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Gottlieb 1972 Gottlieb Grand Slam Reel Reset and 1 weak pop bumper

teamhex

I PwN nOoBs
I signed up on here ages ago when I was in my late teens. I've had this machine for quite awhile now and I decided I should start trying to fix some of the issues.

I recently replaced all the rubbers, bulbs, and plunger springs so it plays a lot better.

It plays, but It would be nice to have an accurate score for each game played. Instead it just resets to 0 and counts up if you get over 99,999.

On a rare occasion the score/runs will reset when you "insert" a coin, but I found a way to reset the score reels by tapping this relay then putting a coin in.
Could someone tell me where to look to make the score reset reliable? I'm guessing this is a dirty contact type situation since it does occasionally work....we're talking...once every 40 games or so.

Here's a video of me showing the relay and the process I use to reset the reels. Also here's some pictures of that relay.


Also my left pop bumper doesn't seem to launch the ball at all. It does pop when hit, but doesn't kick the ball back like the right one does. I assume this is an adjustment issue, but I could be wrong.
 

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Ike Savage

Froggy like robot
Staff member
Site Supporters
Hmm. The schematics don't seem easy to find anymore, I guess because Gottlieb pulled most of their resources online.

There's a guy who stops by regularly who can probably sort this out, but meanwhile you might want to start looking at PinRepair.com.
 

teamhex

I PwN nOoBs
I think I have the originals in a tube and some reproduction ones in a manila envelope. The issue is reading them. Funny enough I'm a computer technician, but I don't go down to the circuit level of things. If a part is bad we just replace it.
 

Ike Savage

Froggy like robot
Staff member
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I think I have the originals in a tube and some reproduction ones in a manila envelope. The issue is reading them. Funny enough I'm a computer technician, but I don't go down to the circuit level of things. If a part is bad we just replace it.
Hah, yeah... I also used to be a PC tech guy (long time ago, now) and never really learned the circuit side past the beginner level. For me, the main use of a schematic in these EM's is to trace back to some likely relays, clean them up and cross my fingers. I used to use white eraser pencils and occasionally other stuff to clean the leaf switches back when I had some EM's. Hopefully you've got some supplies like that around there.

If Dave sees this I'm sure he'll have some ideas. But that PinRepair site will probably give you some good ideas about where the troubles might lie so at least you can get started.
 

pinballdaveh

Pinball Technician
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Hah, yeah... I also used to be a PC tech guy (long time ago, now) and never really learned the circuit side past the beginner level. For me, the main use of a schematic in these EM's is to trace back to some likely relays, clean them up and cross my fingers. I used to use white eraser pencils and occasionally other stuff to clean the leaf switches back when I had some EM's. Hopefully you've got some supplies like that around there.

If Dave sees this I'm sure he'll have some ideas. But that PinRepair site will probably give you some good ideas about where the troubles might lie so at least you can get started.
All gottlieb EM machines use relays to control pop bumper operation.
Sometimes the pop bumper cap color is what the pop bumper relay will be called.
Sometimes a pop bumper relay will operate 2 pop bumpers at the same time.
Normally open switches with larger points are used to drive the pop bumper coils on the pop bumper relay.
Taking apart the pop bumper to clean the coil sleeve and plunger is helpful.
The video shows you tricking the machine into thinking that the reset sequence has been completed by flicking that coil plate.
It looks like there’s issues with the reset circuits that needs fixing.
Familiarize yourself with gottlieb reset sequence thru online videos.
 

teamhex

I PwN nOoBs
All gottlieb EM machines use relays to control pop bumper operation.
Sometimes the pop bumper cap color is what the pop bumper relay will be called.
Sometimes a pop bumper relay will operate 2 pop bumpers at the same time.
Normally open switches with larger points are used to drive the pop bumper coils on the pop bumper relay.
Taking apart the pop bumper to clean the coil sleeve and plunger is helpful.
The video shows you tricking the machine into thinking that the reset sequence has been completed by flicking that coil plate.
It looks like there’s issues with the reset circuits that needs fixing.
Familiarize yourself with gottlieb reset sequence thru online videos.
Excellent. I'll bust out the paperwork here and see if I can figure out that restart sequence.
I assume the scores are supposed to reset at the beginning of the game based on past experience of it working.

I'm just curious why the reset complete relay...resets the reels. Seems odd to me. So I know the reels work for sure since they do reset when I do that. I guess I should be looking at what ever sends a signal to that reset complete relay coil and start there.

The pop bumpers seem to work, but only the right one launches the ball with enough force to actually send it away from the bumper. The left one just pops, but doesn't launch it. I'll start by taking it apart. I did read that if it activates, but doesn't launch the ball the issue is most likely a switch that needs to be adjusted. Something about it being activated with a light touch. Maybe it's travel is too far so it doesn't activate in time? No idea, but I'll with that I guess.
 
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teamhex

I PwN nOoBs
Upon inspection I figured out why the left pop bumper isn't launching the ball...though I'm not sure what I can do to fix it other than buying a new rod assembly with the nuts.

The rods aren't connected to the plate on the coil. The pop bumper on the right has threaded ends with some small nuts on it.
I'm starting to think someone put on a rod assembly from another machine or something. I don't even see threads on these.

If anyone knows a site that sells them and knows what part it is. Please link me. I'm going to take both apart and polish up both of them before putting them back together.
 

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pinballdaveh

Pinball Technician
Staff member
Site Supporters
Upon inspection I figured out why the left pop bumper isn't launching the ball...though I'm not sure what I can do to fix it other than buying a new rod assembly with the nuts.

The rods aren't connected to the plate on the coil. The pop bumper on the right has threaded ends with some small nuts on it.
I'm starting to think someone put on a rod assembly from another machine or something. I don't even see threads on these.

If anyone knows a site that sells them and knows what part it is. Please link me. I'm going to take both apart and polish up both of them before putting them back together.
Pinball resource for gottlieb.
Marco specialties has a good online order site.
I thought someone posted about all the parts sites awhile ago.
 

teamhex

I PwN nOoBs
Pinball resource for gottlieb.
Marco specialties has a good online order site.
I thought someone posted about all the parts sites awhile ago.
I'm new to this forum so to speak. I signed up a long time ago, but haven't had time to browse.


Alright so I talked to their support and mine doesn't use that longer style one. Got the new parts ordered. Guy was super helpful and recommended some other parts that should be replaced when you rebuild these. All set on that.

Thanks for all the help gents.
 
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