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(Solved)F-14 tomcat. Right sling locks on at power up

Luckydogg420

Member
May 12, 2013
825
24
18
Kitchener
This is a special solenoid I think, and I've checked the coil circuit. While I was looking for the problem I found a previous owner changed the coil power on the 2 upper left diverters to 70v, instead of the 34v it's supposed to have. Because of this there was transistors that had cold solder joints. I replaced the 5 special solenoid transistors to be safe.

I thought the problem was originally with the coil power because if I remove wire 4 from connector 1j19 the right sling coil will disengage.

But now in thinking the problem might be switch logic, but a problem could be in the playfield wires.

Just wondering if I'm over thinkin this. I don't have any switches registering on the switch edge test. Could it simply be a bad diode?
 

sylvain

Active Member
Apr 27, 2013
209
75
28
Ottawa, ON
Re: F-14 tomcat. Right sling locks on at power up

1- make sure the right sling coil has its diode in place across the lugs, and is properly soldered.
A missing or opened diode there would cause the Q71 TIP122 transistor to short after the 1st impulse.
(if the diode was backwards or short-circuit, the Q71 transistor would blow (and the solenoid fuse)
and the sling would not even operate).

2- check transistor Q71 for short circuits between pins. Replace if shorted.

3- Make sure the right sling switch is not shorted or incorrectly adjusted with its backing plate shorting the contact stack.

4- Remove the small 2N4401 transistor Q70. Is the coil still locked on ?
If no, problem is with that small transistor or upstream (U45, a 7402 TTL chip) or around this portion of circuit
(SR20-6,ZR6,R100,R101,C73);
If yes, then there is an issue with Q71 again or its soldering on the board.

Good luck !
- Sylvain.
 

Luckydogg420

Member
May 12, 2013
825
24
18
Kitchener
Re: F-14 tomcat. Right sling locks on at power up

The Q71 was changed when I noticed the diverter hack. During game play the ball diverters work fine, although their logic seems messed up. The game will send the ball to the wrong place occasionally while locking for multiball. I'm going to assume the previous owner thought this was a power problem, so that's why they hacked the power. Taking 70v instead of 34v. Since returning it to the right wire they work, except for logic

I changed the diode on the coil, no luck.

There's no continuity thru the sling switch when it is open and power is off. They also visually look ok. If I tap on the switch while probing the lugs it reads continuity.

Probing the transistors for continuity tests ok, there's no shorts between the three legs on Q71 or Q70.

I think the problem is with the 7402 chip because there's logic issues on other coils that it controls. I have parts so I will remove Q70 and see if the sling still locks on. If that's not it I will replace the 7402 Chip.

Just wanted to make sure I covered all bases
 

Luckydogg420

Member
May 12, 2013
825
24
18
Kitchener
(solved) F-14 tomcat. Right sling locks on at power up

I snipped transistor Q70 off the board. Turned it on, coil didn't engage. Installed a new Q70, back on, coil locks on...crap.

Removed the logic chip up stream (U45, 7402 chip) installed a new one. Machine on again and the coil is fine.

Played a game and the right sling works fine.

Thanks for the help.