MCR Transformer Caps- Input issues???

tec9

Active member
Joined
Dec 25, 2006
Messages
2,111
Reaction score
23
Location
New Britain, Pennsylvania
Hey all-
I'm afraid as soon as I mention that this is a 4 player Demolition Derby, people will hit the back button!!! If you don't feel like reading my through this post, just check the question at the bottom.
I need some general advice on the MCR transformer caps. I've been having no luck repairing my 4 player Demolition Derby machine. Now I know not many people have this 4 player machine, so I'm just asking for some MCR advice in general. The problem I am having is with steering wheel controls. In game mode, the cars kinda randomly turn just a bit here and there...they don't go in constant circles or anything, but every once in awhile, the car turns a bit. I've been trying to figure this out, and haven't had much luck. When you turn the wheels the cars do turn, but when you are not turning the wheel, they kinda just randomly turn here and there...here is what I have done.
-swapped main PCB stack
-swapped around all of the optic boards, even tried spares on all the players.
-played around with different voltages on the rebuilt linear power supply
-swapped out the power supply with a MCR switcher from my test bench.
-Triple checked the wiring to the optic boards, and main board...even wrote down the pinouts, which seem to be non-existant in any manual or online.
-drank lots of beers and walked in circles cursing!

So as it stands right now..the game has the original/rebuilt power supply in it, and I feel I've swapped out everything except the large caps in the transformer/ suitcase assembly. Any chance that they could be causing this issue...I'm thinking it's possible because these opto boards get 5VDC and 12VDC, and perhaps the caps are allowing AC ripple through.

So has anybody replaced the big blue caps in a MCR game and have it solve input issues?
-Mark
 
When you turn the wheels the cars do turn, but when you are not turning the wheel, they kinda just randomly turn here and there...
Is there a self-test mode to check the wheel encoder? Usually you can spin the wheel to watch the position count up/down, or leave the wheel stationary and watch the position remain unchanged. This would be a good way to check what the game sees from the wheel inputs.

I'm guessing the self-test will demonstrate that your game sees encoder lines toggling (ie. position changing) even when the wheel is stationary. If so, then you can trace backwards and pinpoint the problem.

...and I feel I've swapped out everything except the large caps in the transformer/ suitcase assembly. Any chance that they could be causing this issue...I'm thinking it's possible because these opto boards get 5VDC and 12VDC, and perhaps the caps are allowing AC ripple through.
Bob Roberts sells them -- they're worth replacing but I doubt that this is a power issue. That circuit is not particularly power-sensitive so you'd have other symptoms first. You can rule this out entirely by using your oscilloscope (or DMM on AC) to check how much each power supply is rippling.
 
Thanks for the reply.....I forgot to mention that in test mode, the wheels seem to operate fine, except that if you push the start buttons rapidly, you will occasionally see the value of one of the wheels (random) change value for a split second then go right back to the position it was at. If you let the game sit in test mode the values never change, and when you spin them, the optics seems to work perfect..they don't jump around and they aren't jerky.
-Mark
 
Back
Top Bottom