[R-390] R390A VFO backlash problem,

[Roger Gates]

Well guys, the problem has been resolved. Like Craig suggested the 
linearizing mechanism might cause the backlash issue, but mine was in fine 
shape and no sign of it causing the problem.

I recleaned the leadscrew and relubed it with Mobil 1/WS2, also placing a 
drop of oil on the rear bearing. I then removed the circlip on the front 
bearing (hoping to remove the bearing), but had to be content with wicking 
some oil into the shaft and bearing. I wonder how this bearing comes out?? 
After working the tuning shaft a bit it seemed to loosen up and quit acting 
as if it had a mind of it's own. I could not detect any backlash tuning it 
against a signal from the 8640B and monitoring the signals in another 
receiver.

The end point adjustment is tedious at best and downright maddening at 
times. After much back and forth, I finally got the 10 turn spread down to 
1.00mHz + about 100Hz. Good enough for me!!

I hope this info helps someone else with the backlash problem. By the way, 
does anyone know of an exploded view of the Collins PTO??

Merry Christmas and Happy New Year to you all.

Roger, W7KVT
----- Original Message ----- 
From: "Roger Ruszkowski" <flowertime01 at wmconnect.com>
To: <r-390 at mailman.qth.net>
Sent: Wednesday, December 24, 2014 1:14 PM
Subject: [R-390] R390A VFO backlash problem,


>
> Fellows,
> I was asked this question and I do not know how to cure the back lash 
> problem in these VFOs. May we have some help please?
>
> Roger, You are going about the end point adjustment the right way. It 
> takes time
> and is boring. Tweak it a big bit to get closer faster. You may find 
> starting from the other end helps you get the adjustment done.
>
> Hi Roger,
> I hope you can shed some light on this PTO problem. I'm asking you because
> you seem to have had more experience than anyone else on the 390 list.
> I have a Collins type PTO manufactured by Progressitron Corp. for 
> Capehart.
> The PTO seems to have some backlash. If I set it for zero beat, it will 
> jump
> back about 300Hz when I let go of the knob or shaft (with PTO removed). I
> have cleaned and lubricated the leadscrew and put a drop of oil in the 
> front
> bearing, but it still does this. Any suggestions??
> I have the PTO on the bench, coupled to a counter. The freq. was off quite 
> a
> bit (~2kHz) after 10 turns. I have adjusted the endpoint slug and now have
> it within 700Hz. I have a pointer knob on the shaft, and have been setting
> the PTO at 3455.0 and marking the front plate, then after exactly 10 turns
> (2455.?) I see where I am relative to the starting mark and make another
> tweek of the slug. Back to 3455.0, another mark and do it all over again. 
> Is
> there an easier way to make this adjustment?? I'd like to get it closer, 
> but
> all this back and forth is driving me to drink!!
> Looking forward to your comments and suggestions.
> Roger Gates, W7KVT
>
> Thank you Fellows,
> Merry Christmas to all
>
> Roger Ruszkowski  AI4NI
>
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