[R-390] Fwd: Re: R390A Turns Counter BFO option?

[rbethman]

This is to put it out into the PUBLIC for all, as informational and 
institutional knowledge.

I asked a direct, off-line question.  This is due to the fact that I 
obtained an NOS/NIB turns counter.  I have been contemplating installing 
it as I restore my '51 Contract Collins "Blue-Striper".

Bob - N0DGN

-------- Original Message --------
Subject: 	Re: [R-390] R390A Turns Counter BFO option?
Date: 	Mon, 14 Mar 2011 19:38:48 EDT
From: 	Flowertime01 at wmconnect.com
To: 	r-390 at mailman.qth.net



Bob,
you ask,
what other modification is needed to expand the BFO range from 6Kc to 26Kc.
---
None.

Bob,
  The range of the PTO in the BFO circuit is more or less 26KC around 455KC.
YMWV.
The stock knob has a stop that limits the BFO pitch to about + - 3 KC. The
micro dial will let you jam the PTO into both of its ends points and thus
destroy the PTO if wrenched well.

Thus with the micro dial you can have the full range of the BFO to do what
ever you can imagine with it. You can also remove the stock knob stop and
achieve the same results. You can also just back the BFO knob out on the shaft
a bit so the knob dog misses the stop. Same results. You can also chop the
dog out of a knob to miss the stop. Same results.

The stock stop was installed, The knob twisted around. The findings were
about plus and minus three. Someone suggested 1KC marking and a zero point.
That was silk screened on the first R390s. It was a silk road and forever
since been engraved in metal. Once you get that stop out of the way you jump the
curb and go crashing into the forest. Why one would go off into the forest
beyond the range of audio I know not. (OK so off to high audio frequencies I
cannot hear.)

We had a lot of micro dials. They had no stops. I never had to replace a
BFO PTO core because some operator just felt a need to dial one over to the
point of breaking it.

Watch the bellows coupler. As you drive the core from end to end you do
screw the shaft in and out thus compressing and expanding the bellows. Lots of
iterations where you run the bellows open can break the bellows. A poor
adjustment can cause you to fully compress the bellows before you hit the full
range of the PTO thus you may not think you are getting the full PTO range.
You may also find that 455 is no where near the real center of the mechanical
adjustment.

Roger AI4NI</HTML>
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