[R-390] More PTO questions

[n4buq at knology.net]

Still poking around in this PTO.  Were some PTOs manufactured without 
linearity adjustments?  I seem to recall some discussion a few years ago 
that some did not have them.  This one doesn't have an access hole for any 
adjustments.  The large hex bolt plug on the "right" exposes only the 
endpoint adjustment.

Also, there is another hex "bolt" on the "left" made of the same material 
as the bulkhead (bakelite perhaps?) that has "S701" labelled beside it.  It 
exposes a hollow shaft with a slot that is assumable for a screwdriver.  Is 
this a way to disable the heater thermostat?  A reset for it, perhaps?  I 
haven't seen it discussed anywhere or mentioned in any of the manuals.

Regards,

Barry - N4BUQ