F-14 Tomcat 06C flasher and knocker not working

My first post and I am looking for input. I have combed these boards like a parasite for the last month and a half as I brought my F-14 Tomcat back from the dead after being stored for ten years. I’m nearing the finish line with one last issue to resolve, but I am stumped on this one.
Flasher 06C and the knocker don’t work. I realize they are related. I have tested what I could, but have had no luck resolving the issue. Following are the things I have done. (I learned it all from these boards including temporarily replacing fuses with thermal breakers. Thank you.)

All other flashers – and everything else – works
Checked fuses first by removing and checking continuity – all of them
Tested continuity from 06C’s flasher board (blk/blu) to diode board. Good
Tested continuity from diode board (gry/blu) to MPU. Good
Tested Q23 transistor. Good. Common on center leg .582/.507 Common on outer legs null
Q19 reading .2 and change on one side so I replaced it. No improvement
Tested knocker coil and diode. Good (this is a new coil)
Tested flasher board resisters. Good – (resistors are new since old ones were broken)
Verified good soldering – no cracked or loose solder
Started diagnostic and jumped from the ground strap to Q23 tab and knocker fired
Started diagnostic and jumped from the ground strap to Q23 tab and 06C bulbs lit up solid - not flashing
Started diagnostic and jumped ground and driver on the flasher board and again the bulbs lit up solid – not flashing
Disconnected from J11 and J12 on MPU and tested diode on diode board. Good. .5something and null (not sure this was correct procedure)

I’ve considered SR6 or SR7, but I don’t know how to test them and I have no replacements on hand. They seem to serve multiple circuits though so if one were bad I would expect to have more issues. Wiring diagrams and schematics are not my forte, but my eyes are blurry from staring at them in the manual. If anyone has a suggestion as to what the issue might be or where I go next I would appreciate the input. Thanks.

#2 3 years ago

JAM

Jmckune

Pinside member

5y 80,850 1,894 7

Have you checked the pre driver? It seems like your main transistor and wiring are good. Check what should be Q22 it will be much smaller than Q23 but it is apart of that circuit and if bad can prevent grounding

#3 3 years ago

RDN

kcirrick

Pinside member

Thanks for the quick response and suggestion. I'll check it out.

#4 3 years ago

RDN

kcirrick

Pinside member

I guess I'm confused, tired or both. I thought Q19 was the predriver. I checked Q22 anyway and it was good, but I looked at the solenoid table and it shows Q22 to be for flasher 08C. I'd be glad to try any other ideas, but I've got an MRI tomorrow and should get some sleep. Thanks for the input.

#5 3 years ago

FNG

DumbAss

Pinside+ Frequent

9y 109K 2,977

OP
Quoted from kcirrick:
Tested Q23 transistor. Good. Common on center leg .582/.507 Common on outer legs null

A transistor that tests good does not mean it is good. A transistor that tests bad means that it is bad. You may get false positive results. You will not get false negative results. I have a TIP102 transistor that tests good but is internally shorted (solenoid locks on when installed).

OP
Quoted from kcirrick:
Q19 reading .2 and change on one side so I replaced it.

Test this transistor as well. The legs are EBC (TO-92) not BCE (TO-220) so take care with lead placement.

OP
Quoted from kcirrick:
Started diagnostic and jumped from the ground strap to Q23 tab and knocker fired

All this indicates is that your playfield wiring is good. It does not mean the transistor is good. All you are doing is shorting the collector (power supply) to the emitter (ground).

OP
Quoted from kcirrick:
I’ve considered SR6 or SR7, but I don’t know how to test them and I have no replacements on hand. They seem to serve multiple circuits though so if one were bad I would expect to have more issues.

These are resistor networks (or resistor packs). They are pull-up and pull-down resistors. Test the resistance from pin #1 to the appropriate pin.

OP
Quoted from kcirrick:
I guess I'm confused, tired or both. I thought Q19 was the predriver. I checked Q22 anyway and it was good, but I looked at the solenoid table and it shows Q22 to be for flasher 08C.

Correct. Q23 is the drive transistor (TIP122 or TIP102). Q19 is the pre-drive transistor (2N4401).

01_schematic.jpg

If you think the drive and pre-drive transistors are good then you need to go further upstream to the digital logic. You can test all the ancillary support components as they are fairly easy to test. To test digital logic you should get a logic probe.

02_solenoid_table.jpg

#6 3 years ago

RDN

kcirrick

Pinside member

Thanks for all that information. I will go ahead and replace Q23 anyway. I'll retest Q19 and post the values. I'm afraid I have to plead ignorance on "EBC (TO-92) not BCE (TO-220)". I believe my earlier test was with the DMM set on 'diode' and the common on the center leg. I think I have a logic probe out in the workshop although I've never used one before. I'll research the basics and see what I can do with it. I'll go ahead and test the resistor pack as well. I suppose I can just follow the trace to determine which pin to test. Again, more research will be required to find out how to test and what value I'm looking for. I'll post once I get this all done.

