(Topic ID: 249244)

Gottlieb Pro Football (1973) - AB relay not activating on game start


By egg_sanwich

11 days ago



Topic Stats

  • 5 posts
  • 3 Pinsiders participating
  • Latest reply 10 days ago by egg_sanwich
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#1 11 days ago

Hi all,

I've had this Pro Football in my possession for some time, it came out of someone's crusty old garage on the island here. It's always had issues, but I've worked through most of them except this one that I just can't resolve.

Description:
When starting a new game, the AB relay does not activate to reset the score reels.

From the startup sequence:
The following sequence takes place thru the closed switches on "S" relay:
a. The motor starts running
b. The total play meter and AB relay coil are actuated by switches on motor 3C and motor 1A
c. The reset "Ball Count" unit coil is energized returning the unit to zero.
d. The advance unit ("I" relay) is pulsed by motor 1A to its zero position
etc.

My thoughts:
- The total play meter IS incrementing, and following the schematic, both the AB relay and total play meter go through the same set of switches (1A > 3C > S). I've also checked and adjusted all of those, so I don't think they are the culprit

- I suspected bad coils, so I replaced both the AB and AB Reset coils with the matching NOS coils ordered from Johns Jukes. This had no effect

- This isn't a 100% of the time issue. Maybe 1-in-10 or 1-in-20 times the AB DOES activate and the game begins as it should

- Unrelated (but possibly related), manually activating the relay resets the scores properly, but the AB Reset Relay fails to activate as well and must be manually triggered.

I've attached the relevant section of schematic and instructions, plus a picture of the AB coils (AB Reset is on the left, AB is on the right).

Any insights or ideas are welcomed, thanks in advance!
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#2 11 days ago
Quoted from egg_sanwich:

When starting a new game, the AB relay does not activate to reset the score reels.

Quoted from egg_sanwich:

The total play meter IS incrementing, and following the schematic, both the AB relay and total play meter go through the same set of switches (1A > 3C > S). I've also checked and adjusted all of those, so I don't think they are the culprit

Good observation. I suspect your AB interlock relay is either mechanically or magnetically bound. If you need more proof that the circuit is working as it should you could use a bulb tester (described elsewhere in the forum).

You could try cleaning, polishing or even waxing the two armature plates to minimize the friction between them. You could also try to adjust the relative positions of the two relays so that they just barely interlock. Be sure to check the switches though to make sure that they all open and close as the relay toggles between the two positions.

It's also possible though unlikely that the springs were replaced with incorrect springs at some point and are too tight.

There are probably some other topics about interlock relays in this forum that might help too.

/Mark

#3 11 days ago

Another useful test would be to temporarily connect the Orange & Blue wires on the AB relay to the same color wire on the Total Play meter or the S relay with an Alligator Clip jumper wire.

#4 10 days ago
Quoted from MarkG:

Good observation. I suspect your AB interlock relay is either mechanically or magnetically bound. If you need more proof that the circuit is working as it should you could use a bulb tester (described elsewhere in the forum).
You could try cleaning, polishing or even waxing the two armature plates to minimize the friction between them. You could also try to adjust the relative positions of the two relays so that they just barely interlock. Be sure to check the switches though to make sure that they all open and close as the relay toggles between the two positions.
It's also possible though unlikely that the springs were replaced with incorrect springs at some point and are too tight.
There are probably some other topics about interlock relays in this forum that might help too.
/Mark

Great suggestions here, thanks Mark. I've inspected/cleaned the switches on these relays so I don't think that's the issue, however I'll look into reducing the friction between the two plates. It does seem like they are trying to pull, albeit unsuccessfully. Fodder for deeper investigation for sure.

Quoted from HowardR:

Another useful test would be to temporarily connect the Orange & Blue wires on the AB relay to the same color wire on the Total Play meter or the S relay with an Alligator Clip jumper wire.

Thanks Howard, I'll give this a go as well to see if power's getting through.

Cheers,
Mike

#5 10 days ago

I followed howardr's advice and confirmed the circuit was working.

Looks like markg was on the money this time though! After cleaning/polishing/waxing the armature plates with no success, I was able to adjust the position of the AB coil and arm to reduce the friction between the two plates. Sure enough, the AB and AB Reset were working like a charm after that.

Since I had repositioned them, the switches needed a bit of adjustment to get back on track. After that though, everything is now playing as it should

Thanks again guys!

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