EM Transformer Questions - Gottlieb Big Top

(Topic ID: 188950)

EM Transformer Questions - Gottlieb Big Top

By essmeier

1 year ago

Topic Stats

  • 17 posts
  • 6 Pinsiders participating
  • Latest reply 1 year ago by essmeier
  • Topic is favorited by 3 Pinsiders


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There have been 3 images uploaded to this topic. (View topic image gallery).

big_top_schematic.pdf (PDF preview)
transformer (resized).png
transformer_labeled (resized).jpg

#1 1 year ago

Trying to bring a game back from the dead (Gottlieb Big Top.) At power-up, nothing happens.

Before I do anything else, I want to check the transformer, but the labeling on this one has me a bit confused, so I'm not sure what voltages I should be seeing or where I should be seeing them.

This particular transformer doesn't have everything labeled, so I'm not sure what's what.

On the top, I've got terminals labeled "High," "Normal," and "Start," along with two terminal that are not labeled.

On the bottom, I've got two terminals that are not labeled. The one that I've noted as "3" in the attached image has a line from the power cord coming into it.

I need to test the output voltages, but I'm not sure where to put the leads. Is the lug labeled "start" the one that's often labeled "common?"

I AM getting 110 volts between "3" on the transformer and "A" on the fuse, so our fuse, cord and power switch are good.

In my previous EM adventures, I've rarely needed to deal with transformers at all, and when I have, everything's been labeled.

I should be able to see three voltages - 110 volts (input), 6 volts, and 24 volts (output). Between which points should I be checking to see those voltages?


transformer_labeled (resized).jpg

#2 1 year ago

Solenoid High Tap - A few volts higher than normal solenoid voltage designed for when your house had line voltage that was too low back in the 60's/70's, it gives a stronger kick to the solenoids when used on correct line voltage and is not recommended to be used in this situation - you'd switch the solenoid wire to this lug and leave the other lug unused, one should ALWAYS be empty

Solenoid Voltage (24v) - Powers all coils

Start sequence tap - [edited] CORRECTION: 115V for the start sequence (Relay bank, and later drop-target reset banks) - this is here because if the machine was overseas it would still need to generate 115V out of higher voltage like 220V rather than just be an equivalent, these large coils were made for 115V and never had "sister" coils for 220V and the like, so it is needed in the machine regardless

Lighting (6v) - Powers all playfield and backbox lighting, note as they each have a different fuse down the line how there is a seperate line for each circuit

Ground - Self-explanatory, read below, this lug is likely only for lighting ground/common

With how many wires are going to the START lug, I wonder if this is used as some sort of solenoid ground/common (especially since it's black wiring). I honestly haven't ever needed to mess with that enough to know, sorry. But this should set you off in the right direction.

transformer (resized).png

#3 1 year ago

Let me correct myself, the START lug is (as I originally thought) 115V for the start sequence, used in any reset bank coils (115v rated/powered), and later in the 70's on drop target banks.

This is needed on the transformer because overseas they use higher voltage, but the games still used 115V coils (not adjusted/made differently for like 220V in Britain, etc.). So if they used a different line voltage, the voltage would need to be converted down.

#4 1 year ago

A multimeter will answer all your questions. Establish a ground and your meter will give the voltages.

#5 1 year ago

"A multimeter will answer all your questions. Establish a ground and your meter will give the voltages."

My questions concerned where to put the leads from the multimeter in order to test the respective voltages as half of the lugs on the transformer aren't marked.


So, points "4" and "A" on my image should be common, as they both represent "hot" line voltage, right? If I'm reading 110 volts between points 3 and A, shouldn't I also be reading 110 volts between points 3 and 4?

I'm concerned that I may not be getting 110 volts at the input side of the transformer, perhaps due to a problem somewhere between the fuse and the transformer.


#6 1 year ago

From memory, i believe the following is correct... (though i easily could be wrong!)

the "start" tap is the center tap. Everything but 120 volts is reference to this lug. Meaning when measuring transformer AC outputs, the center tap is where one of the DMM leads attaches.

The "high" and "normal" are the coil voltages. 28 volt AC and 30 volt AC respectively.

