Gottlieb Solved Domino (Gottlieb, 1968) tune-up

[Jilpoked]

Hello and pleasant greetings, I have a 1967 Gottlieb Domino pinball game. It is a single player and features an active play surface with four pop-bumpers a roto-unit, two hole-kickers and kicking rubbers, a pair of flippers and all of the associated scoring roll-overs and contacts. The game is in very good condition aside from some wear to the playfield art at the flipper area. It had a smoked flipper solenoid when purchased, in '98, which I was able to replace. It was fully functioning for many years but has recently developed a couple of issues.

A couple of weeks ago I decide to give the old girl a little well deserved and overdue TLC. I pulled out the schematic, opened up the machine and went to work. I removed each relay from its mount, inspected their wiring terminals and the condition of their contact points. I silently rejoiced when, while inspecting the 'R' relay, one of the wires soldered switch connection parted from its lug. I had to disassemble the switch stack in order to reattach the wire but, alas, once repaired it did not fix the problem. I inspected all the stepper units, score wheels and the roto unit.

During inspection, I noted the many jumper pins and wires populating most of the relay switch stacks. I can not figure out how the wiring schematic is representing this information. I soon realized that locating the problem was probably beyond my abilities.

In the center of the playfield sits a roto target with paddles of differing dot configurations. Painted on the front/center of the playfield is a circle of 15 dominoes, each with a lighted half that is lit through a translucent plug by a bulb below the play surface. When these are lit and a matching roto target is struck points are scored. When working correctly, after a restart, the first domino left of center, with 5 dots, would light and as play progressed the next in line domino would light, in turn, around the circle until the last domino, with 6 dots, would light with coinciding bonus scoring.

THE PROBLEM; Now, when the game is started, the last circle domino, with 6 dots, is brightly lit but without bonus scoring feature. It stays brightly lit through the entire game. The domino circle lights are powered through a stepper unit. When I open the machine and manually rotate the stepper I see the correct circle dominos are lighting but so faintly that they are not visible above the playfield. As play progresses and the stepper unit advances to the last position bonus features are added.

Another problem/symptom is the center target. There is a light associated with the center target which reads '100 pts. when lit'. At times while the light is on the target will only award 10 points. When it is in the lit/ten point mode and the target is depressed and momentarily held by hand a rapid clicking comes from the '0 - 9' stepper unit in the upper box.

I read through the posts in this repair forum that I hoped might shed some light on my problem, to no avail. I have pics of the complete schematic. I hope someone can help me straighten out this old girls clothes and smudged lipstick.

 

[pinballdaveh]

the 6 domino light is the 14th or last step for the domino advance unit. if the light stays on after reset , the domino advance unit is not resetting properly. the domino advance unit subtract or reset coil fires at the same time as the ball count unit subtract coil and playmeter without any additional switches. mech binding or dried lube might be the problem. has the domino advance unit wiper disc been removed and rivet board cleaned? the domino advance unit along with 3 resistors pull in the B,C,and E relays that control the score for its selected shots. clean and adjust switches on these 3 relays , and check if they pull in correctly when unit advances.

 

[Jilpoked]

Dear Pinballdaveh, Thank you for your detailed reply.
Yes, I removed the wiper from the advance stepper, cleaned and lightly buffed the rivet heads with a scotch pad, followed with a very light coating, to the rivet heads only, of a silicone based lubricant. The shoes or brushes were given similar attention.
I will reexamine the advance stepper and do the other things you advise. Pinballdaveh, you are the man!
Thank you again for your time and effort. Best regards, Jilpoked

 

[Jilpoked]

Dear Pinballdaveh, I went thru the advance stepper and I feel confident that it is functioning properly. I checked the B,C and E relays, their contact points look good adjustment wise and there is good wiping motion when contact is made. The relays seem to be cycling on and off, but I'm not really sure when they should be on and off.
I'm still puzzled by the 6 dot domino being lit thru the whole game. It should be the last one in the circle to light, and then along with the bonus features. I unsoldered the two wires from the 6 dot domino light, showing continuity from one wire to the last contact on the advance stepper plate and the other wire with continuity thru the Motor 1C switch to the bonus feature lights. Are the bonus feature lights then powered from the last contact on the stepper plate? The schematic shows two paths from the last stepper position or 6 dot light, one from the advance unit and the other thru a NC switch and Motor 1C.
I think that if I can find why the 6 dot domino is being powered from the start that it may lead to the ultimate fix. I hope this make sense. Best regards, Jilpoked

 

[pinballdaveh]

along with the 6 dot domino , does the special lights work as they should on the last advance step? you can back track the path of the 6 dot domino light wire to the jones plug , check that wires match from male to female. check for solder splash shorts or touching connections. check wire back to score motor switch for shorted connections. un-solder wire from advance unit to eliminate unit as the problem.

