I still had my Star trek at hand (loaded and ready to transport), so naturally, the first thing I tried was plugging the White water's DMD into Star trek. The thing worked and a 180€ that a new display would have cost me was saved. Since the display itself was flawless, there was only one remaining option left. There had to be something wrong with the Dot Matrix controller. After re seating all the cables that come from the controller a couple of times didn't worked I grabbed my multimeter to measure the voltages that come from the controller which gave me some answers. The first two pins read only -75/-63v while it should be at least -115 / -103.
The reason for non working display therefore is: Too low negative voltage produced by the dot matrix controller.
At this point I had to leave for Ljubljana where I live and work, so I just packed the controller and some tools and took the stuff with me. Unfortunately it'll have to pass a couple of weeks before I'll be able to work on White water again, but at least I'll try to get the controller in order till then.

The cure
The problem was solved by rebuilding the enitire high voltage section of the DMD controller.
Here are some pics.

1. The DMD controller


2. The (faulty) high voltage section


3. The shopping list


4. Printout from pinrepair


5. The tools used


6. HV section without components :)


7. Garbage


8. and finally... freshly rebuild HV section



The test
It's a good thing that I recently moved my Star Trek here to Ljubljana, so I was able to test my four hour hard work.
Here's the result, after switching the controllers:
HOORAY! The thing works.

Let me add that this was my first real attempt at PCB soldering, so I'm really really proud about the result.


The thanks
www.pinrepair.com. I'd be doomed without this site.