BK80: Flipper Flutter

[lothian]

Black Knight 1980

The right lower-playfield flipper on my BK80 flutters when both upper and lower playfield flippers are "up". Flutter does not occur when I close the lower-playfield flipper contact or when I close the upper-playfield flipper contact—lower-playfield flipper flutters only 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; I replaced the EOS switch and set its gap perfectly; and I cleaned the flipper button leaf switches—the flutter persists, and so I post here for suggestions.

 

[luch]

had same problem on mine , i changed the coil

 

[sylvain]

As Luch stated, this is typically an issue with the low-power hold coil wiring (opened) on that fluttering flipper.

Did the issue just start, or you recently purchased the machine with this issue already present?

If you are absolutely certain that the lower right flipper coil is good:
- Is it the proper original flipper coil number, or did someone replace it by a non-original/wrong coil in the past?
- Does the right Magna-Save work fine or not?
If it works fine, it would probably confirm the power supply rail/connectors wiring (flipper B+) to the flipper are good, according to the schematics
- I would also look at all connectors in-series to the flipper, starting at Z1 relay/solder joints on the Solenoid Driver, then through connectors 8P6/8J6, 8P3/8J3, and 7J1/7P1, in case there is high-resistance in one of them causing a voltage/current drop enough to cause the lower right flipper low voltage causing flutter when both right flippers are activated.

Good luck!

 

[lothian]

1) I removed the coil on the fluttering flipper (right) and checked its resistance with a DMM—it tests OK.

2) I removed the left coil where there is no flutter and wired it into place of the right. Result: The (right) flipper with the left coil flutters. I wired the right coil in place of the left—the (left) flipper with the right coil does not flutter. This tells me the coil is not the problem.

BK80 has pairs of flippers serving lower and upper playfields that actuate simultaneously with left/right buttons respectively. The flipper button leaf switch has two contacts: one contact each for lower and upper flipper coils,

3) Flutter does not occur when I close the right lower-playfield flipper contact; flutter does not occur when I close the right upper-playfield flipper contact. The right lower-playfield flipper flutters only when I close both upper and lower contacts simultaneously. This tells me the coil is not the problem; and, the leaf switch is not the problem.

I think the suggestion to t'shoot at the driver board is a good one. That's where I'm headed next.

 

[sylvain]

New more recent details on pinside?

BK80: Hunting the Cause of Flipper Flutter | Tech: Early solid state | Pinside.com

| Forum Topic by lothian

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[lothian]

I think I fixed the flutter. The EOS leaf was making contact with uninsulated bit of the crank tang. I repositioned the EOS so that it was fully within the insulated and flutter disappeared. Makes zero sense to me why this made any difference given that the flipper base plate carries zero voltage and isn't grounded.