TSPP Flipper always activated. Need some help

mcsdhacker

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Hello everyone,

I have a TSPP and the top right flipper is always engaged, it will run for about 10 seconds and blow the fuse. First thing I did was ohm the coil. I was getting .8 ohms so I replaced the coil but that didn't help, popped another fuse. Ohms on the new coil reads 6.5. So I checked the switch on the cabinet, thought maybe it was stuck closed, nope it was fine. So I checked all connections on the IO board and everything was snug. Last thing I checked was the voltage running through the fuse... It appears there is a constant 160 volts running to the fuse when the interlock switch is engaged. Even when the flipper button isn't pressed. I checked the other flipper coils and there is no constant voltage running through the fuse when the switch isn't engaged, just 50 volts when the button is pressed. I don't know what else to do. Can anyone help?
 
I don;t own a Stern yet, but it sounds like you've got a transistor blown on the board. Look at the manual and it will tell you what transistors drive what. Find the one for that flipper and replace it. If there's a pre driver there replace that also.
 
Thanks for the quick replies. I've gone through the manual and found this transistor which the manual says should be the right one. (Q14) http://www.pinballlife.com/index.php?p=product&id=190&parent=20

Truth is I'm not that familiar with what transistors actually do. Is there a way to test the transistor on the board to verify that is the problem? Is it a matter of testing current or resistance on the drive transistor?

Thanks for your help!
 
Check pin repair, but you test a transistor by putting either the black or red lead on your dmm on the middle leg and then taking the other lead and measuring the outer legs. For a quick and dirty, measure some of the transistors in the row, if that transistors measures differently it's bad.

In this case I would replace it either way. Also, at pin repair they give you detailed instructions and what the readings should be.
 
Yup it was the transistor. Got it put back together and it works perfect. I just have one more to replace and the machine will be 100%. Thanks everyone
 
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