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(Topic ID: 275656)

FMBC Game starts and lasts!

By Iwasthebruce

3 months ago

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  • 6 posts
  • 2 Pinsiders participating
  • Latest reply 3 months ago by Iwasthebruce
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4MBC Game Over relay (resized).jpg

#1 3 months ago

Hi all! This is my second EM, but the first one that needs service in the "logic" department (the other one was 100% mechanically, just needs a ton of cosmetic work).

So, here we have a 1971 Bally Four Million BC (SN 3410) that I recently bought from an arcade enthusiast, who admitted pinball was not his forte. He had the game for a year after purchasing it from a woman who had the game in her family for as long as she could remember. Sold it to me as is. Kicks out 2 balls at game start, game never ends. I figured out the 2 ball kickout already (Tar Pit thought it had a ball in it still, easy!) However, the infinite game makes it not-so challenging...

During my inital inspection, I have not found any hack jobs and all components appear to be intact and present. A couple coils have burnt paper, although all still function except for the "close flippers" solenoid. Poor thing looks like a spent firework, already ordered a replacement and verified the mechanism can be manually operated smoothly with no issue. I also intend to replace the other coils once they arrive.

Now, on to the real meat and potatoes:
Plug it in, flip the switch, and press the left flipper button and she comes to life in a "GAME OVER" state.

As soon as either the 1st or 3rd coin chute is triggered, a game starts (without pressing credit/start button). The results are the same if I manually fire the coin coils. If I neglect the coin chute, I can also manually press the credit coil to get up to all 4 players active. Issue is, I don't believe the game should start on coin chute, but on credit/start button press, correct? I've metered for continuity at the credit switch behind the coin door, the switch is not shorted and appears to function correctly, despite not activating anything.

Once the credit is activated, the score reels reset, player 1 is illuminated, and a ball is kicked out. Plunge the ball and score some points, except the Ball Count does not illuminate. Ball Step Up Unit (correct terminology?) Is functioning, unit moves to all positions without manual interference, however, Ball Count is not reflected by the lights in the back box.

After a ball is drained (on multiplayer) the next player is lit and a ball is kicked out. However, the game is infinite, never reaching a "GAME OVER" state.

I'm starting to suspect either contacts on the ball count step up unit (although the leafs appear to be making physical contact) or an issue further down the line.

Tl;dr: Game starts on coin chute and does not ever end...infinite drains!

Any advice is appreciated, thank you in advance!

#2 3 months ago

Ok, I've resolved the coin chute issue by working around it and setting the game to free play. I set to free play by shorting the credit wheel unit switch for "0" and now the credit/start button functions correctly.

Something seems to be intermittent for the ball count...I had a light for Ball 1 for a split second whilst probing about.

So close to being able to cycle a game correctly!

Any suggestions are still more than welcome, thanks!

#3 3 months ago

The Game Over Trip relay should fire when the Ball Count step unit reaches the ball 3 or ball 5 position, depending how you have it set:
4MBC Game Over relay (resized).jpg
Given that you're not getting Ball in Play lights either it could be that the connection to the 30/Yellow common wire (at the top) is broken somehow since the lights would require on that too.


#4 3 months ago
Quoted from MarkG:

The Game Over Trip relay should fire when the Ball Count step unit reaches the ball 3 or ball 5 position, depending how you have it set:
[quoted image]
Given that you're not getting Ball in Play lights either it could be that the connection to the 30/Yellow common wire (at the top) is broken somehow since the lights would require on that too.

Thank you for the suggestion! I just metered the yellow common between the ball count unit and the game over interlock and I have continuity.

I've also inspected the red-white and red-black common at the lights and they have continuity between themselves and the jones plug in the back box. Also metered for voltage at the socket and it is not energized (while step unit is on ball 1 position).

#5 3 months ago

Sorry, I don't follow any of that. Can you elaborate? Which two points for example were used in each measurement?

And beware that continuity only tells you that there is a conducting path between your probes. It could be a path through a coil, through the transformer or anywhere else through the game. It's not necessarily through the path you expect.

I would suggest unplugging the game and clipping one meter probe to the yellow/common wire and the other probe to the solder lug on the Game Over trip relay with the green-red wire. Block the switch on the Lock relay with a piece of paper and make note of the resistance reading. Then manually advance the Ball Count Unit to the 6th position. You should see the resistance drop to an ohm or less indicating that there is a path from yellow to the relay coil through the Ball Count unit 6th position. For extra credit move the probe and check the yellow/common wire in several places because the problem may be in the yellow/common connection but not right at the Ball Count unit.

#6 3 months ago

Thank you for the knowledge, I am new to troubleshooting this type of machine!

I had tested between the yellow wire, at the solder point, on the ball count and the solder connection at the switch on the game over relay interlock. Good to know to check for resistance as well.

I went through and cleaned some of the contacts and the jones plugs and have the game running now, amazing how destructive a bit of grime can be!

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