Discs Of Tron Stuck In Test Mode

72Demon

Active member
Joined
Dec 2, 2008
Messages
442
Reaction score
82
Location
Kaneohe, Hawaii
I am hoping someone can help me figure out why my UDOT is stuck in test mode. It was working fine the last time I used it, and now when I power up, it goes straight into test mode, and can not exit it. You can do all the tests in test mode but it will not exit. I checked the test mode switch and it is not shorted and using continuity, it operates correctly. I checked the wires from the test switch to the board and there are no shorts. Reseated the connectors on the board, checked to see if it was showing a short between the pins, but nothing.

Any ideas?
 
does the test mode show if the test switch itself is "on" (don't know if the test mode shows the status of test modes on DoT)

if it shows that it's on most likely the IC chip that buffers the test switch is bad.
 
does the test mode show if the test switch itself is "on" (don't know if the test mode shows the status of test modes on DoT)

if it shows that it's on most likely the IC chip that buffers the test switch is bad.

In test mode, using the user input screen, it does not show anything when you switch the test mode switch. I am not sure if it would do that normally, I had thought it would take it out test mode if you tried that - if it was working correctly, of course.
 
most likely its the chip on the SSIO board that the test button connects to. I'll get out the schematics later this weekend and see which chip it is.

-brian
 
According to the schmetics its the 74ls244 at position F2 on the SSIO board (top board)
 
According to the schmetics its the 74ls244 at position F2 on the SSIO board (top board)

Thanks for the information Brian. I was hoping it would of been a socketed chip. I will have to dig out the soldering iron. Will let you know when I get a chance to do it.
 
OK, removed the chip, soldered in a socket. replaced with new 74ls244 at position F2 on the SSIO board and now I get "M error". Either in test or normal mode, that is what it boots to. I can not find anywhere what that means. Anyone know what M Error is?
 
What happens if you remove the ribbon cables from the SSIO board? Not sure what the m error signifies.. But if no one else chimes in and if I get time I will disassemble the discs of tron code to see what is causing that error.
 
If I remove the ribbon cables from the top board, I get a Bally/midway copyright, sound board type screen. If I leave it on, it boots to a test screen, then Discs of Tron, all upside down then it cycles back to the Bally/midway copyright sound board type screen and back again. Once I reconnect the ribbon cables it goes back to the "M Error" fault. Any ideas?
 
and there is no other text besides "M Error"? When you take the board off are there any missing text etc on the screen?

The reason I say this...is that screen shot I displayed... doesn't actually exist. (I had to create it, to see if that error looked the same of some letters missing from another error message)
The only 3 messages with the word "error" in the disassembly are
* ROM Error (from which the shot I got was taken)
* RAM Error
* Long Error about the IO board

The thing is both RAM and ROM match the pattern
"M Error" assuming the left two letters were missing.
Now that's entirely possible, if the video RAM that makes up those tiles are bad, it could cause a few columns of text to be blank. That also might explain why your game is resetting with the SSIO board off.. (assuming the RAM error is more widespread than just one chip (buffer issue?) but if that's the case I'd think without the SSIO board you'd still be missing those columns of text and probably have other video or resetting issues.

it also doesn't explain why you don't get those errors with the SSIO boards off!
Unless there's a short or broken wire to or on the SSIO board.

so it's a odd problem.

when you solered the new 74LS244 on did you detact any other ribbon cables besides the SSIO board? if so I'd double check to make sure they are all on and don't have a pin bent and not going in etc (or going above/below). If you didn't remove those I'd look again at the cable to see if you have a broken cable.. if not then I'd take another look at the SSIO board to see if maybe there's a break or a short where you soldered the 74LS244.

the symtoms are strange but the only thing I can think of that would cause those other letters to disapear would be a issue with the RAM or the address/data bus causing that part of the screen to be blank. perhaps if you take it apart just ensure all the socketed chips are also firmly inserted.
 
Last edited:
Thanks again for responding Brian. There is a blue square before "M Error". That is the only difference from your link. I did only remove the top ssio board so only those cables were removed. I double checked to make sure the cables were reconnected properly. I can try disconnecting the ssio board and see if there is missing text in the same location as the missing letters. Not sure if it will be in the same place since the picture inverts when I do that. Here is a picture of the error:
 

Attachments

  • IMG_0486.jpg
    IMG_0486.jpg
    130.5 KB · Views: 15
Last edited:
yes please do send a screen shot that would be helpful.
we can also get the screen to flip with the SSIO board off... I have to figure out what line to short on that. but will do that later this week if time permits hopefully the screen shot will help out.
 
also if you can take a short video of the game withthe SSIO board off
you mentioned it resets. let it go through at least one reset loop.
 
Here are some more pictures of the screen with the cables disconnected from the SSIO board. What was really crazy, when I first powered on again this time with the ribbon cables disconnected from the SSIO board, it looked like it was booting up correctly but with a inverted picture. Then it started cycling like the last time when the cables were disconnected. Once I reconnect the ribbon cables, it only gives the M Error screen.
 

Attachments

  • IMG_0489.jpg
    IMG_0489.jpg
    114.3 KB · Views: 8
  • IMG_0488.jpg
    IMG_0488.jpg
    22.5 KB · Views: 10
odd... my guess is RAM error... but if you had a ram error you should also have it with the SSIO board unattached. I'm at a loss without having more troubleshooting tools.

have you rebuilt your power supply in the last 10 years or so and replaced the 2 big caps?
when odd problems or unpredictable problems occur, never hurts to ensure the power is happy.

you don't have a fluke 9010 by any chance?

-brian

Here are some more pictures of the screen with the cables disconnected from the SSIO board. What was really crazy, when I first powered on again this time with the ribbon cables disconnected from the SSIO board, it looked like it was booting up correctly but with a inverted picture. Then it started cycling like the last time when the cables were disconnected. Once I reconnect the ribbon cables, it only gives the M Error screen.
 
I have the MCR Adapter with Switcher installed. Multimeter wise, I have a Fluke 113. Any ideas on what ram it would be?
 
For the fluke I meant the 9010 which lets you query memory to test it.

Offhand could not tell you which rams to try to replace but...
In regards to the ram I'm concerned that perhaps the memory circuitry either the address bus or data bus circuitry might be bad since you have both odd video issues and resetting.
 
Back
Top Bottom