[R-390] COSMOS PTO ..E.Point and LInearity

[Pete Williams]

​  My take...  having done about 20+ over the years, I have yet to find one
that has never  been touched internally, let  alone satisfactorily
linearised or  end pointed . There's  always someone that has been there
before me , compounded by drift in capacitor value changes to permeability
of the  core or  a  combination.
The  end point adjustment usually gets the  advice to remove a turn from
the   end point coil.
I can't  recall  an instance  where this proved  to solve the  problem and
always ran out of slug on the  EP  coil when going through the procedure
Like I said, others have  been that way without success, and I don't
tolerate  a few kHz out at the  ends
At the risk of  raising eyebrows, what I have done for remedy is  as
follows ..
1.. disassemble  and  remove the  EP  coil.

2.. rewind with equivalent gauge  wire  and  put on 3 turns - seal with
nail polish.

3..remove the  10pf NPO capacitor....

4. return the  slug in the  EP coil to full in position. ACW.
Lower value  capacitors have been tried  but  eliminating 10 pf  works for
me ..
I power  the    PTO being worked over from a dual voltage ,adjustable  and
regulated power  supply with pto output  to a  counter.
The EP  and  linearizing procedure  is then done per previously recorded
info on this list  and  ER  articles.
No major change in stability with temperature ..cold  start to heating to
too hot  to hold  no worse than about  50 Hz  at 3.455Mhz.
Maybe others have  done  something  similar, but I've not read of it..
Cheers
Pete VK3IZ



.