 

[Coil_Smoke]

That Motor 1c contact should energize the special features lamps that are active when 6 domino is lit. It should not have power flowing "backwards" through it and lighting the 6 domino. it looks like the only proper way to light the 6 domino is through #14 connection at domino stepper unit{Is power on at #14 if the wire to #6 domino is removed?}. Are the 4 special lamps lit along with #6 domino? At a glance the domino stepper unit lighting circuit looks fairly simple with it energized as long as playfield lamps are powered. How else can power be getting to your 6 dot domino? Sometimes I see a wire in the bundle at a relay disconnected and the game is working just fine. Could your initial "repair" be the source of the errant power lighting your 6 spot domino?

 

[Coil_Smoke]

S H O C K I N G . . . !

Wow, this machine's schemo shows 120 VAC line voltage, that resets the relay bank, flowing through score motor and relay contacts ! Truly Shocking

 

[pinballdaveh]

many large banks that are not split reset with 2 coils will be a single 120vac coil , usually fused. on gottlieb pins plastic insulated wire was used for 120v circuits. yes 120vac is found on the score motor switch. so caution should be used when touching or cleaning switches when machine is on. whats more shocking is that older gottliebs the metal replay button was insulated from a 120v switch with fish paper.

 

[Jilpoked]

Dear Pinballdaveh and Coil Smoke,
Thank you guys for your help. I still have some work to do in order to answer all of the questions in your posts. I definitely need help with this great old game and I do appreciate your efforts.
First, thanks for the heads-up on the 120VAC! Made me think about a friend of mine who loves tinkering with electrical household components. He's had to give it up for a while, to let his eyebrows grow back! Just kidding but I do know that 120VAC can be deadly.
Coil Smoke your question about my previous repair is a good one, but I saw the wire come loose in my hand. I had removed the relay from its mounting and was turning it to get a good view of the contacts when it popped off. There was a perfect imprint of the contact blade including a little cylinder of solder that matched the hole of the blade end. Kinda looked like a lego,
Pinballdaveh, yes the 'special when lit' lights do come on when the stepper reaches the 14th or last step. I followed the wire from 6 dot light thru the score motor 1c switch to the jones plug, with continuity to and thru the jones plug. No evidence of solder splash or touching connections or any chaffing. I un-soldered the wire from the 6 dot light that runs to the steppers 14th contact. When I powered the game the 6 dot light was burning brightly from restart and would only flash off when the score motor was rotating between its resting positions. This would indicate that the 6 dot light is receiving its power from the score motor.
Coil Smoke, your comment about the motor 1c energizing the special features lamps that are 'active', made me think... is something allowing or making 'active' the 1c circuit from the score motor to the 6 dot lamp? With the wire from the 14th contact of the stepper removed from the 6 dot light, I restarted the game and, as stated above, the 6 dot lamp lighted immediately. I then manually ran the score up while observing the advance wiper, when it reached the 14th contact the 'special when lit' lamps did not light until I touched the removed wire to the 6 dot lamp lug which was receiving power from the score motor 1c switch.
This Advance Unit stepper, made in pre-printed circuit board days, is the most complex device in this machine. I imagine their manufacture was given to the top technicians in the shop. The wiper rotates about 180 degrees before reaching the 14th contact and end of its throw. The wiper is double ended, or has shoe/brushes on either end which are slightly different in configuration. The riveted contact plate is supplied with different voltages. The side of the plate that powers the circle domino lights is furnishing about 2 volts, while the other side powers the B, C and D relays at 30 volts. It may provide power to other areas, I don't know.
As I stated in an earlier post, when I open the machine, power it up and restart, I can manually turn the stepper wiper and observe the circle domino lights from below the playfield. They glow so dimly that you can not see any illumination thru the translucent playfield plugs.
Pinballdaveh you described three resistors in the 'advance unit' circuitry, are these resistors used to provide the different voltages found on the contact disc? If so, is less than 2 volts sufficient to power a playfield light? Can these resistors fail and cause intended voltages to drop?
Pinballdaveh and Coil Smoke, thank you again for the time and effort. Best regards, Jilpoked

 

[Coil_Smoke]

It sounds like the power lighting your 6 spot domino must be coming from your score motor, Uhg. Some careful study of those contacts may reveal something sticking, broken, out of adjustment or touching something it should not. Playfield feature lamps are looking to get 6 volts(6.8 ). I am not familiar with the fore mentioned resistors and wonder why only 2 volts is reading at your stepper ? Even that 30 volts seems odd. I would think it should be closer to 24 V. I will note the two transformer secondaries might add up to 30 V if wired in phase with each other. Maybe the game is on low volt primary tap?

