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(Topic ID: 205971)

DE Simpsons flipper issue

By mark-mco

2 years ago

Topic Stats

  • 7 posts
  • 4 Pinsiders participating
  • Latest reply 2 years ago by u2sean
  • No one calls this topic a favorite


Linked Games

#1 2 years ago

New to the forum . Did some searching on this first and did a little troubleshooting. I've had a DE Simpsons for 20 years without a problem. Powered it up a few days ago and the left and right flippers are extremely weak. Also, the laser kickback solenoid actuates when I press either flipper button. Checked fuses on PPB and F5 was blown, so apparently I'm not getting 50 volts to the flipper board. Replaced it with a 5 amp slo-blow and It immediately blew when I powered it up. All three of these coils measure 3.9 ohms across leads so which I'm assuming is normal. I do have a 40 page manual on this which seems complete, although the schematics for the PBB and Power Supply Board is a separate page from some other source. Any suggestions on how to proceed?

#2 2 years ago

I think you may have a bad bridge rectifier blowing F5. That fuse is there to protect the transformer. The 50 volts AC comes from the transformer, through F5 and is converted to 50 volts DC by the bridge rectifier. If the bridge is shorted it will blow F5. Test the bridge rectifier.

#3 2 years ago

Thanks for the quick reply. I'm assuming you are referring to BR1 on the PBB. I tested it using the following procedure:
- Put DVM on diode setting
- DVM red to bridge '-'.
- Verify conduction to both AC terminals.
- DVM black to bridge '+'
- Verify conduction to both AC terminals.
- DVM black to bridge '-'.
- Verify open to both AC terminals.
- DVM red to bridge '+'
- Verify open to both AC terminals.
I measured between 505 and 520 on all four steps. As the last two should show open, does this indicate a bad BR? Or is this due to me testing it while it is still installed in machine? Do I need to remove the BR to correctly test? I apologize if I'm asking basic questions, but I'm in the newbie category as far as troubleshooting electronics. Played around with bread-boarding circuits back in the mid 70's. But unlike riding a bike it seems it doesn't come right back to me. And while Google is great

#4 2 years ago

Yes BR1 on the PPB. The test results may not be showing a bad BR1. The next step is to put a new fuse into F5. Disconnect connectors J7 and J3.This is the 50v output and ground from the PPB. Power on the game. If the fuse blows there is definitely a problem on the PPB.

#5 2 years ago

Thanks for reply. I disconnected J7 and J3 and the fuse does not blow when powering up. I checked the voltage on these terminals and I measure 75. Shouldn't this be 50? Then just to check, I powered off and reconnected these and powered it back on. As before, the fuse blew again. I also noticed that the laser kickback solenoid fires when I power it on and the fuse blows. I'm don't recall if this normally happens on power-up.
On a related note, does anyone have pages 41-57 of the manual for this game? Mine manual appears to be original, but only has up through page 40 while the table of contents show up to page 57. Unfortunately, all the schematics for the boards are contained on these pages. Or perhaps a manual from a similar DE game from that time frame.

#6 2 years ago

The simpsons on ipdb doesn’t have those pages either. The BTTF manual does though

#7 2 years ago

The Laser Kick is powered by the large TIP-36C transistor on the power board - Q5. If that's shorted then it'll lock on that coil. The coil itself may be internally shorted and/or have a bad diode. I would replace that TIP and disconnect the laser kick coil temporarily - see if things work. If so, test that coil and diode.

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