(Topic ID: 314887)

Rottendog WPC MPU switch matrix issues

By arolden

1 year ago



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#1 1 year ago

Hi everyone

Having some switch matrix issues, hopefully someone can offer some input regarding troubleshooting.

I have a Demolition Man MPU from a friend which was severely affected by battery corrosion. He opted to buy a Rottendog MPU to replace it. I transferred the ASIC, processor and game ROM to the new MPU and have it in my own Demolition Man for testing. I am now having problems with the claw, which will appear to work normally before stopping and getting stuck at random points when moving left to right.

I figured out that it was stopping because the claw left (and sometimes the claw right) switches (switch 25 and 26, both opto switches) were sometimes registering while the claw was in the middle of moving from left to right or vice versa. Of course once one of these switches triggers, claw movement stops. The claw usually gets stuck at that point, and when I go into test mode, moving the claw will trigger the claw left or claw right optos as soon as I try to get it to move, making it stop again.

I have narrowed this issue down to the Rottendog MPU. The claw optos work perfectly with my original WPC MPU board in the game. I have also tried the following:
- Replaced U20
- Replaced game ROM
- Replaced ASIC
- Reflowed solder J207 and J209
- Reflowed solder on U20 socket
- Reflowed solder on U19
- Verified continuity from the column 2 and row 5 and 6 connectors to U14 and U13 respectively
- Verified 12v is present at U20 pin 10
- Verified resistors and diodes associated with column 2 and rows 5 and 6 test within spec

Not really sure where to go from here. I don't think it is a connector issue as other switches in these rows and columns work fine. I don't think it is an opto board issue as all other optos work fine. I don't think it is a power issue as other switches and 12v loads work fine.

Any help is appreciated!

#2 1 year ago

Here's a video of the problem.

1 week later
#3 1 year ago

This is now resolved. The problem was caused by the Color DMD. No idea why that was contributing to it, but as soon as I installed an original display, the issue went away. As soon as the Color DMD was reinstalled, the issue returned.

Everything worked fine with the original MPU and the Color DMD, but for some reason the Rottendog MPU doesn't like the Color DMD. I assume it has something to do with the 12v supply, but can't explain why the original MPU works while the Rottendog does not. Normally I would assume connectors, however I tried the Color DMD and original display a couple of times each, and the results were consistent.

#4 1 year ago

The opto brightness may have dimmed to the point it is right on the edge of what the detector can see. Extra load on the 12v reduces voltage and opto brightness. Voltage drop across connectors and leaky electrolytic cap on the opto board is leaking other things to look at.

#5 1 year ago
Quoted from barakandl:

The opto brightness may have dimmed to the point it is right on the edge of what the detector can see. Extra load on the 12v reduces voltage and opto brightness. Voltage drop across connectors and leaky electrolytic cap on the opto board is leaking other things to look at.

This makes sense however I don't understand how the problem disappears with the original MPU board. Does the Rottendog board pull more power from the 12v supply than the original board?

#6 1 year ago
Quoted from arolden:

This makes sense however I don't understand how the problem disappears with the original MPU board. Does the Rottendog board pull more power from the 12v supply than the original board?

I doubt that the MPU is drawing more from the 12V line. If anything I would suspect a small variation on parts in the switch matrix section where is only becomes a factor in cases like you see. From what I understand that is one of their better boards and usually just works. I'll have to take a closer look at that sometime.

#7 1 year ago

I've seen many issues with color dmd added to games. Almost better to give it it's own power source

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