(Topic ID: 278287)

The scan bonus unit of CANADA DRY / TARGET ALPHA / SOLAR CITY

By kangourou

1 year ago

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  • 11 posts
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  • Latest reply 1 year ago by drumsetz
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#1 1 year ago

The scan bonus unit of CANADA DRY / TARGET ALPHA / SOLAR CITY

Sorry for the translation by Google...

This article is the compilation of several posts from Flipjuke, Retroflip and Pinside, as well as from my personal experience.

I would like to thank Jean-Luc Therville, a French collector, who, a few years ago, gave me a better understanding of this damn bonus unit.

1 / How the bonus unit works

This tutorial is intended for a programmed 3-ball game.

On the 3 games concerned by this tutorial, Gottlieb installed a scan bonus unit and added a 6th pulse per sequence (4D motor switch), just after the 5th pulse of 4A.

img_1791x-578108c (resized).jpg

On the motor sequences chart of these 3 games, there is an error regarding 4D stacking.

It is not at the start of the sequence but at the end of it, between the last action on 4A and the end of the engine sequence.

diagramme-_moteur-5780fe3WW (resized).jpg

There is also an error in the motor switches list.

4A inside switch is well assigned to the operation of the Add Bonus Unit.

contacts_moteur-5780febWW (resized).jpg

For the 1st and 2nd ball, the bonus unit receives 6 pulses (5 pulses of 4A + 1 pulse of 4D), the 1000 points relay L receives as many pulses of 4A + 4D as there are fallen targets.

So during the motor sequence, the bonus advanced 6 notches and the 1000 point relay L counted from 0 to 6000 points depending on the number of fallen targets.

add-bonus-unit-5780fed (resized).jpg

1000pts_relais-5780ff1 (resized).jpg

So, for a perfectly adjusted machine, the unit bonus counts completely in 2 sequences (6 notches X 2) + a ½ sequence (3 notches) = 15 notches = 5/6 engine revolution.


In 3rd ball, the opening of the Normally Closed contact of K shows the 2D and 3B contacts which are in series with 4A.

add-bonus-unit-5780fed (resized).jpg

This has the effect of giving only 3 pulses per sequence (4A + 2D, 4A + 3B, 4D) on the bonus unit while the 1000 points relay L still receives 6.

add-bonus-unit-2-5780ff7 (resized).jpg

And so 2 impulses for the 1000 points relay L (and 1 on the bonus) give 2000 points per target.

Clearly, per motor sequence, the bonus only receives 3 pulses while the 1000 points relay L still receives 6, the bonus unit counts completely in 1 motor revolution (3 notches x 3 sequences) + 2 sequences (6 notches ) = 15 notches.


The bonuses are counted through the operation of "Bonus score control relay" relay G via 2 essential switches, the G relay lock-in switch and the Normally Closed switch of the 15th position.

bonus-score-control-relay-5780ff9 (resized).jpg

Finally, the bonus unit is reset to zero with each new ball, via a switch of relay P.

reset-bonus-unit-5780fff (resized).jpg

2 / Cleaning of the various elements constituting the bonus unit

The counting of bonuses on the Canada Dry is very precise !

On the one hand, a perfectly functional unit is needed mechanically, no downtime or skating, and on the other hand an efficient counting of 1000 points (L relay perfectly adjusted).

If the 1000-point relay L has a tendency to remain stuck after an impulse or if its motor contacts feeding it are clogged (especially the 4A which is close to the motor cam, and which has the potential to pick up a lot of dirt and fat), there will be anarchy in the count.
If the bonus unit jumps or stalls at times, there will also be anarchy in the scoring.

All this to say that it is necessary:

• Perfect cleaning and adjustment of the 10 + 5 switches of the drop targets (the switch must be closed when the target is shot)

• A 1000-point L relay, properly adjusted and perfectly cleaned switches, especially those with large pads,

• The 6 motor switches perfectly adjusted and cleaned: 4A (inside), 4A (2nd switch), 4D (inside), 4D (2nd switch), 2D (2nd switch), 3B (2nd switch),

If the transformer is set to High, the motor runs faster, which confuses the last 2 pulses (the 5th of 4A and the only of 4D) if the 4D contact is incorrectly set.
This 4D contact must be correctly adjusted, it must close AFTER the 5th impulse of the 4A sequence and BEFORE the start of the 1st impulse of the NEXT 4A sequence.

• Unbroken motor contact blades (particularly the 2D which is often broken and which makes the count disturbed in 3rd ball),

• The perfectly effective set of rivet / pad contacts:
That is to say, well curved pads and not flat when worn, pads sliding perfectly in the guides, clean rivets not hollowed out by wear, a very flexible connecting wire (bridge between the two pads) (not rigid) so as not to influence the sliding of one shoe in relation to the other,

• Perfect adjustment of the three 15th position switches, located behind the bonus unit, in particular the one involving relay G, this contact having to remain closed throughout the bonus count cycle,

• Perfect operation of relay G "Bonus score control relay" which must remain closed throughout the bonus count cycle (in particular the G relay lock-in switch and the 15th position switch mentioned above),

• Perfect functioning of relay K "Double bonus relay", for the counting of bonuses in 3rd ball.