#7 3 years ago

BOB

bobukcat

Pinside member

9y 99,550 5,463

OP
Quoted from kcirrick:
Thanks for all that information. I will go ahead and replace Q23 anyway. I'll retest Q19 and post the values. I'm afraid I have to plead ignorance on "EBC (TO-92) not BCE (TO-220)". I believe my earlier test was with the DMM set on 'diode' and the common on the center leg. I think I have a logic probe out in the workshop although I've never used one before. I'll research the basics and see what I can do with it. I'll go ahead and test the resistor pack as well. I suppose I can just follow the trace to determine which pin to test. Again, more research will be required to find out how to test and what value I'm looking for. I'll post once I get this all done.

B=Base, in simple terms this is the control input that turns the transistor on or off. C = Collector, the top connection shown in the schematics. E = emitter, the connection on the bottom of the schematic drawings. TO-92 and TO-220 are the package types, or basically what size and shape the transistors are and as stated looking at the front of them EBC and BCE are the respective pin-outs of the two transistors in question. Since both transistors in question are NPN the proper test would be (in diode test mode) red on the base and black on the emitter. A good transistor should test about .7V drop and should be open in the opposite direction.

#8 3 years ago

RDN

kcirrick

Pinside member

Solved!

I read your explanation six times and kind of got the gist of it. I didn’t find the logic probe so I continued to experiment with the DMM. I was going through testing stuff and for some reason started testing SR6. ( I believe the comment was, "go further upstream".) I noticed that pin 7 had continuity to ground. That didn’t seem right. I checked SR4 and pin 7 did not have continuity to ground. I followed the SR6 pin 7 trace to U19 and had ground on that pin too of course. Pin 1 on U19 does go to ground. I could see no reason why this other pin (11? I don’t know the pin order on this chip) should be grounded. U17, U18 and U20 didn’t do this. I took a chance and replaced U19 thinking it might be shorted inside. After the replacement, only pin 1 on U19 had continuity to ground. I felt this was promising. I reinstalled the board, powered up the machine, held my breath and went to the diagnostics. When I got to the knocker it started firing as it is supposed to. Next were the 06C flashers and they were flashing as they were supposed to. It all works!

My methods may be unorthodox, but they eventually worked. I can’t thank those members enough that responded to my plea for their quick responses and for giving me direction. I will certainly try to return the favor should I see an issue posted that I had to deal with.

Now I can focus on finishing up the rest of my game room.

Post last edited 3 years ago: “punctuation”

#9 3 years ago

???

BobbyAtk

Inactive member

Glad you found the bad gate (U19). I've got a F-14 as well. Mine's chief quirk is if the flippers are hit before the ball is put into play, the player up is often (but not every flipper activation) awarded 1,000 points. I'm thinking the flipper is either generating a spike that it being seen as a switch high, or dropping the voltage enough it's seen as a switch going low. Haven't dug into it yet.
Congrats on resolving your issues, it's a fun game.

#10 3 years ago

BOB

bobukcat

Pinside member

9y 99,550 5,463

Quoted from BobbyAtk:
Glad you found the bad gate (U19). I've got a F-14 as well. Mine's chief quirk is if the flippers are hit before the ball is put into play, the player up is often (but not every flipper activation) awarded 1,000 points. I'm thinking the flipper is either generating a spike that it being seen as a switch high, or dropping the voltage enough it's seen as a switch going low. Haven't dug into it yet.
Congrats on resolving your issues, it's a fun game.

That type of behavior is usually mechanical, not electrical. Put the game in switch edge test and bang on the playfield with the palm of your hand and you'll likely see a switch activating.

#11 3 years ago

???

BobbyAtk

Inactive member

bobukcat Good call, the upper loop switch was causing the 1,000 point problem. Thank you.

P.S. I foolishly played with the diagnostics a little while there, now I know that flashers 1,5,7, and 8 aren't working. LOL

#12 3 years ago

???

BobbyAtk

Inactive member

Curiously I tracked the missing flashers mentioned above to the cause. Several of the 5 ohm 10W resistors used on the small 5/330 (7W) ohm divider boards have been removed leaving the 5 ohm part of the circuit open. Does anyone know why this would have been done ? They aren't failed open resistors, they have been physically removed. If these flashers were distracting, it would seem much easier to just remove bulbs. Does anyone know why this would have been done ?

#13 3 years ago

BOB

bobukcat

Pinside member

9y 99,550 5,463

Quoted from BobbyAtk:
Curiously I tracked the missing flashers mentioned above to the cause. Several of the 5 ohm 10W resistors used on the small 5/330 (7W) ohm divider boards have been removed leaving the 5 ohm part of the circuit open. Does anyone know why this would have been done ? They aren't failed open resistors, they have been physically removed. If these flashers were distracting, it would seem much easier to just remove bulbs. Does anyone know why this would have been done ?

So they could use LED flashers and blind the player even more severely than the #89s that were factory!!

#14 3 years ago

???

BobbyAtk

Inactive member