[R-390] VFO squirreliness solved FOR GOOD

[DJED1 at aol.com]

Thanks, Tim, for inspiring me to tackle one of my PTOs.  I replaced my  
original Progressitron PTO with a Cosmos because it was warbling as I  tuned.  I 
had cleaned the grounding wiper, and had disassembled the PTO and  cleaned the 
threads, but couldn't solve the problem.  Based on your  comments, I pulled the 
PTO apart, removed the back plate, and removed the slug  and cams (all in one 
piece).  I didn't disassemble the slug, but I was able  to clean and lube the 
entire threaded shaft.  I also resoldered the small  caps as Les had 
suggested.  I put it in the radio tonight, and it tunes  great- no warbles.  The only 
problem I have is that it's off about 2 Kc  end-to-end, and the variation is 
not linear.  I'll tweak the end point and  see how close I can come- it will 
probably meet the original specs when  completed, but won't be as good as a 
tweaked Cosmos.
Speaking of which, I also tweaked the end point on the Cosmos because it  was 
out by 1 Kc.  Fixed that right up, but now intermediate points are out  by as 
much as 1.8 Kc, where they were within 0.4 before I touched it.  And  the 
strange thing is that all the 25Kc points are off the same amount- 1.8  Kc.  All 
the 100 Kc points are right on, and the 75 Kc points are out about  0.8 Kc, 
and also all the same.  Very strange.  I'll look at the data  tomorrow and 
decide if I want to tweak all those little screws, or just put the  end point 
adjustment back to where it was.  
While I was in the radio, I found I had a bunch of BBODs in the IF.  I  
thought I had all Vitamin Q metal caps, but I was mistaken.  I don't have a  full 
set of replacements, but I did replace C553 with an Orange Drop, so at  least 
that is taken care of.
 
Ed