Bram Stoker’s Dracula – DMD Driver Board Repair
Whilst the rest of the Bram Stoker Dracula repair needs to be written up – one of the ongoing issues as you can see below was a flaring DMD – this was making the display look absolutely awful. Even on startup the issue was present and whilst the game was playable – it didn’t look all that great; after all, pinball is all about the look and feel of a game and when something like the DMD being like this, it wasn’t enjoyable to play.
The DMD is driven by the DMD driver board (the top right board on this era of game, with 3 ribbon cables going to it, including one directly to the DMD). As per PinWiki (which I won’t link to as it is currently asking to download some weird flash update, which is a bit suspect) the voltages at the board should be as follows:
|Function||Pin||Spec||Nominal WPC voltage||Notes|
|Anode||1||-110V||-112V||-124V in early DMD machines|
|12VDC Offset||2||-98V||-100V||Must be 12V less than anode voltage. Will be about 20V less than anode voltage if display not connected|
|Cathode||8||75V||62V||Williams runs this voltage low|
Straight off the bat with the fist pin (the anode) there was an issue, the voltage being far too out of spec. Where the nominal voltage for this era of game would generally be -112V; this WPC DMD Driver Board was reading -148V – so yes, just slightly out of specification. Testing the incoming voltages showed that there was an on board issue as they checked out to the correct voltages.
When I got the board off, and actually had a physical look, it became apparent quickly what the issues were. Someone had “had a go” at this board before. What I found particularly amusing was, that where the tracks on the component side of the board had gone, as well as where the previous person had – or the game in it’s burning had… taken out tracks and pads throughout the area. It was also decided for some reason that the component side of the board wasn’t a good side of the board for components. In fairness though, it was working just not correctly.
The old components had to come off of the Dot Matrix Display driver board to allow me to fully assess what the extent of the issues were. Lots of burning around the area, although I didn’t take a picture were from a nicely charred resistor also. The tracks needed cleaning to ascertain what tracks were still intact and to remove any flux and dirt etc. and see what is there to be worked with before moving on to buzzing through the traces with a continuity tester on the meter.
After cleaning up the topside as best as possible, starting with Q6 I repopulated the components – working down through the components buzzing out the top and bottom side traces, I repaired each of the traces with new “jumper” traces. Some of the components pads were so far gone the soldering is a blob to hold the component to the board – it is messy, but unfortunately, it is working with what is left.
The bottom side with the jumper wires isn’t as you would like to see it, but it is a darn site better than what was there before. Using insulated wire ensure that some of the tighter jumpers don’t touch areas and short where it shouldn’t.
It might not have been the prettiest of repairs, but it keeps the original board in the game, instead of swapping out with a repro dmd driver board, and the game looks so much better for it.
Just another pinball repair when you go into the fix, thinking that it will be fairly straightforward. Once diagnosed to take off the components and swap out for known good parts would have been a nice and simple job, unfortunately – this took much longer to complete, simply because of the prior work that had gone considerably awry.