(Topic ID: 207553)

Gottlieb Sys1: Replace dead small transformer with LED displays & power supply

By ForceFlow

3 years ago


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  • 23 posts
  • 8 Pinsiders participating
  • Latest reply 58 days ago by northvibe
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#1 3 years ago

This discussion came up in the "project games for sale" thread about what do to when a system 1 game has a dead small transformer since small transformers (B-17921) are difficult to find.

The small transformer carries a bit more than just the high voltage for the displays:
The two transformers convert the 120 volts AC input to other voltages needed for the game. [...] The small transformer outputs the main score display voltage (60/42 volts), the computer board voltage (12 volts which ultimately ends up as +5 volts), and the score display offset/reference voltages (8 and 4 volts).
Source: http://www.pinrepair.com/sys1/

It sounds like can use Boston Pinball's LED displays:

http://www.bostonpinballcompany.com/displays.htm

According to boston pinball, the displays do not require 69vac (60vdc & 42vdc), the offset voltages, or 5vac.

The (original) MPU requires +5vdc and -12vdc at J1.

So, it sounds like you can use an arcade power supply for the +5vdc and -12vdc, and bypass the Gottlieb power supply.

Desolder the wires for the small transformer. Put ring terminals on the hot & common wires, and connect those to the power supply. Add a ground wire from the power supply ground terminal to the EMI filter's middle terminal. Get a J1 connector (09-01-6061), and connect +5vdc and -12vdc to the appropriate pins.

1: Spare
2: -12vdc
3: DC GND
4: DC GND
5: +5vdc
6: +5vdc

Since it's not common to have -12vdc on arcade power supplies (but they are readily available on ATX computer power supplies), options are limited. There are -12vdc 0.5A, 1A, and 2A Mean Well power supplies available:

https://www.digikey.com/products/en/power-supplies-external-internal-off-board/ac-dc-converters/133?k=&pkeyword=&pv1527=6&FV=fffc074a%2C2dc1d7b%2Cffe00085&mnonly=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25

I'm not certain on how much draw there actually is on -12vdc.

The pinout of the 4-digit display uses +5vdc at pin 18, which is fed by the MPU (from J3) and isn't a problem.

The pinout of the 6-digit display might be problematic. It appears to take +60vdc at pin 17 from the Gottlieb power supply, and uses a 15k 1/2w resistor to drop to +5vdc. I'm not sure yet how exactly the boston pinball displays handle this. Here's two versions of the original display schematic:

pasted_image (resized).pngpasted_image (resized).png

Any thoughts?

#2 3 years ago

In looking at the installation documents, it looks like the boston pinball displays are powered by a separate power supply, with a power adapter plugged into the service outlet. The 69vac line fuse is removed.

http://www.bostonpinballcompany.com/install.htm

#3 3 years ago

What is the -12v used for?

#4 3 years ago

Trying to zoom in on the BPC display boards, and they look like they have GND, 5V and 4V silk screened on their J2 and maybe the same on J3?

Quoted from zacaj:

What is the -12v used for?

The -12V is for the original MPU board - something about the Rockwell chips needing this voltage.

#5 3 years ago
Quoted from zacaj:

What is the -12v used for?

http://www.pinrepair.com/sys1/#tools

Looks like it's involved in some way with the spider chips, some transistors, and digit/segment output lines for the displays.

#6 3 years ago

Technically, the 11660 (Rockwell PPS-4/2) runs on 17VDC. But, by using somewhat standard power supply inputs (+5 and -12) it uses various components to interface with 5V logic.

#7 3 years ago

From what I can tell, both the NiWumpf and Pascal Janin PI-1(X4) boards only use +5V so the -12 is not necessary if you have already dumped your original Gottlieb MPU board.

#8 3 years ago
Quoted from CactusJack:

From what I can tell, both the NiWumpf and Pascal Janin PI-1(X4) boards only use +5V so the -12 is not necessary if you have already dumped your original Gottlieb MPU board.

Good to know

[edit]: I looked into the boards a little bit. I sent David an email about his board. And since I'm not sure if the Pascal board requires all the original voltages or not in order to boot, I dropped him an email as well.

#9 3 years ago

I got confirmation that the nii-wumpf MPU only needs +5vdc.

#10 3 years ago

Also the LISY1. More on that later...

#11 3 years ago

hello everyone

my PI-1 board uses +5V only.

my all-in-one PI-1 X4 board uses 11VAC and 14VAC taps from the small transformer, but not the 69VAC.
therefore it could still run on a damaged transformer whose 69VAC tap often blows due to reverse insertion of A2P1 connector on the original GTB power supply..

in addition to this, my all-in-one PI-1 X4 board generates enough current on the 12VDC output available at the screw-clamp connector J1, so that it can directly power Boston Pinball's excellent displays without need for an additional power supply block.

see the attached picture: direct power to the displays or to the dimmer provided with each displays kit.

Connect_PI1X4_eng_s (resized).jpg

#12 3 years ago
Quoted from Pascal_J:

my all-in-one PI-1 X4 board uses 11VAC and 14VAC taps from the small transformer

Would you be able to use these 12v and 15v transformers along with your PI-1 X4 all-in-one board?

http://www.antekinc.com/an-0212-25va-12v-transformer/

http://www.antekinc.com/an-0215-25va-15v-transformer/

Or would the extra voltage for each circuit be too much?

8 months later
1 month later
#14 2 years ago

I’m gonna bump this. Has anyone had to do what force flow is describing to skip the small transformer?

1 year later
#15 1 year ago
Quoted from northvibe:

I’m gonna bump this. Has anyone had to do what force flow is describing to skip the small transformer?