3 / Adjusting the rotating cam

The ZERO position of the unit bonus is indicated by the intersection of the yellow wire and the yellow + blue wire.

came-bonus-unit-5781007 (resized).jpg

Wedge the rotating cam in ZERO position, on the 2nd outside rivet (see pic below), the cam can however be shifted one notch to the right, on the 1st outside rivet; without any impact for the bonus count, since the system is scanning.

img_1782x-578108f (resized).jpg

4 / Adjusting the 15th position switches

These 3 switches must be particularly cleaned and adjusted when restarting the pinball machine, because they are not easily accessible, once the playfield is vertical.

When scanning the rotating cam, it is imperative that the 2 outer contacts remain perfectly bonded throughout the scanning (beware of vibrations), otherwise the count will malfunction.

From the ZERO position and during the ENTIRE scan :

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In the LAST position :

img_1789-5781022 (resized).jpg

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5 / Typical issues

• Slow countdown

The classic case of many Canada Dry and Target Alpha which are never properly repaired, due to lack of knowledge ...

15th position switch and G relay lock-in switch go the green path when fully functional.

If the 15th position switch and/or the G relay lock-in switch come off during the bonus count, the electrical path will be irretrievably taken by 2 additional motor switches (red dotted path), making the count very slow.

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• Generous or miserly count as a bonus in 3rd ball (if game set in 3 balls)

This failure is recurring, you have to have a careful eye to find it !

Indeed, everything is based mainly on 2 motor switches, 2D and 3B, and particularly on the formed switch blades.

The recurrent failure is located at the level of the 2D formed switch blade, which suffers particularly during the many cycles of rotation of the motor.

It often happens that it's broken and then replaced by budding bad repairmans !

Below are 2 pics with the GOOD 2D formed switch blades :

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img_1792-578105c1WW (resized).jpg

This is what we can find !

canada_moteur-5781060WWW (resized).jpg

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I actually had some scoring issues recently when restarting a Canada DRY.

Indeed, the 2D formed switch blades seemed to correspond visually to a normal formed switch blades (ref A-9349).

But it had been manufactured without respecting the correct spacing, which caused a bad counting.

We can clearly see the differences between the 2 formed switches blades.

img_1737-578106aWW (resized).jpg

Please feel free to liven up this post if you have any anecdotes to back it up !

Source :

#2 1 year ago

Wow, thanks for putting this together.

#3 1 year ago

Nice compilation. A few of the 1970s multiplayer Gottlieb games got pretty tricky with bonuses and trying to squeeze one more pulse out of the Score Motor. Here are another couple topics on similar issues:


#4 1 year ago
Quoted from kangourou:

If the transformer is set to High, the motor runs faster,...

I question that. I think the motor speed is governed by the frequency of the AC supply line into the game.

But overall, it's great to have a full write-up of this precedent-setting bonus count system.
.................David Marston

#5 1 year ago
Quoted from dmarston:

I question that. I think the motor speed is governed by the frequency of the AC supply line into the game.
But overall, it's great to have a full write-up of this precedent-setting bonus count system.
.................David Marston

Correct. Motor speed is determined by the AC frequency. I get re-imports with 50Hz motors, and they run faster than normal with our domestic 60Hz. I chuckle when I watch YouTube videos of the Australian guys and their clunky slow-running 60Hz games running on their 50Hz AC. The hum from their games is also very different sounding when one is used to 60HZ AC hum.

#6 1 year ago

Major kudos though to kangourou for compiling this data. He sure knows his way around EMs, particularly the complex '70s multi-player ones!

1 week later
#7 1 year ago

Recently acquired my first EM which is a Target Alpha. I’m still struggling with some minor issues but making headway putting all the pieces together. Once I understand more I’ll probably be able to check this.

1) is this only related to 3 ball play or 5 ball as well? Currently set to 5 balls but pretty easy to roll the score so I expect I’ll move it to 3.

2) are all/most machines not set up correctly from day one? Or is this typically something that happens over time or if maintained incorrectly... ie should I expect my machine has this problem... or need to look for it?

3) as for scoring bonus correctly, i interpret the rules and design to be that the bonus score is only related to drop targets... ie. one bonus per dropped target... 15k maximum or 30K on last ball for double bonus... correct ?


#8 1 year ago

Oh... and 4) this is only related to the final ball extra bonus scoring... or could be a problem with each ball.


#9 1 year ago


My response :

1/It's not the problem if your game is in 3 or 5 balls play.

2/All/most machines are set up correctly from day one but it may become disturbed with time, use or a bad setting.

3/Correct !

4/this can related to each ball

#10 1 year ago

I am in the process of cleaning up and annotating my TA schematics file. I was going to ask if others can confirm the error in the TA sequence chart (Not just Canada Dry) but searched and found another post that indicates it’s incorrect in Solar City, and mine on TA still shows it at beginning of cycle and has not been updated. I’m going to modify it on my schematic.

Great post! Also helps me understand how multiple motor switches work together as AND and OR functions which will help me debug other problems. Very kewl.


6 months later
#11 1 year ago

Thank you!!! You saved my sanity as I just could not figure out how to get my double bonus working. I had "fixed" my 4D switch stack to match the schematic when also fixing the 3D stack (which had actually broken); and that fixed other issues I had, but double bonus just wasn't working.

As much as I tried to figure out how it was supposed to work I could not see how the counts per 1/3rd revolution could get a proper double bonus count. It make soooo much more sense when there's a 6th count! Now my Target Alpha is working great.

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