[BC] FM10K

[richardbrianjohnson at verizon.net]

 A common problem with tetrodes and equipment that is "incompletely designed," is that vacuum tubes sometimes arc from plate to screen. Early designs had arc-gaps across screen bypass capacitors to handle these infrequent events. Apparently "manufacturing engineering" at various companies decided they were not necessary and eliminated them. Also, equipment that still retains them often have them bent away by so-called broadcast engineers because they arc! They are supposed to arc so you don't need to change a socket because its built-in screen bypass capacitors have been been destroyed.
 
The same kinds of problems problems occur with ceramic insulators. Correctly-designed equipment that has high RF potentials on ceramic insulators have metallic end-caps on the insulators so that RF currents flow through the ceramic and not the tiny air-gap between the screw and the insulator. When manufacturing engineering removes these end-caps from the designs, claiming that they are not necessary, the result is that insulators crack and screws get spewed out.

Most all vacuum-tube transmitters by any/all companies, including the ones for whom I worked, were copied from existing designs with improvements made as new tubes and components became available. However, many of these copies by low-level competitors had basic physics, electrostatics, and mathematics ignored. Eventually there were no competitors and the copies seem to be copies of the worst designs imaginable. That's what you've got left -- the bottom feeders.

 Cheers,
Richard B. Johnson
http://www.AbominableFirebug.com
 
On 11/11/13, Bob Groome<bobgroome at gmail.com> wrote:
 
One more thought; in the FM-10H and FM-10H, the PA tube socket was modified at the factory, may be the same in the 'K'. If so, check the factory to see what they did. Fred Anderson