I ended up selling my joker poker that needed the small transformer replaced. But I had installed Boston pinball led displays and a pascal PI-1 all in one board. So the 69v was not needed, however there was another voltage needed, 14v I think from the small psu.

5 months later
#16 7 months ago

Alrighty! Fixing my friend's two gottlieb sys1's and a neighbors sys80a and it seems like we may have some bad transformers. So I'm back in this dead small transformer solution and I think I've been narrowing it down to parts and how etc. I'll document and list as much info as I can after I get this going. There are a few ways to do it and parts to use, so I hope we can make it fairly easy for anyone else in the future and stop the parting out of old sys1's that have a bad transformer.

Roller disco - no power from 69vac, 42vac and 5v, 12v. no displays or volttage to the head. Only playfield and backbox lights. Resistance testing of small xformer is showing low resistance on all windings except 69v and 115v.
Dragon - need to get more testing
jakes to open - no displays or volttage to the head. Only playfield and backbox lights.

4 months later
#17 3 months ago

Another bump. I built 5VDC LED displays and have a NiWumpf for my Close Encounters. My manual and schematic are currently MIA. If I only need 5VDC, can I ditch the backbox power supply and my dead small transformer and just add a 5VDC power supply? Does the backbox power supply just feed the MPU and the displays?

#18 3 months ago
Quoted from toblave:

Another bump. I built 5VDC LED displays and have a NiWumpf for my Close Encounters. My manual and schematic are currently MIA. If I only need 5VDC, can I ditch the backbox power supply and my dead small transformer and just add a 5VDC power supply? Does the backbox power supply just feed the MPU and the displays?

in theory yes. You'd power the displays.You'd have to see what the cpu board takes for power 12 and/or 5?

1 month later
#19 59 days ago

Hey gang,

I am very new to pinball and recently got a Sinbad machine. Being an idiot, I plugged the unkeyed power cable in upside down and completely melted my Small Transformer - what a design!

Someone had already replaced the main board with a Ni-Wumpf and after reading all the comments on this thread and the pinwiki, attempting to bypass the Small Transformer seemed like the best option (especially when they are so hard to find). So I ordered a Boston Pinball Company LED kit v8, which arrived yesterday.

Here is what I did today:

- Cut all the wires to the small transformer, terminated them all and then removed the small transformer
- Unplugged and removed the power board, which was toast. I also desoldered the A1-J1 connector from the board so I could reuse it
- Removed all the old displays and installed the new LED displays
- Installed the Brightness Control Board as instructed (except there is no power board to plug A2-J3 in to - come back to this)
- My machine didn't have a service port wired in for some reason, so I hard-wired a small powerboard in temporarily (I will swap this for a proper double power point later)
- Found an old 5V/2A switching DC power supply, plugged in to power board and checked the voltage and polarity. Then I soldered the +5 to pins 5-6 and ground to pins 3-4 pins of the A1-J1 connector, which sorts out the Ni-Wumpf
- While I was there, I also added two more leads from the +5 and ground, which had to be connected to pin 7 and pin 5 respectively on A2-J3, which sorts out the displays
- Plug in power pack supplied with the LED kit and connect it to the Brightness Control Board

Machine boots and plays! Displays are super sharp, couldn't be happier.

Just wanted to say thanks to everyone who commented - I would probably still be looking for a Small Transformer otherwise

#20 58 days ago

Good to hear that someone was able to do this successfully

#21 58 days ago
Quoted from fileoffset:

Hey gang,
I am very new to pinball and recently got a Sinbad machine. Being an idiot, I plugged the unkeyed power cable in upside down and completely melted my Small Transformer - what a design!
Someone had already replaced the main board with a Ni-Wumpf and after reading all the comments on this thread and the pinwiki, attempting to bypass the Small Transformer seemed like the best option (especially when they are so hard to find). So I ordered a Boston Pinball Company LED kit v8, which arrived yesterday.
Here is what I did today:
- Cut all the wires to the small transformer, terminated them all and then removed the small transformer
- Unplugged and removed the power board, which was toast. I also desoldered the A1-J1 connector from the board so I could reuse it
- Removed all the old displays and installed the new LED displays
- Installed the Brightness Control Board as instructed (except there is no power board to plug A2-J3 in to - come back to this)
- My machine didn't have a service port wired in for some reason, so I hard-wired a small powerboard in temporarily (I will swap this for a proper double power point later)
- Found an old 5V/2A switching DC power supply, plugged in to power board and checked the voltage and polarity. Then I soldered the +5 to pins 5-6 and ground to pins 3-4 pins of the A1-J1 connector, which sorts out the Ni-Wumpf
- While I was there, I also added two more leads from the +5 and ground, which had to be connected to pin 7 and pin 5 respectively on A2-J3, which sorts out the displays
- Plug in power pack supplied with the LED kit and connect it to the Brightness Control Board
Machine boots and plays! Displays are super sharp, couldn't be happier.
Just wanted to say thanks to everyone who commented - I would probably still be looking for a Small Transformer otherwise

What displays did you use? What driver board? Congrats on having a sys1 with no small transformer! We’ve been waiting for confirmation

#22 58 days ago
Quoted from northvibe:

What displays did you use?

The boston pinball displays. I linked to them in the first post.

Quoted from northvibe:

What driver board?

The driver board doesn't matter since it doesn't connect to the small transfomer. Any original or aftermarket one will do.

#23 58 days ago
Quoted from ForceFlow:

The boston pinball displays. I linked to them in the first post.

The driver board doesn't matter since it doesn't connect to the small transfomer. Any original or aftermarket one will do.

Ahhh sure, I didn’t read it all just skimmed.

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