Thank you Sir!

Wow, what a fix! Great post with great pictures.

Could you please list the effects of the failure if this fix is not done?

Flippers just stop working?

Thanks again for your time!

Will your fix work with TFTC as well? Do you know if the trace needs to be cut? Thanks this issue is driving me nuts I think this is the answer

Got it thanks - and you also did the Capacitor on bottom of board and jumper R23 correct just not pictured? I guess what I wanted to make sure is if you followed the Service Bulletin exact with the exception of what you called out.

I appreciate your assistance. While I wait on parts I wanted to do the test mentioned in the service bulletin.

It says to attach a jumper wire across the EOS switch lugs. Do I have this right in picture? Just jumper on of the back blades to the other? Thanks again

3FD870B1-B977-43B6-9374-8373F12E9ACF (resized).jpeg

Thanks the test verified this is my issue.

Just found this thread reading the the LAH thread. I'm trying to read as much as I can before I ask questions. I have an issue where every now and then the right flipper doesn't work. I have something else to test but this may just be my answer. Thanks.

i have a Data East Jurassic Park and the left flipper and right upper work perfect everytime but the right lower will work sometimes and then others it wont go up. if you help it up it will hold . when it doesnt work, you can hear a hum and feel it humming. new EOS switch, new cabinet switch, new coil, wired correctly. no blown fuses. drives me insane. i figure it's the flipper board, maybe a bad transistor.

There are a couple of Jurassic Park flipper threads out there.

I just commented on this one:

https://pinside.com/pinball/forum/topic/data-east-jurassic-park-right-lower-flipper-not-working

Start by taking an alligator clip and jumpering across the End of Stroke Switch of the intermittent flipper.

This isn't a permanent fix! It's just for troubleshooting. If you now have good power reliably on that flipper, you know that the End of Stroke switch or possibly the TYFFASI board is the problem.

And since you are posting on the Flipper board thread, what is the part number of your flipper board, has it had the updates applied to it that are recommended by Stern and documented in this thread, and have the fuse clips on the flipper board been replaced?

Jumpering the EOS an easy test, so jumper across the End of Stroke switch and let us know what you find!

Just did this mod to my 520-5070-00 LAH flipper board. Even with brand new EOS switches that were clean and tight, I was still having non-responsive flippers and flippers dropping out.

The above diagrams were helpful getting R23 pulled and the diode/resistors installed. I ended up installing the components on the solder side of the board for a cleaner look. I wrapped the components in shrink tubing before installing.

It wasn't really clear reading the above where the two 1uFd capacitors go. But, one capacitor goes to CN1-1(+)/CN1-7(-) and the other goes to CN1-9(+)/CN1-10(-) on this particular board.