Help with a sketchy Tron spinner?

jehuie

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So I got this Tron and it was working well except that the spinner was a little bit sketchy. It would jump sometimes, making it hard to aim. Then all the sudden it was working great so I kind of forgot about the problem. Well today I took the control panel off for some light-bulb maintenance and when I put it together, the spinner was kind of jumpy again.

So I took the spinner apart and investigated and found 3 things I thought were likely problematic:

1) A pin on the main connector was pushed out some, possibly making a bad connection. Pushed it back into it's proper spot.

2) Two of the plastic clips that hold the optic board in place were broken, allowing the board to move around. Strapped it down tight with a long zip-tie as a temp fix. Seems very stable now.

3) One of the capacitors on the board was completely disconnected on one end. Remove the capacitor and put a new one in its place.

Cleaned the optics with alcohol and slapped it all together and it worked beautifully for exactly one game. But then it suddenly got way worse than it ever had. It only operates in a very small range. I put it in test mode and the numbers are suspicious to me: it goes from 64 to 127 which is awfully close to 2^6th power and 2^7th power.

So what do you think? Spinner issue? Or PCB issue?
 
In test mode the numbers should go up and down smoothly and shouldnt skip. If you see it jumping around you have issues with your spinner pcb. First thing to check is make sure your power is good to the board. Low voltage will cause weird things to happen. The optics do get dirty and can cause problems that come and go. If an optic was bad it usually wont be intermittent. The 74LS491 (counter) on these tend to go bad alot. Usually its either the optics or 491 assuming the power is ok.
Here is a link that may interest you...
https://www.twistywristarcade.com/search?orderby=position&orderway=desc&search_query=tron
 
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Thanks guys. And thanks for the links. I'm tempted to buy the whole replacement unit but I'd rather not just throw that much money at the problem until I'm sure it's the spinner hardware that's the problem. The numbers to move smoothly within the range that they are working. But when it gets to the 127 it just jumps immediately to 64 (and vice versa). Which sounds like a logic problem to me. So it sounds like you guys are saying it's most likely in the optics board somewhere. Hmmmm....
 
Im saying check your voltage going to the optic board first. I have seen a few of these that has issues resolved simply by adjusting the voltage up a hair.
But yeah bad or dirty optics, bad ls491 will both have similar symptoms.
Btw, if you buy the replacement pcb it does come with new mounting hardware.
 
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Thanks again. I totally missed the part where you said to check to be sure that power is good to the board. Time to dig out the schematics to see where to measure!
 
Thanks again. I totally missed the part where you said to check to be sure that power is good to the board. Time to dig out the schematics to see where to measure!

Yeah, I dont remember off the top of my head. I will see if I can find my manual...
 
Pin 2 is ground, Pin 1 is +12 and pin 13 is +5.

Thanks for saving me the time looking it up! I thought that had fixed it. My voltage at the board was around 4.7 when I checked it. I adjusted VR102 up as high as it would go and got it up to around 4.9 and it was working beautifully at first. But then about 3 levels into the game it started doing the same thing again. Is 4.9 still borderline or should it operate properly at that voltage you think?
 
4.9 is probably ok as long as its not dropping down when under a load. Make sure your not getting the +5 too high on the main board by cranking that pot all the way up.
 
4.9 is probably ok as long as its not dropping down when under a load. Make sure your not getting the +5 too high on the main board by cranking that pot all the way up.

Yeah, I measured it at the board there to be sure it wasn't going to screw something up there. So it could be the optics or that main chip. Should I just replace those since they are inexpensive? Or replace the whole board just to be safe?
 
Well, I removed and replaced the solder on the header pins and touched up the solder on the optics and it's working....so far....

Thanks!
 
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