Williams SS Black Knight (Williams, 1980) Flipper Flutter

[lothian]

Black Knight 1980

The right lower-playfield flipper on my BK80 has begun to flutter when both upper and lower flippers are "up". Flutter does not occur when I close the lower-playfield flipper contact or when I close the upper-playfield flipper contact—flutter only occurs when I close both contacts simultaneously.

The most common t'shooting suggestions for "flipper flutter" seems to be 1) cold solder joint on coil lug; a/o 2) problematic coil; a/o 3) EOS switch adjustment. I've investigated each of these suggestions and none appear to be the cause of the flutter. I swapped the left and right coils; replaced the EOS switch and set the gap perfectly; and cleaned the flipper button leaf switches—the flutter persists, and so I post here for suggestions.

 

[pinballdaveh]

Black Knight 1980

The right lower-playfield flipper on my BK80 has begun to flutter when both upper and lower flippers are "up". Flutter does not occur when I close the lower-playfield flipper contact or when I close the upper-playfield flipper contact—flutter only occurs when I close both contacts simultaneously.

The most common t'shooting suggestions for "flipper flutter" seems to be 1) cold solder joint on coil lug; a/o 2) problematic coil; a/o 3) EOS switch adjustment. I've investigated each of these suggestions and none appear to be the cause of the flutter. I swapped the left and right coils; replaced the EOS switch and set the gap perfectly; and cleaned the flipper button leaf switches—the flutter persists, and so I post here for suggestions.

The 2 other things I know of that cause flipper flutter are:
Fiber connecting link gets elongated holes and produces slop when pulling in, and might flutter the EOS switch.
EOS switch wire(s) might have an intermittent crack inside the wire and cause problems. Although a bad EOS wire is rare , it has happened.

 

[lothian]

I think the issue is fixed. I smidgeon of the EOS leaf was making contact with uninsulated bit of the flipper crank lever thingy. I repositioned the EOS so that it was fully within the insulated and flutter disappeared.

The flipper base plate is neither grounded nor tied into a circuit--I don't see why the EOS making incidental contact with it would have any effect. I'm suspicious that I've actually solved the problem.