Hi all. I would certainly appreciate some help here.

After moving to a new location, I noticed my JD UR flipper had become weak and was behaving oddly. All other flippers seem fine.
In game, the UR flipper bat would sometimes feebly attempt to flip up but would end up wobbling in the middle, never making a full flip, sometimes it would make a full flip, but it was just very weak, and sometimes it would only be a little weaker than normal.

What I've ruled out so far:

• Not mechanical. Replaced coil sleeve, bushing, end stop and solenoid slug with new ones. Issue remains.
• Flipper test mode works fine. Power coil flips the flipper at full strength (stronger than in game). Hold coil pulls flipper up when manually moved about half way up, and at holds at end of stroke.
• Flipper EOS switch seems fine in switch test. Activates when flipper bat manually moved to end stop.
• Flipper button opto board seems fine in switch test. Both switches activate as they should.

After rebuild of the flipper, I noticed the coil was audibly buzzing when the flipper button was held. The coil seemed warmer than any of the others. I measured 30vdc on the coil's power winding between blu-yel / blk-yel, when held at EOS. As far as I can tell, this is a problem!

Measuring the power coil of the UL flipper (gry-yel / blk-blu), I was getting less than 1vdc when held at EOS. I noticed if the flipper button is held for about 5+ seconds, the power to the flipper is cut and the buzzing stops. I think this is a fliptronic feature to avoid coil burnout in cases like this. So it seems the power coil is not being turned off and switched to the hold coil when the flipper hits EOS.

From reading this archived thread I found, the last post seems to indicate that one (or perhaps two) of the TIP-102 transistors on the fliptronic board may be at fault and needs replacing.

It's worth mentioning, that while I was working under the playfield recently, I ended up causing a ground short while the machine was off (residual charge in the flipper circuit to switch matrix I think), which showed 4 of the switch rows shorted to ground. I resolved this by replacing the LM339's on one of the playfield opto boards, and the trough board. This flipper issue is the only issue I'm currently experiencing on the game.

Questions:

1. Which TIP-102's are responsible for the UR flipper operation. _{Answered below}
2. Could any of the 2N5401 transistors also be to blame?
3. I noticed another two LM339's on the fliptronic board. Could these have also been affected when the other opto ones fried?
4. How do I measure voltages properly at the coil? Did I measure the UR coil correctly? Is the only option measuring the two coil lugs when the flipper is active, or can you measure one lug to another ground point somewhere when it's not active?

Any further advice would be greatly appreciated.

Found a schematic online.

UR Flipper transistors & comparator

• TIP-102:
• Power - Q8
• Hold - Q7
• 2N5401:
• Power - Q16
• Hold - Q15
• TIP-36C:
• Q2
• LM339:
• U6

I'll be replacing Q8,7,16,15 unless anyone has any other ideas?

Well, I wouldn't have believed if I hadn't seen it with my own eyes.
I gave the flipper button opto board a good cleaning, and the problem is now solved! Gave it a good few days of play before I was truly satisfied that the issue was truly fixed

It's so strange how the buttons reported correctly in test mode. I've now heard from other sources of a 3rd 'half-state' that optos can sometimes be in when they get dirty, where they work in test mode, but in game, they behave erratically.

Thanks for the suggestions and assistance everyone!

Sounds like that would have been something easy to eliminate with a little sanity-check in the game logic code.