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Re: [TenTec] PTO Backlash help needed

To: n0jmy@hayseedhamfest.com, Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] PTO Backlash help needed
From: Jerry Kitterman <jerry.kitterman53@yahoo.com>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Sun, 31 May 2009 08:35:43 -0700 (PDT)
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
   Hi Tom,
   Hope this finds you feeling much better than you were. I have been having 
some  problems 
   of my own but I'm not gonna bore you and go into them, you have enough of 
your own
   things to take care of.
 
   There is absolutely no hurry on my part about getting a C21 done but I'm 
sure it is good
   therapy for you. The more I think about it and look at my HW16's the more 
reluctant
   I get anyway. We will just have to wait and see at this point. I know I 
promised to do this
   deal but I don't know at this point if I could let all of my hw16s get away. 
Just been a 
   part of me too long I guess. Please don't take this the wrong way Tom 
because I never
   go back on a deal, just getting melancholy in my old age I guess....hi.
 
   Been wanting to try working some of the satellites that are up there and 
working on 
   getting on the air for cheap which I'm finding out is no easy feat but can 
be done. I like
   homebrewing best anyway. Buying a satellite ready rig and the antenna setup 
to use 
   with it is way outta my league anyway.
 
   Take care and stay healthy,
 
   73
   Jerry   W9CTB
 


--- On Sun, 5/31/09, Tom NØJMY <n0jmy@hayseedhamfest.com> wrote:


From: Tom NØJMY <n0jmy@hayseedhamfest.com>
Subject: Re: [TenTec] PTO Backlash help needed
To: wa3fiy@radioadv.com, "Discussion of Ten-Tec Equipment" 
<tentec@contesting.com>
Date: Sunday, May 31, 2009, 2:51 PM


I'm very leery about celebrating too soon, so with much knocking on 
wood, I'm just going to report that the felt solution has favorably 
impressed me thus far.

I doubled over a piece of felt, cut it out, put a hole in it, and then 
slipped it over the tuning shaft of the one Century 21 which I have not 
yet disassembled.  Basically, I just stuffed it down in the hole in the 
front escutcheon, up against the lock washer that holds the dial on.  It 
does not turn with either the knob or the inner shaft.

Oddly enough, after turning the knob CCW and releasing it, it still 
visibly jumps back CW, though just a smidgen.  However, listening to 
c.w. sigs, I am unable to tell any change in frequency.  Holding  on the 
the knob for a second after stopping seems to eliminate the knob 
backlash completely.  Incidentally, this is near the full CCW of travel, 
where there was the most backlash before.

Fixes this simple always scare me, so I'm not quite ready to declare 
victory yet.  If, however, this unit continues to behave this way, I 
would say the backlash, even to someone not use to the Century 21's 
little quirks, is minimal enough as to be more than satisfactory.

I still have three more to go, though, so wish me luck!

73,
Tom NØJMY .   .

Hayseed Hamfest Co. - Multi-section Can Capacitors
for vintage Heathkit, Drake, Halli, Hammy, more...
www.hayseedhamfest.com

wa3fiy@radioadv.com wrote:
> Hi Tom.  Welcome.  Good to see you here.  I greatly enjoy your entertaining 
> and informative posts to GlowBugs.   :-)
> 
> To your question.  I'm no expert on the matter but I think the unidirectional 
> backlash is due to a spring being compressed when you turn the tuning 
> knob CCW.  That spring pressure is pushing back against the "pistol" and 
> trying to turn the Acme screw thread.  This is a case where you want a little 
> more friction in the system.  Try loosening the main tuning knob and see if 
> there is a felt washer or two between the knob and the 0-100 dial plate.  If 
> not you need one or two, can't recall what TT uses.  Hold slight pressure on 
> the knob, compressing the felt washer slightly, as you tighten the setscrew.  
> That will provide some friction between the knob and dial plate which turn at 
> different rates.  Play with that and see what you get.
> 
> There is a plastic bearing on the back end of the PTO enclosure which is 
> spaced from the enclusre by one or more flat washers under the two fixing 
> screws.  That spacing adjusts spring pressure on the screw thread which in 
> turn adjusts the pressure on the ball drive.  I sometimes play with that 
> spacing as well but I think it has more to do with eliminating slippage in 
> the 
> ball drive than in minimizing backlash.
> 
> Good luck.  The Century 21 is an interesting rig.  Sort of solid state HW-16, 
> but not quite.   :-)
> 
> 73,
> -Lee-
> WA3FIY
> 
> 
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