The "1" and "2" taps are light voltages. Gottlieb used 6.3 vac for everything except for the coin door, in which the voltage "2" is about 5 volts. Why did they do that? Because the lower voltage will keep the coin door lights alive without burn out for a really long long time (though obviously not as bright.) They did this because it's a PIA to change the coin door lights, and operators generally never did it. Without coin door lights, the coin slots look "dead" and in theory, the game does not earn as much.

Lugs "3" and "4" are AC voltage in, meaning 120 volts. If you put your DMM on these two lugs, you should get line voltage (that is, don't use center tap as a reference.)

Note the above transformer is not designed to run at anything other than 120 volts. Mean Gottlieb used an entirely different transformer for 220 volt applications (with different lug designations.)

To verify my theory, just use your DMM set to AC voltage to check. You'll know quick enough if i'm right or wrong...

#7 1 year ago

I'm seeing 0 volts between points 3 and 4. If I'm reading the schematic correctly, the "red" wire at point 4 first has to go through the shutoff switch, the bounce switch the anti-cheat switch on the coin door and a switch on the start relay, though that switch shows as normally open.

Not sure what's happening (or not) here.


#8 1 year ago

If your missing voltage between 3 and 4. Looks like your not getting voltage to the transformer.

#9 1 year ago

I'd think so, but I'm not measuring voltage between 3 and 4 on my Slick Chick either, and that game works.

#10 1 year ago

Don't mean to be silly but, is the games power switch on?

#11 1 year ago

Just put your hand on the transformer. Cold no voltage. Warm voltage. Touch it in the wrong place and it will shock you!

#12 1 year ago

Look at the schematic and match up the wire colors.

#13 1 year ago
Quoted from HowardR:

Look at the schematic and match up the wire colors.

Not much help on a 50 year old game where nearly every wire is the same color.

Quoted from cfh:

Don't mean to be silly but, is the games power switch on?

Previously addressed, but yes, it's on. I'm getting power through the switch and through the fuse, but beyond that, it doesn't seem to be getting to the transformer.

The shutoff switch, anti-cheat switch and bounce switch are all closed, so I'm not sure where the hangup might be. I've attached a copy of the schematic in case anyone feels like having a look.



#14 1 year ago

Hi Charlie
does Your pin has paper-tags telling the name of the relays ?
DANGER - You are handling 110VAC. In Your schematics I see a "Switch on S-Start-Relay" and a "Switch on R-110-Volt-Hold-Relay" (((the Coil on R-Relay is feeded 24VAC --- BUT it does HOLD the circuitry of 110VAC))).

Please use a wooden stick (insulation) and gently press --- and a quarter of a second later let go: Press the armature (anchor-plate) of the S-Relay. I hope for luck so the pin comes to life and starts a new game. Also (wooden stick): Press the armature of R-Relay. Keep Your hands of everything metal. Want a friend to be ready to unplug the 110 main power cord ? Greetings Rolf

#15 1 year ago

Transformer is now known to be good. The anti-cheat switch on the coin door appeared to be closed, but wasn't. That was preventing power from getting to the transformer. I've adjusted the switch so it is not closed.

The machine won't start a game when I press the coin switch, but when I pressed the start relay, the score motor began to turn (continuously) and all the lights on the playfield and the head came on.

The score reels make no attempt to reset.

I have labeled my relays; none of them were labeled when I received the game. My restoration of this game is a story for another thread, and I'll share that after I get it working. There isn't a single component on this machine that hasn't been completely disassembled, so I've likely got 50 problems to solve before it will play a game.

For now, at least I know I have power.

#16 1 year ago

Hi Charlie
great - You found an fault --- progress.
Look here http://www.ipdb.org/showpic.pl?id=286&picno=50754 , Your schematics does talk about "Bank Reset Coil" and "Sequence Bank Reset Coil" - please see the list in Your schematics - the relays mentioned - do You find them on the banks we see in the ipdb-picture ?

I live in Switzerland, South of Germany - it is 15 minutes after midnight --- time to go to sleep, till tomorrow, greetings Rolf

#17 1 year ago

Now that it's powered up, I'm having trouble figuring out the startup sequence and I've got questions about the score motor.

I've started a new thread about that here, in case anyone would care to help:



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