(Topic ID: 161205)

Why am I getting 36vac for my gi on my Robocop?

By Chochi_ca

2 years ago

Topic Stats

  • 28 posts
  • 10 Pinsiders participating
  • Latest reply 2 years ago by thedefog
  • Topic is favorited by 1 Pinsider


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#1 2 years ago

I am puzzled. I only have my 6.3vac power off my transformer to my power supply board. I am getting 36volts supplied to cn8 pins? How can this b when I only have 6.3v supplied?

#2 2 years ago

Can't see how that is possible to have 36 volts on CN8. You must be measuring something wrong or have something plugged in wrong. Can you post a picture of the power supply connected?

What part of the game are you having a problem with?

#3 2 years ago

This is my power supply. I match up white to white/yellow from transformer and yellow to yellow. When I test btw yellow and yellow/white from transformer without connecting it to the board. But when I connect it I get 36v at pins 1-4 at cn8 and 31vac at 5-9. No other connections are made a the power supply. I'm testing from ground to each pin. I have even swapped power supplies and get same readings?


#4 2 years ago

When I test the transformer btw yellow and yellow white without connection to board I get 6.3v

#5 2 years ago

31V is your coil voltage. Are you sure those are the pins that drive your GI? Also did you check the board for a short between the GI and coil voltages?

#6 2 years ago

I am getting these 36vac readings with only the 6.3 supply from the transformer plugged in. I even removed the other square plug that supplies the other voltages to the machine from the transformer. Still getting the 36v reading. I am testing at the gi pins at cn8. Could there b voltage leaking in the transformer? Should i test btw both yellows and both yellow/whites from the transformer for voltage? Or do i have the wires mixed up at cn9(yellow and white wires)? or any other ideas?

#7 2 years ago

I've have to see how you're measuring it. You can't get 36V from a 6.3V feed without some circuitry to boost the voltage. It just isn't possible. I'd speculate it's a measurement error.

#8 2 years ago


#9 2 years ago

just put automotive bulbs in and you're fine.

Seriously if your getting coil voltage over the GI band, you have a short somewhere. might be a trace on a board under a new socket or something.

#10 2 years ago

Ok will check it again. I am a newbie and appreciate the responses. I put my black lead on grounding screw and the red on each make pin on connector c8. Is this not the way to test?

#11 2 years ago

Lol yes I'm the one that had the car battery charger running the gi. But I think it was supplying to high of voltage. Bulbs lit up like super brights! So once I removed the charger I lost all my gi

#12 2 years ago

You can't do voltage check off the ground.

#13 2 years ago

let me rephrase that, you can't read AC voltage off the DC ground.

#14 2 years ago

I just checked the IPDB manual and it has very little to offer as far as schematics go...

#15 2 years ago

You're measuring the transformer, but wouldn't the system's power supply take 120V and make it into 36V for coils (like it does for displays, etc.)? Did they still use it off of the transformer in those newer games too?

#16 2 years ago

Did you recently shop out your game or take the boards out? It's possible you have something plugged in wrong under the playfield or at a connector and that's causing incorrect voltage to be sent where it's not supposed to go.

Not that I've ever done something like that myself.

#17 2 years ago

I recently bought the machine and I am attempting to shop it out. So puttin the black lead of my meter on a grounding screw(that attaches to the back plate is not the correct ground? Something def could b wrong with under the playfield. What should I b looking for? Where to test for a short. It seems there is one because soon as I power on the Machine with cn8 plugged in and j5 my gi fuses on the ppb board all blow. The previous owner was using a car batter charger solder to power the gi underneath lol. The cn8 connector was burnt and unplugged. I repaired that connector and verified the wiring on the j5 connnector on the pcb board. I do have more schematics then what is on ipdb. I can include pics of those as well?

#18 2 years ago

I am unsure about the input wiring of my 6.3 volt yellow and yellow/white wires on my power supply board the schematics contradict my current wiring. I'm scared to switch them without confirmation.



#19 2 years ago

When I plug this same power supply board into my high speed wired the same way yellow-yellow and white/yellow to white/yellow my gi works in the high speed

#20 2 years ago
Quoted from Chochi_ca:

The previous owner was using a car batter charger solder to power the gi underneath lol.

That's one way to do it without fixing the original problem!

You're doing a great job trying to find the source of the problem. There has to be some stray voltage getting in your line from something on that board, and it's confirmed by your voltage measurements and the fact that you're blowing the fuses.

Take a really close look at the entire path of the circuit(s) in question. Something as small as a tiny piece of misplaced solder can cause this type of behavior.

#21 2 years ago

You aren't measuring the voltage correctly.

AC is measured differently than DC. Check from pin 1 to pin 9 on the 9 pin connector with pin #5 removed.

#22 2 years ago

Ok I measured the voltage the proper way. And it measures 6.3vac btw pin 1 and 9. Thanx! I have been banging my head against the wall. lol. So now I know I got proper voltage. But I still blow fuses. I noticed something else. There is what looks to b blue speaker wire that ran from the solder points that were attached to the battery charger positive and negative wires. The wire attaches to the gi at various spots. Should I remove this wire. Refuse and test again? Here r some pics of the hack.




#23 2 years ago

Yep, get rid of that hack and retest.

#24 2 years ago

Fixed!! Got rid of the hack(cause of blown fuses). Also found cracked solder on pins at j5. Thanx to everyone for there help!

#26 2 years ago
Quoted from CaptainNeo:

it was a blown fuse this whole time?

According to what the guy at Super Auctions told me, it's always just a fuse.

#28 2 years ago
Quoted from Chochi_ca:

Fixed!! Got rid of the hack(cause of blown fuses).

It was probably wired for DC external powering, so when the AC was connected on the PSU connector, Pop, there goes a AC line to DC ground and a blown fuse to protect it. I'm glad the right value fuse was in place!

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