So I have a fairly rough original Black Knight machine bought a few years ago that originally had plenty of issues, many of which I have managed to resolve. I had pretty weak flippers and replaced the mechanical portion (piston/lever arm/spring) of both lower playfield flippers with a newer and more reliable style (the type with the long, narrow tension spring holding the flipper in it's rest position rather than the large conical compression spring). The left side now works fine, but the right side is pathetic. It activates but very weakly, buzzing and struggling all the way. Here's what I can tell you:

The mechanism moves freely when I manually cycle it from beneath the table with no binding or unusual resistance compared to the good flipper on the other side

Voltage is about 37 volts at the leaf switch (I have cleaned with paper and get a good spark when I slowly close the switch wit the flipper button)

When I have the playfield tilted up on the prop rod, the flipper seems to be as quick and snappy as it should be, but as soon as I lower the playfield down again it is once again hopelessly weak. To me it seems like this must be some kind of mechanical binding, but honestly I can't feel any unusual resistance when I cycle it manually. Any suggestions on what I should check next?

Thanks!

Grinch

Thank you mikat11, I will go and check that now.

Just looked. The EOS switch is new and makes good contact (closed when flipper at rest) even when the field is lowered. I put a jumper across just in case and tested it, no improvement. Next thought?

Thank you Black Knight. To address your questions:

Yes, I replaced the playfield bushing.

Yes, I gapped the flipper from the playfield properly.

No binding of the rubber on the inlane guide.

New coil sleeve.

*I will check the voltage at the coil and see if it differs from the switch

*There is some obviously molested wiring on the coil, I will check and see if it is correct.

So the wiring looks correct, and I get 24 volts at the coil for both the normal left flipper and the droopy right flipper.

I feel like it ought to be a mechanical rather than an electrical issue, because when I activate the flipper when the playfield is propped up it seems to work fine. That's what really has me puzzled.

Update: SOLVED

Turns out it was in fact a mechanical issue. Although I had gapped the flipper to spec something came loose and there was too much play between the flipper shaft and the playfield bushing, causing the piston to bind against the coil mounting bracket. I pulled the whole thing out and disassembled/reassembled it, gapped it again, and snugged the retaining nut tighter. Bingo! I can play again!

Thanks for your input everyone, sorry for being a noob. I'm learning : )