(Topic ID: 337202)

Help... Space Jam sticking flipper I cannot figure out.

By dem_bones

10 months ago



Topic Stats

  • 4 posts
  • 2 Pinsiders participating
  • Latest reply 9 months ago by dem_bones
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#1 10 months ago

Hi All,

I have a problem I thought I could sort out but cannot solve.

I have a Space Jam machine whose right flipper is locking on, blowing the 3A fuse, and blowing the Q16 transistor when I hit the flipper button. It is not locking on when the machine initially powers up or a game is started - only when I hit the right flipper button. The problem is not mechanical - the flipper unlocks when the power is turned off.

I have done the following:
Replaced the coil with 090-5020-20T (comes with a new diode). Made sure that the diode's polarity was the same as the old coil.
I have replaced the Q16 transistor with an IRL540N
I have socketed and replaced the U2 IC with a 74HCT273N

Some other clues:
The coil was hot when the fuse first blew and we initially discovered the problem.
The diode on the old flipper coil seemed to test ok.

I don't quite understand the end of stroke switch on these machines. I tested it for continuity. When the flipper is down there is continuity where the wires connect at the base of the switch and when it opens there is not.

For context:
I do not have a deep understanding of electronics, but have been able to sort out most problems with my machines over the years (thanks to threads here!). I have multimeters, good desoldering and soldering tools.

Any advice or suggestions of how to test and track down the issue would be great.

#2 10 months ago

You've done the good work here.

Overwhelmingly, when I have a problem with weak or locked on flippers on Whitestar CPUs, it's prior work replacing Q16 with something other than a IRL540N. You've already worked this problem.

In general, yes, End of Stroke switches are troublesome, but on this generation even with the End of Stroke being absent the CPU should be reducing power to the flipper after a tenth of a second or so.

IRL540N transistors are TOUGH! It takes a fairly direct short to pop them.

So.

Measure the coil resistance, technically it should be 3.4 ohms, less than two ohms the coil is now bad, and needs replacement.

Banded side of the diode goes to blue-yellow wire.

Replace the IRL540N again. Mosfets are hard to test, and if this mosfet is compromised, it's easiest to test by substitution.

I have a 2 1/5 amp circuit breaker that is soldered to a blown fuse. The fuse next to the flipper, I do my testing with a circuit breaker, or fast blow fuses, frequently I'll use a 2 amp in the place of a 3 amp fuse and / or fast blow. I want the fuse to protect the circuit as I plug things in!

I'm thinking this... In order to pop the 3 Amp flipper protection fuse the coil has to stay full power (not reduce the voltage to a 'hold voltage' state) for a fair amount of time, or the coil resistance needs to be less than 2 ohms, or the flipper diode doesn't have it's banded side to the blue-yellow wire.

To take the End of Stroke switch out of the equation, I use an alligator clip to short the wires going to the EOS switch together. This probably won't be helpful, I don't think the game will attempt to re-apply full power to the coil over and over even if the contacts of the EOS are bouncing.

Let us know what you find... this is presenting as 'impossible' problem, and when I have those, I have to re-examine each step in my troubleshooting carefully. You've already done these steps, but abandon your memory, and go through the basics again.

Good luck!

#3 10 months ago

Awesome. Thank you for the advice. I will try all of this and report back. I appreciate you taking the time to chime in.

2 weeks later
#4 9 months ago

I finally got some time to spend on this (work and life have been hectic). It's still not fixed but I have some new clues. I tested the new coil (and old coil) they tested fine. Diode is wired correctly. I did a logic test with J9 unplugged. At U2 pin 19 power is low when the flipper button is not pressed and low/high when the flipper is pressed in. It turns off and on with the flipper button. This is exactly the same behavior as u2 pin 16 when pressing the left flipper (which is working correctly). New development tonight is this. When we plugged J9 back in and turned on the machine the right flipper did not power up or stick... But when we started a game and the ball ejected - the right flipper locked on again, WITHOUT hitting the flipper button. I initially though the problem was caused by hitting the flipper button, but not this time. Does this tell me something new? A short somewhere?

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