[Collins] 70K-2 PTO

[Ian]

David,

Were it mine I'd do what I've done with most of the Collins S-Line gear that
I have.

I would suspect that several things are happening.  The most likely item is
that the PTO needs a thorough cleaning and new lubrication.  

Of course if you don't want to do the work, you can do the best you can to
make sure that things are adjusted as well as possible.  However if the PTO
isn't rotating freely I suspect you'll find that nothing you do returns the
operation to the way it should be.

Every S-line receiver, transmitter or transceiver that I've had I've done
the PTO reconditioning.  It's made the difference between having a PTO that
worked OK but didn't really tune smoothly the way I remembered it should or
tuning as it should like the S-line units tuned in the "olden days."  After
the work on the PTO plus cleaning of the rest of the drive parts and
adjusting the behind panel hardware and cleaning the split washers that mate
with the plastic dial mechanism, I could honestly say that it worked "like
new."

Of course, in that process you need to reassemble the PTO with the shaft
position correct and get the end points where they belong.  I've done it
both with a cheap counter.... Radio Shack $40 or so on clearance.... and
I've also did it just using another calibrated (Collins, of course!)
receiver to listen to the PTO frequency.

While I have the unit on the bench I also remove the rack hardware and also
clean all that and remove the hardened grease with a soak in solvent, often
overnight.  BE CAREFUL BECAUSE THERE ARE BALLS  in the front area that form
the vernier of the preselector.  They may not be obvious when you remove a
really gummy shaft and, of course, there's a bearing at the back end that
you also watch out for.  (That's why I always do the work in a baking pan to
make sure I don't lose something while I disassemble and remove the old
grease.)  

If you carefully measure the slug positions and perhaps count turns if you
remove them you can probably return things to the way they were though now's
a good time for a tweaking of the alignment.  And do be careful around the
bands on the assembly as many of them aren't as strong as they used to be -
particularly if somebody has been messing with them in the past.

After that job and care with reassembly and adjustment of the tension at the
back end of the shaft, I've always been able to say that the preselector
tuning is just like new as well.  Nothing really seems to help a preselector
that hasn't been turned from end to end for decades while the poor piece of
gear was stored in much less than a desirable environment.  I've actually
had some S-line equipment that when I got it the preselector would hardly
move.

My experience has been that if I do these non-electrical chores I end up
with a unit that works like new.

Ian, K6SDE


> >>-----Original Message-----
> >>From: collins-bounces at mailman.qth.net
[mailto:collins-bounces at mailman.qth.net] On
> >>Behalf Of David Murman
> >>Sent: Saturday, November 17, 2007 6:46 AM
> >>To: collins at mailman.qth.net
> >>Subject: [Collins] 70K-2 PTO
> >>
> >>I have a KWM-2A RE that was built about 1972 and when I rotate the main
> >>tuning dial there are areas  that the knob moves but the frequency does
not
> >>unless you put pressure on the tuning knob. Makes it difficult to tune
in a
> >>sideband signal. I have tried to tighten the bushing but doesn't seem to
> >>help and if you get it off the wheel it is a bear to get back on.
> >>
> >>Will this remedy the problem I have or can someone point me in the right
> >>direction. I have a 312B-5 that I use for the transmit side.
...stuff removed...
> >>Thanks;
> >>David
> >>WA4ECM