P>S>Well, your schemo does not show a low volt primary tap. But your secondaries are 'interesting' with a possible 30 Vac tap above the traditional 24Vac lug. And two taps for lights- a 6 Vac plus a 5 Vac for other lights. The pagenated schematic makes it hard to tell exactly which circuits get what volts.

 

[Jilpoked]

Dear Coil Smoke,
Thank you again for your efforts. Yeah, I agree the score motor must be providing the power to the 6 dot light and I know that it should not until enough points are scored to allow bonus score features, maybe. I have had my nose down there next to that score motor and a hot drop light many times, I have unpinned it and turned it up to see the bottom view and I can't find anything out of place.
Trying to trace or isolate circuits, on this pinball, with a meter is tough. The way so many of them are being backfed from somewhere not readily known. With the way the switch stacks are criss-crossed with jumpers is pretty intimidating to me! I really didn't want to open every bundle and physically follow each wire but it might be the only way to understand what is going on. The techs that made up the looms did such a nice clean looking job with that waxed twine, I can imagine how clunky it will look after replacement with a bunch of plastic tie-wraps.
I ordered the pinball book by Kamoroff. I hope that it lives up to its billing. It should be here any day now. I want to thank you again for the help. I will get to the bottom of the problem and when I do I will share it with everyone. If you have any moments of inspiration, please share them as well, I'l be watching the page. Best regards,Jilpoked

 

[pinballdaveh]

im not sure what those resistors are used for , but i will launch this idea and see if its believeable. the resistors are used in a coil preheat that puts some voltage to the coil but not enough to pull it in. when the advance unit wiper gets to one of those resistor positions. the wiper completes a zero ohm circuit and takes the resistor out of the circuit. by adding those resistors a smaller arc may happen on the disc that drives those relays.

 

[Jilpoked]

Hello and pleasant greetings to all,

Wow! Sometimes just being lucky is enough. I have been concerned about the low voltages my meter is showing for the circle domino lights. I felt that the three resistors used in the 'advance' stepper were perhaps failing in whole or part. I was only reading about 1.75 volts from the lighting side of the 'advance stepper. Coil Smoke offered that the schematic is showing between 5 and 6 volts. and that generally, a lighting section would require 6 volts.

Using a meter to troubleshoot this problem has often left me more confused than enlightened especially when attempting to determine continuity! I think part of the reason may be the way power is brought into the machine. The power cord plug has just the two flat blades with no third or ground(?) wire. This kind of circuitry is hard for me to understand, but it eventually led me to stumble onto what was causing this problem!

I was thinking about the low voltages my meter was showing and decided to drag out an older meter that I have and compare the readings. I turned on the pinball machine and restarted a new game. I ran the score up high enough to make sure the 'advance' stepper was active. As per the problem, the 6 dot domino lighted immediately, well before it should be. As I said, I wanted to check the voltage of the lighting half of the stepper. There is a bare wire stapled to the underside of the playfield that is used as a grounding(?) wire for this circle of domino lights. Each light socket is soldered to this bare wire and then has an insulated wire, or two, soldered to the positive lug of the socket. The bare stapled wire is flat against the wood and stretched tight so I had to manipulate the wire in order to get the alligator clip to stay put. As I did this the 6 dot light flashed off, and one of the other circle domino lights flashed on very brightly! It took a few moments for me to realize that this was a good thing. I then measured the voltage at the stepper and it was showing over 6 volts. I examined the solder connection of the socket nearest to the alligator clip and discovered that it had broken loose. I repaired the connection and this problem is history! I did the obligatory victory dance, my shoulder is a little sore this AM, as I may have patted myself on the back with a little too much vigor.

I guess the lesson here is; Wood can swell and shrink over time, these stapled wires are stretched tight when they're assembled and soldered. These solder points may not be strong enough to resist this extra stretch, they may fail. Check these common 'grounding' wires at all soldered connections, especially at any corners.

I want to say thanks again to Pinballdaveh and Coil Smoke, you guys totally rock! I was wondering, though, if one of you might explain to me, how does providing a better ground for the 6 dot light, that was receiving its power from the 1C circuit of the score motor, make that light go out?

I have attached a couple of pics. The close-up shows the bare stapled wire where I attached the alligator clip, the upper light socket is where the solder connection failed. The other pic I loaded inadvertently and couldn't figure how to remove. Best regards, Jilpoked

 

[Coil_Smoke]

how does providing a better ground for the 6 dot light, that was receiving its power from the 1C circuit of the score motor, make that light go out?

I have seen odd things happen in complex series/parallel circuits. They can form unintended circuit paths when things go wrong. Congratulations, it is great news your machine is behaving .

 

[pinballdaveh]

thank you for the pics. is that the domino advance unit next to the roto unit. pics of those may have been helpful.