[ARC5] BC-221-D, tool needed to undo knobs

[Leslie Smith]

Hello all,

I wish to remove the F.P. knobs from a BC-221-D.  
This is an early model with 5 and 7 pin type tubes.

I have tried 1/16, 5/64, 3/32 Bristol wrenches.  (Allen keys).
I have tried (the most unlikely) metric Bristol wrenches.

I now suspect the correct tool has some type of spline.

Any information welcome!
Help!


   73 de Les Smith
   vk2bcu at operamail.com