(Topic ID: 57770)

Bally EB strange behavior from MPU, Display & Lamp problems SOLVED

By mg81

10 years ago



Topic Stats

  • 10 posts
  • 3 Pinsiders participating
  • Latest reply 7 years ago by mg81
  • Topic is favorited by 2 Pinsiders

You

Linked Games

You're currently viewing posts by Pinsider mg81.
Click here to go back to viewing the entire thread.

#1 10 years ago

My Eight Ball is doing some strange behavior that I can't find an answer for. The game has worked well for a long time. It does have the standard corrosion damage in the battery area, but nothing that has affected performance after I cleaned things up right after I purchased it. It has worked well for over a year.

I did just remove the MPU and move it around to another pin for testing out the other pin (I needed a known good MPU). Now I am getting weird behavior, perhaps unrelated to the move but I figure I should mention that I did it.

When the pin is cold and I start it the game will fully boot, all 7 flashes on the MPU. But the displays will all come up weird, numbers in the wrong spots and many of the controlled lamps on the playfield will be lighted that should not be.

If I start to play a game everything will work (coils, kick back lighting, etc), but many of the controlled lamps that should not be light will be lighted and the displays will not score correctly. Like Player ones 1,000's position will also show up in the player 2 far right scoring position simultaneously. Other problems as well, the displays will be flickering, all displays. No nice steady, numbers.

If the game is on for a while and I try to restart it I will only get two flashes on the MPU. That means either the U8 chip, U8 socket or U19 is bad according to Clay's. I have swapped in a known good U8 chip and the MPU will still not boot (only two flashes) until it sits around for a while to "cool" off.

I hate to start throwing parts at the pin without a plan. What will cause both the controlled lamps and displays to totally wrong? I can put in the new U19 and U8 socket, but would either of those cause this problem? Could I have messed up a trace when moving the board that would cause this to happen?

Thanks for the help.

#3 10 years ago

I just looked at my old notes from when I purchased the pin. It appears that I already did replace the U8 socket. I would have cleaned the area thoroughly after striping the parts and before putting new ones on with vinegar, distilled H20 and alcohol.

-R11 replaced
-Misc. parts below U8 socket replaced
-U8 socket replaced (this finally gave me my 3rd blink)
-New U8 & U11 chips
-New capacitor added to replace battery
-J4 pins 18 &19 to the main ground on MPU board (Recommended in Clay’s manual)

#6 10 years ago

Thank you for the ideas. I will trace everything out from U8 and and check for J1 connector issues.

The game had been working very well for over a year since my initial battery damage repair. I am pretty sure the problem relates to me moving the board around and probably damaging a trace or connector, since the problems happened right after my moving of the board.

I was just hoping that my symptoms pointed to one chip/area in general, it seemed odd that both the controlled lamps and display would be "working" but giving very incorrect behavior.

I will take it as a hint the since the board fails to give 3 flashes after heating up that it is in the U8 area and I will focus on those traces first.

#8 10 years ago

Solved. As most of you kept pointing me towards the U8 chip and that was the issue. Specifically the socket.

I had installed a new one about a year ago but the #1 pin of that socket showed ~50 ohms of resistance when I tested it with a DMM. So I sucked off the old solder and reflowed that pin and everything works perfectly now.

I am guessing that I had a marginal solder joint to begin with and the moving of the board broke that solder joint.

Apparently the U8 can pass the MPU self-test with that much resistance, at least some of the time.

Clay's actually specifically lists the U8 chip causing display issues just like mine in a game he was working one, the difference being that he was able to fix the problem by replacing the U8 chip. He also mentioned that the MPU he had still passed the MPU self test with the "bad" U8 chip, just as mine would. So, I guess the lesson is the MPU self-test will not always catch a bad U8 chip/socket.

Thanks again everyone for the help

2 years later
#10 7 years ago

These damn U8 (5101, RAM) chips go bad more than any other chip I have ever dealt with. This pin was giving me weird display issues and controlled GI issues AGAIN. I swapped out the U8 chip with a "new" chip (I don't think they have made a new 5101 chip in decades). It still did not work.

I wasted a bunch of time messing with other parts and finally put in another "new" 5101 chip in the U8 socket when I had run out of other ideas and the pin worked perfectly again.

Lesson learned, try several 5101 chips if the problem points to that chip.

Promoted items from the Pinside Marketplace
$ 199.95
$ 10.00
Lighting
Yoppsicle
Lighting
$ 29.99
Cabinet - Shooter Rods
Pinball Shark
Shooter rods

You're currently viewing posts by Pinsider mg81.
Click here to go back to viewing the entire thread.

Reply

Wanna join the discussion? Please sign in to reply to this topic.

Hey there! Welcome to Pinside!

Donate to Pinside

Great to see you're enjoying Pinside! Did you know Pinside is able to run without any 3rd-party banners or ads, thanks to the support from our visitors? Please consider a donation to Pinside and get anext to your username to show for it! Or better yet, subscribe to Pinside+!


This page was printed from https://pinside.com/pinball/forum/topic/bally-eb-strange-behavior-from-mpu-ideas-needed?tu=mg81 and we tried optimising it for printing. Some page elements may have been deliberately hidden.

Scan the QR code on the left to jump to the URL this document was printed from.