(Topic ID: 84258)

CftBL - I think I need to replace my transformer

By mjwilliams

9 years ago

Topic Stats

  • 10 posts
  • 6 Pinsiders participating
  • Latest reply 8 years ago by TomGWI
  • No one calls this topic a favorite


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#1 9 years ago

I am hoping to get additional direction before I plunk down the cash for a new transformer. I've been chasing this ghost on and off for better than a month. The original problem resulted in having to replace the power driver board. After I put the new board in and replaced all the Molex connectors that connected to the new board, the pin would randomly reboot after a couple minutes of play. I figured out that I had a GI problem. The machine behaves perfectly normal if I disconnect the connector going to J115, which is traces back entirely to the GI circuit off the transformer. I thought it was the board or one of the outbound connections from the board (J119,120, & 121) but those all checked out fine.

I finally thought to check the voltage coming out of the transformer. I checked the continuity of each circuit back to the 9 pin connector on the transformer. I made my measurements of the GI yellow white circuit by disconnecting the 9 pin connector coming right off the transformer. Three of the pins are only putting out 4.2 volts (those that connect to white/brown, white/orange, & white/yellow) while the other four pins are only putting out 1.3 volts (yellow, brown, green, & orange). I thought this was supposed to be a parallel circuit (in the transformer) so they all should be putting the out same voltage(?)

According to be schematic all the connections on J 115 are supposed to be a 6.8 V. I figure unloaded i should probably be seeing greater than 7V on the circuit, not the oddball voltages I measured. (I also checked it with my oscilloscope and the signal is clean and steady, just really low voltage.)

Any thoughts about something else I could be missing? I would appreciate any feedback!

#2 9 years ago

been working on pinballs since 1998....a LOT of them and have never seen a bad B/W transformer.
Not saying it's not your problem, but I would be VERY surprised if it is bad.

Is the power driver board you installed a rottendog new one, a repaired old one? or?
Resets are usually caused by the 5V watchdog circuit on the CPU board. Perhaps removing that connector is taking some stress off the board and stopping the resets, but highly doubt the GI is going to CAUSE the resets.

#3 9 years ago

your transformer is most likely fine.
need to set meter to ac voltage and measure across each matching lead, white/yellow-yellow, white/brown-brown.
I think you need to look elsewhere for your reset problems.

#4 9 years ago

Usually there is a connector which goes between the CPU and the Driver board. If you have 5 volts at the driver board you may have less going to the CPU causing the reset. I had a similar problem with my BSD where it would randomly reset. It was the connector going to the CPU that went bad. You can measure the voltage at the Capitol on the CPU. If you have less than 5 volts there the connector is the problem.
Recheck the connectors between the 2.
Are the wires in the right place? Maybe a wire got switched if you replaced the connectors in that area. Check the connector to the CPU and replace that.
A good source is the pinball ninja website. You have to donate $20 but the owner has these problems documented and can help.

#5 9 years ago

check pinwiki look for the reset section. g.l. joe

#6 9 years ago

If you look in the WPC schematic manual (NOT the game manual...Everyone needs one of these if you don't have one).

One side of the transformer circuit is the WHT/BRN - WHT/ORG - WHT/YEL... pins 2,3,4,5,6 and the other side is BRN - GRN - ORG - YEL/WHT... pins 1,7,8,10,11,12. It should be 6.8 volts AC across these two sides of the circuit.

I agree with the guys above that it's rare to see a bad transformer. From what I get from your discription, you might be measuring your transformer voltage wrong, and to me, the reset should be a separate issue to the GI problem. Double check the molex connection you did to be sure you did it correctly. It's real easy to mix up wires..... Trust me!!

#7 9 years ago

I have to check this out tomorrow because it's an 18 hour day at work today, but I will follow up with answers and a better description tomorrow night. Thank you for your help!!!

#8 9 years ago

Yay! (and Dangnabbit!)
tullster and TomGWI got it right, I mixed up the wires when I redid the MOLEX
At least I don't need to replace the transformer.

FYI it is a brand new Rottendog board
Now I am back to the original reset problem.
Off to pinwiki
Thank you guys!

#9 9 years ago

I would check the connectors between the CPU and the driver board. I bet you are losing voltage through the connectors. Look at 4.8.9 on PinWiki or Repair 753 on PinballNinja site on how to test and fix the problem.
I was having reset issues on my BSD and it had to do with the connectors between the CPU/driver board. Even a slight drop in the 5 volts will cause the CPU watch dog chip to reset the game.

1 week later
#10 8 years ago

Not sure if you fixed this but this is what I was talking about:


Quoted from HHaase:

Looked at cyberninja's machine today. Replaced a stressed varistor and j101 connector housing, which cured a boot-up delay problem. That gave a solid 4.95v at the power driver board, but was getting intermittant voltage that varied from 4.88 to 4.74 at L1 on the cpu board, and was sti resetting. New connectors a j114 and j201(?), and now giving a solid 4.9v at L1, was no longer resetting when I left, and I await a more long term report.

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