Stern Big Game - F4 Fuse Problems

moloch

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I have a Stern Big Game wide body pin and the F4 "7amp slow blow" fuse keeps blowing. I removed the B3 bridge rectifier and I have a 35amp 200v wired in its place.

On the TP5 check point I was getting voltages of 66 vdc.

When I disconnect J3 on the SDU-100 and J4 on the LDA-100 the fuse will not blow.

I do not know a hell of a lot about pinball machines so all of this is new to me.

Which parts of the SDU-100 and LDA-100 should I be looking to replace or check?
 
None of the coils appear to be locking.

If I read the marvin description correctly I set my DMM to Ohm's and test across the contacts. I should have a reading of 2.5 or higher. Any reading lower then that is an indication of a bad coil. This machine has 4 flippers and one of the coils there tests lower then 2.5. If I cut the wires leading to that I hope that I can re-connect everything and not blow a fuse.
 
None of the coils appear to be locking.

If I read the marvin description correctly I set my DMM to Ohm's and test across the contacts. I should have a reading of 2.5 or higher. Any reading lower then that is an indication of a bad coil. This machine has 4 flippers and one of the coils there tests lower then 2.5. If I cut the wires leading to that I hope that I can re-connect everything and not blow a fuse.

Flippers will have 2 windings. It doesn't surprise me that they're reading lower than 2.5 ohms on the stronger winding. Flippers are an exception to the rule but you still don't want to see a dead short and it won't hurt to disconnect the flipper and see what happens.

Are you sure it's J4 you're disconnecting from the solenoid driver board? Not J5 or J2?

EDIT: If it is J4 then I would suspect a problem with the flipper coils, diodes or wiring. J4 carries signals from the MPU including the signal to energize the flipper relay. If you had a problem at the flippers the fuse could blow when the flipper relay energized. I would check the coil diodes. If the problem were a shorted flipper coil I would expect that the fuse would blow when you pressed the flipper button.

J4 also carries other signals for continuous solenoids and data for the decoder that drives the momentary solenoids but I would suspect a flipper problem first assuming that you don't blow the fuse then J4 is disconnected. It's also possible that the enable line to the decoder from the MPU is stuck low. That could cause a coil to lock on but you would probably hear that, the coil would get really hot and it would most likely take a couple of seconds to blow the fuse.
 
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It was told to me prior to you buying this pin, that there was a suspected flipper issue. You should touch base with the person that you got it from. I am pretty sure that he told me the guy he got it from said that there was a flipper issue.

The only reason I mention this, is that it may get you closer to solving your problem.
 
I have been testing the coils and I still only come up with one that is bad. I have desoldered that one.

Out of all of the other coils I am getting readings of 10 ohms on some and 32.7 ohms on some of the others. On the remaining flipper coils I am getting 2.9 ohms between any 2 of the 3 contacts.

Are these readings common?
 
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