Hey all,

I'm trying to troubleshoot a new issue on my Big Guns. The UR flipper has become very weak. It powers up with some modicum of strength, but it eventually becomes so weak that the flipper doesn't even fully flip. You can also hear a buzz/hum when this happens. See this video for an example:
https://photos.app.goo.gl/WmnwnGFVSkNpMnBL6

What I've tested thus far:
- The EOS switch seems to be adjusted fine - see photos for details. Contacts are made/unmade when appropriate.
- There is no resistance when manually plunging the crank assembly and I rebuilt the flipper (new crank assembly, coil sleeve and stop) a year ago. The game gets only a few plays a day. This leads me to believe it is not a mechanical issue.
- Voltages are suspicious on the left lug of the coil when engaged. Normal (open circuit) voltage is 71.6-71.91v, but closed it is coming in at 0.16-0.18v. This definitely seems out of line compared to the other flippers.

I'm curious if this might be a faulty diode or capacitor? Any ideas on what to try next?

IMG_20200515_192936 (resized).jpg

IMG_20200515_192950 (resized).jpg

Thanks for the tip. I took a high grit sandpaper (400 or so) to the EOS switch contacts as well as the contacts on the flipper button itself. They're clean, flat and shiny as far as I can tell. The tension on the EOS seems right - definitely a bit of tension keeping the contacts together. The EOS switch tension seems identical to the other flippers too. I'm feeling like its not the switch.

Thinking it could be one of the diodes, I tried the test suggested here. I'm getting 10 ohm across the 2nd (right) diode and 168 ohm across the 1st one. If I'm tracking on this properly, those readings are in line and the diodes should be good.

So what the heck is going on here??! Given that the performance is weak from power-on but gets weaker the more it fires/longer the game is on - is this symptomatic of a different cause? Again, no resistance on the crank assembly, even when the flipper is at its weakest. I don't think this is a mechanical issue.

Could it be the driver board? If so, wouldn't that be causing issues with the LR flipper too? Its strength is solid, no issues at all.

Thanks for the tip. I took a 150 grit sandpaper to the contacts. Now I'm getting 0.23 ohm across the UR EOS switch, but I had to press the contacts together to get a good reading (that wasn't reading as if the switch was open). So clearly, the switch needs to be replaced. Good call.

I've ordered some new caps and found some new EOS switches laying around (they were in my original rebuild kit and I shamefully never installed them - lesson learned!).

Sidenote: The resistance across the other EOS switches is above 1 ohm and I'm seeing oxidation I didn't notice before. So all 4 of them (+caps) are getting a proper replacement once the parts come!

I'll update here when done, but I'm feeling good this should do the trick. Thanks again, @phishrace.

I finally finished replacing the EOS switch on the UR flipper as well as the capacitor. I took my new contact burnisher to the cabinet flipper switch as well.

Still no dice.

My friend recommended I replace the cabinet flipper switch, so I'll be doing that next - replace both of them while I'm at it.

Let see if this does the trick...

So I replaced the right cabinet switch and adjusted it. I took my new contact burnisher to both contacts, making sure that they were nice and clean, even though they were brand new. I'm seeing the exact same behavior as before. The LR flipper is strong, the UR flipper is weak.

The only thing I didn't replace was the 0.1uF disc capacitors attached to the switch (these things). I just wired the old ones to the new switch. Could those possibly be the culprit? I'm wondering if possibly this is an issue with the 50VDC coming from the Aux Power Driver board at 5J12. Is that possible?

Any other suggestions here, folks? I feel like I've tried nearly everything I can think of/we've discussed here thus far.

A late update here to close the loop for future problem-solvers and those who might be curious...

In a last ditch attempt, I swapped out the coil FL-11753 since the coil sleeve was locked inside and there was evidence of swelling. And that still didn't do it!

I was ready to throw in the towel completely and then noticed that I had a spare crank link assembly in my supply box and swapped it out on a whim.

And when I powered it up...EUREKA! I couldn't believe it. The flipper was just as snappy as ever.

Apparently, I was dealing with a coil that needed replacement AND somehow had a bad linkage. The latter was only a year old, but perhaps was manufactured with some sort of barely perceptible defect? Hard to know. I purchased it from PL and this was the first time I've ever had something like this happen with a part from them.

Whatever the case, I'm happy to report that the game is playing great again and has provided my family and I many hours of outrageous fun!