(Topic ID: 127625)

System 11A, what drives the flipper relay?


By dri

4 years ago



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  • 14 posts
  • 5 Pinsiders participating
  • Latest reply 4 years ago by johnwartjr
  • Topic is favorited by 1 Pinsider

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Williams_System-6_Driver-Board_schematic.pdf (PDF preview)

#1 4 years ago

I'm starting to see the end of the tunnel of a long shop job of an F-14. The previous owner(s) had stuck a piece of cardboard in the flipper relay (K1) to keep flippers engaged at all times. I blindly replaced the relay thinking it was the relay that was toast. For kicks I measured the old relay for continuity in the coil and it buzzed immediately realizing that there's something else that's broken.

I can't really make out what fires the coil inside the relay. One thing that had me thinking is that I could see that there's a diode for the coil (D2 according to the schematics) but there's a tiny resistor there instead and it's next to the battery. This must be a typo, right? Because the closest diode is D3 just above it.

I only have a cheap scan/reprint of the manual and I'm not sure I have the whole story in mine.

Thanks!

#2 4 years ago

Are you sure this new relay is a 5V (or 6V) DC relay?
The little transistor (Q13) in front of the relay is used to switch it on.
You can use this redrawn file from a System-6 (Fire Power), as the schematic is (nearly) the same.
Look in the lower right corner for the flipper relay.
Williams_System-6_Driver-Board_schematic.pdf

#3 4 years ago
Quoted from Inkochnito:

Are you sure this new relay is a 5V (or 6V) DC relay?
The little transistor (Q13) in front of the relay is used to switch it on.
You can use this redrawn file from a System-6 (Fire Power), as the schematic is (nearly) the same.

Thanks for the schematic. I'm pretty sure the new relay is the correct one. I will try change the transistor and diode. Is it OK to substitute a 2N4401 with a 2N5401? That's what I got at home now.

Some of the ICs on this board have been swapped out at one point, I'll see if I can trace some bad solder joints on those too.

#4 4 years ago

Oh, I realized who replied. Thank you for your excellent design of the fuse/bridge/capacitor board. It fit like a glove in my F-14!

#5 4 years ago

Changed diode and transistor. Still dead.

#6 4 years ago

Those transistors are not the same.
The 2N4401 is a NPN and the 2N5401 is a PNP.
So it will not work.
You really need a 2N4401 transistor.

#7 4 years ago
Quoted from Inkochnito:

You really need a 2N4401 transistor.

Yes, I picked up a 2N4401 at RS as I found out you couldn't substitute.

#8 4 years ago

Bump...

#9 4 years ago

Theres a 7402 before the transistor that can fail and cause the relay to be energized at all times. But you should really test it with a logic probe instead of blindly replacing it.

#10 4 years ago
Quoted from johnwartjr:

Theres a 7402 before the transistor that can fail and cause the relay to be energized at all times. But you should really test it with a logic probe instead of blindly replacing it.

Yep yep. The 7402 that turns on the 2n4401 can and does fail. The 2n4401 is usually bad as well when the 7402 relay output is bad.

#11 4 years ago

Thanks! There's been replacements of the 7402 before as they're in a socket. I've ordered a new 7402 and will blindly do that. The 2N4401 and diode have already been replaced.

#12 4 years ago

Sounds like it's nearly time to seek out your favorite PCB repair shop and send the board in rather than possibly create more problems with it and maybe rendering it unrepairable.....

#13 4 years ago
Quoted from Homepin:

Sounds like it's nearly time to seek out your favorite PCB repair shop and send the board in rather than possibly create more problems with it and maybe rendering it unrepairable.....

The board is in pretty crappy shape and hovering a rottendog replacement. I brought the board to PAGG this weekend but couldn't get any help. Sending it to K's Arcade regardless to be tested but thought I just swap the 7402 since it has a socket.

#14 4 years ago

There are 2 7402s in the special solenoid/flipper relay section. The one that controls the flipper relay is U50.

If it's socketed, it's an easy test, but if it's not, it's an almost equivalently easy test with a logic probe

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