The DMD, Part V

I tested the DMD board today. It was over in i second. I turned the machine on and the R5 resistor exploded.

I'm running seriously low on ideas now.

The DMD, Part IV

I was finally able to get back to my White Water this weekend. Of course, my primary goal is still to get the DMD controller back into working state. I just picked up the controller and some tools and took it back here with me

Here's the approach I'm taking now.


On the left, there is a broken White Water's controller and on the right the Star treks, that is all fine and dandy.

I measured the resistance of all the components and all the traces on both boards and try to identify any suspicious components, that might be causing too high negative voltages.

Anyway, the following measured quite different than on the working board: D4, D5 and D7 diodes. Q4, Q5 and Q6 transistors and R3, R4 and R6 resistors. These are the things I'll replace.

I guess I'm going shopping tomorrow. Naturally I will report about the results.

The DMD, Part III

The DMD controller failed again yesterday. This time it went with a bang and scared the hell out of a friend playing the machine.

At first it seemed that only the fuse failed, but after replacing it, the display looked really really weird. No letters, no graphics, just some sort of huge blob in the middle. I measured the voltages (Again) and the two negative voltages were waaaaaay of the normal readings. They read -152/-130.


What am I going to do about this one? I don't know yet. I'll see in a couple of weeks, when I'm back with my Whitewater.

It seems that if things continue to evolve in this manner I'll have to start a new blog and dedicate it to DMD controller exclusively. :)

The DMD, Part II

I came back home today and naturally the first thing to do was to fire my whitewater.

To my surprise, here's what I found:

Now that's something that puts my soldering skills to trial. I started dealing with this issue immediately, so the first thing i did was to measure the voltages again. The two negative voltages were perfect this time (-118 and -106). The wrong one was +62 which read only 24 volts. Here's what pinrepair has to say about too low +62 voltage:

"The +62 volts is not +62 volts.
On WPC-S and earlier games, the positive DC voltage trace that comes from a very small bridge rectifier BR1 is physically routed underneath resistor R9 (1.8k 5 watt resistor). Because of the heat generated by this 5 watt resistor, and the current drawn from the bridge rectifier, this circuit board trace can become burnt and break underneath resistor R9. Because the trace physically runs under this resistor, the broken trace can be hard to see. "

And here's what my controller looked like:

Apparently this is exactly what happened to my board. I consulted the enclosed board schematics and here's the solution I came up with:

The DMD lightened up and I was really thrilled until I noticed that some sparks are flying around the board. It' seemed as that the cable I soldered on to the resistor was to close to the heat sink. I quickly turned the machine off. The board worked, so no other components were burned. I just had to replace the missing trace in some other way.

My second attempt looks like this:


And here's the result:

No sparks this time. I guess it's playing time again and let's see what the testing will bring.

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.