Carl,
My passband tuning knob rotates 360 degrees on my R-4A. It was very scratchy
and draggy (metal on metal) until I cleaned and relubricated it. The key was
that I was told to unsolder the left side metal cover where it is tacked at the
top, front and back. This gave me just enough so I could bend it out enough to
clean things up in there. Its still tight, and you can't see great, but you
can see enough. I used repeated applications of Q-tips and alcohol and when it
still felt scratchy I put a little TV tuner lub/grease on the wobble disc. The
4 tuning slugs (visible through four 3/8 holes in the rear) should be at their
maximum rearward travel when the knob is at the 9:00 position. Hope this helps.
KB8BKU , Darryl in Dayton
On Jul 17, 2011, at 2:46 AM, Carl Maniscalco wrote:
Greetings to you all.
I'm new to the Drake world and I just recently traded for a R-4A/T-4X combo
that had sat unused for many years. While the equipment is in pretty decent
shape over all, all of the mechanical elements were gummed up with hardened
grease, oil and nicotine deposits (apparently, a previous owner was a heavy
smoker). I've managed to clean them up considerably and have the PTOs on both
radios working smoothly enough that I can easily tune across the band with
one finger.
The passband tuning on the R-4A is giving me some trouble, however. The inner
shaft was frozen up completely and I was forced to remove the read panel of
the PBT unit in order to clean the gunk off the shaft and tapered disk free
it up. The problem is that, after reassembly, I'm not sure how how it's
supposed to operate because I've never seen one in woking condition before.
It seems that no matter how I adjust it, it wants to bind up a bit.
So, what I'm asking is how many degrees of knob rotation should I expect? How
should should the the screw and locknut on the rear panel be adjusted? Should
there be friction or should the knob turn freely? Should there be any end
play? Where should the thickest part of the tapered disk be when the knob is
at the 12 o'clock position?
Any help will be greatly appreciated.
73,
Carl, KJ6BSO
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