I'm following Vid's guide on getting tech help, so first the cut and paste part:

Name of game, manufacturer and year: Williams F-14 Tomcat, '87

Did it ever work in your Possession?: Yes. Worked with no problems for about a year and a half. After the first incident, it went another 11 months before blowing again (more about that below).

Did You Run the Diagnostics?: Not an option in this case. Heard the sound of sizzling electronics and shut it off.

Where did the game come from?: Some guy in Baltimore.

Have needed MODS been done?: Lighting is LED except for flashers. I've added a few LED strip lights as well.

Are any aftermarket boards installed?: No.

What was the last service you performed?: Had board worked on a year ago.

Battery Corrosion: No. External battery pack.

LED or Incandescent lighting?: LED except flashers

Blown fuses: Flipper fuse blew

Smell: Yep.

Obvious Past Work Performed:Details below

Do you have a Volt Meter?: Yes, but I'm only competent at using continuity/diode mode

Can you solder?: Mechanical things, yes. Boards I stay away from.

Location: Greenfield, MA

Last spring, I was playing f-14 tomcat, and I noticed something weird was going on with the diverter; after a confused minute or two, smoke was coming out of the game! I turned it off, and the lower diverter coil was totally smoked, plus the sick smell of hot electronics was coming from the back box.

Like a dummy, I halfass diagnosed the problem and had somebody replace the transistor which controls the lower diverter. Naturally I replaced the coil as well. Long story short, it didn't fix the problem.

I then sent the CPU board to Coin-op Cauldron for proper repair. I have Clive's email and will post after this description. Got the board back, turned on the game, and ZAP. Driver transistor blew out yet again.

Then I took the whole game to a guy more local to me (about an hour and a half away, here in MA). He eventually figured out that the diode on the replacement diverter coil was bad. Another $200 poorer, I now had a working F-14 again.

Fast forward to a couple weeks ago. My friend came over to play by himself (he helped buy the game in the first place and has his own key). Now, I wasn't here to see what happened, but he said the game was acting weird and then the flipper board blew its fuse. Like an idiot (or just not expecting the exact same problem to come up AGAIN), I turned on the game to test things out in diagnostics (after replacing the fuse). It took only seconds to hear the sickening sound of things frying on the board. Sure enough, driver transistor melted down, and under the playfield, the lower diverter coil was totally burnt.

I know about the Williams service bulletin regarding the diverter gate binding, and it was already addressed before I bought the game. I sent the board back to the guy here in MA - a guy who is NO DUMMY; he used to work at MIT - and he seems at a loss to explain what the hell is going on. At this point I'm out yet another $100 for repairs and don't know whether to try to keep the game running or try to sell/trade it. But I'd feel shady selling or trading without full disclosure, at which point it seems like most people would pass.

I'd really like to get to the bottom of this, if only for the peace of mind.

Coil. Diverter COIL. Proofreading...

This was the email from Coin-Op Cauldron, the first time I had trouble:

"Hi Benjamin

Your boards are now ready and a lengthy repair process and are now 100% functional. The board was originally from a Jokerz! pinbal machine and had a unique noise modification from the game installed on the rear of the board which was removed during repair.

It is important to find the switch shorted to the lower divertor coil and check that the coil itself is still good and not fried prior to reinstalling the repaired CPU board as the board will be damaged again.

Work performed (all new parts):

Williams C-9939 Flipper board (SN 554 105432): Replaced F2 fuse (4 amp slow blow fuse -- 5 amp installed). Replaced dried-out capacitor at R4 -- 100uf/250v radial. Reflowed solder for all headers, and all components on board (fixed numerous cracked solder joints):

Williams System 11B CPU (SN 563 241080, F-14. Blown logic with prior repairs): All socketed ICs removed and tested. ROMs (4) removed and internal data verified (Vcc +/- 0.25v). U26 and U27 game ROMs upgraded to version 1.0 software (NOS 27C128 and 27C256 EPROMs). Removed Jokerz! sound modification and restored cut trace. Removed blown ICs and burning/carbon scoring from U45 and U50 areas. Zero ohm resistor (W7 -- cut). 7407 IC and 14-pin socket (U49). 2x 74F02 ICs (U45, U50) and 2x 14-pin IC socket. 2x 6821 PIA ICs (U10, U41) and 2x 40-pin IC sockets. 6821 PIA (U54). 7406 IC (U56) and 14-pin IC socket. 4x 6.8 volt zener diodes (ZR3, ZR4, ZR5 and ZR7 -- all shorted). All transistors checked, -- 2x 2n4401 transistors (Q68, Q78). 2x TIP122 transistors (Q69, Q79). Reworked prior repairs to Q6 area, -- new TIP102 (Q6) and 2n4401 (Q2) transistors. Removed flux from prior repairs. Replaced out-of-tolerance capacitors; -- 2x 10uf/35v (C8, C15), 22uf/16v (C30) and 3x 100uf/50v/105c (C24, C26, C29). Various areas around board had solder reflowed. Added 3AA remote battery pack system. Board cleaned-up."

This is an email from the *current* repair job. My replies follow.

"Hi Benjamin,

I repaired your F-14 board. The damage was further than usual. The cause appears to be different from what I had guessed earlier. ZR8 failed short, which caused switch triggered solenoid 5 (Q77, upper diverter) to lock on. It also caused U50 to fail, which locked on switch triggered solenoid 6 (Q79, lower diverter) to lock on. This caused the melting of the coil and the failure of Q79. This leaves me with a few questions:

1. Are there any wires connected at 1J18-8 and / or 1J18-9? The manual shows them but it doesn't make sense, because the diverters are only controlled by the computer, never directly by a switch like the slings and pop bumper are.

2. What number coil are you using for the lower diverter? They should both be 26-1500. This is a weaker coil which can be energized for a few seconds. If you watch the diverters during game play you can see that they hold for a while. If you have a 23-800 or something, it's going to fail pretty quickly.

3. Have you checked the switches on the left and right center ejects? They tell the computer to de-energize the diverter coils. If the switch is bad, the computer will time out and de-energize the coil, but it would be energized for longer than normal."

"1) There are wires at the connectors on the board end at IJ18-8 and IJ18-9, but they end at the molex connector (that is to say the molex to the backbox has them, but not the molex to the playfield. Weird.)
In fact, there are 7 wires coming off the board at that location, but only 3, 4, 5, and 7 continue to the play field. (Orange/Red, Orange/Yellow, Orange/Brown, White)

2) Both coils are 26-1500

3) I did a continuity check on the center eject switches, and I do get a beep when I close it. I haven’t tested it with a ball, but at no point have I noticed a problem with the ball not kicking out right away."

Reply from board repair guy:

"ZR8 is a Zener diode. It's a low-tech voltage clamping device tied to each trigger line. It is supposed to protect the board from external voltage spikes. It failed short, which simulated a closed input switch to the upper diverter. Of course, the diverters are only controlled by the mpu, there are no switches. But the circuitry is still there. That's why the orange wires (except the three for the two slings and one pop) stop at the playfield connector block. It seems like a voltage spike traveled up the wires and zapped ZR8. Or ZR8 got whacked by space particles and just decided to fold. It's hard to know for sure."

Bump.

Help a brother out! Bump.