Originally Posted by
L98FIERO
No one replied so......
It turns out the way to clear this is to turn the rotary switch on the top left of the MD20/MB21 main board to 1, it normally is at 0. I did it with the machine turned off, don't know if it was required but nothing else happened except the machine is then locked out. At that point i could reset parameter 6219 to 1/write enable and change parameter 6014 D6 from 1 back to 0, turn machine off, reset rotary switch to 0 position and was back in business.
Hopefully this helps someone on these old, orphan controls in the future.
BTW, I can't take the credit for this, I had lots of help from my regular non-OEM serviceman, a very smart guy.