[R-390] Gear train rebuild help needed......

[Charles Steinmetz]

Bob wrote:

>Phil wrote R-390A.  IF that is the case, there is NO green, Geneva Gear.

More misinformation.  The Geneva Drive used in both the R390 and the 
R390A is not the same as the Green Gear in an R390.  The Green Gear 
is not called a "Geneva Gear."

The Geneva Drive is what has been suggested as a possible problem in 
Phil's radio.  It is shown and discussed on pp. 1-2 of Scott 
Seickel's R390A gear train rebuild tutorial.

The Geneva Drive is a mechanical mechanism that moves a shaft (in 
this case, the bandswitch shaft) in small steps for each rotation of 
the driving shaft (in this case, the MC Change shaft).  The 390 
manual calls it a Geneva mechanism, while the 390A manual calls it an 
"intermittent gear."  Geneva mechanisms typically have a pin that 
engages a slot in the driven wheel. As the drive wheel rotates, the 
pin enters the slot and turns the driven wheel some fraction of its 
rotation.  See <http://en.wikipedia.org/wiki/Geneva_drive>, 
especially the "internal Geneva drive."

The Green Gear in an R390 is a convenience tool that keeps the KC 
Change gear train in alignment with the Veeder-Root counter while you 
have the radio disassembled.

Best regards,

Charles