[R-390] Dumb Mechanical Alignment question

[Paul Roche]

It’s always something. Indeed I was able to felt clamp loose and get PTO at 2.955 MHz with dial locked at 7.500. 

But clamp is cracked; either WAS cracked or I cracked it (I don’t think I did it). So more surgery
Sent from my iPhone

> On Jul 18, 2026, at 8:07 PM, Barry via R-390 <r-390 at mailman.qth.net> wrote:
> 
> It might be even "safer" to set the counter to 7.500mc and adjust the PTO to 2.955mc.  That would put you in a safer section of the PTO's lead screw.  From there you could set the counter to 7.000+ with some confidence you'd not run into anything.  That way, the cams and other details could be checked as well.
> 
> 73,
> Barry - N4BUQ
> 
>> I agree with this.  Once the PTO is in sync with the counter, the counter is in
>> sync with the cams, and the crystal oscillator's switch is in sync with the
>> counter and cams, then finding why things are not working is a more logical
>> thing to do.  It doesn't make much sense to do much else until those conditions
>> are met.
>> 
>> Good luck with it!
>> 
>> Barry - N4BUQ
>> 
>>> Paul,
>>> I believe that all your sensitivity problems lies just there: your PTO is
>>> ~261KHz OFF from the value it is supposed to be.
>>> I cannot explain how BC band stations could be at "the right place" on the dial,
>>> but the whole radio cannot work properly if the range of the PTO is ~262KHz
>>> higher than it is supposed to be.
>>> As Barry suggested, lock the KHz dial to 000 and turn the Oldham coupler and the
>>> PTO shaft clockwise until the measured PTO output is at 3.455 MHz.
>>> OR (highly preferable), lock the KHz shaft to the +000 position and turn the
>>> Oldham + PTO shaft clockwise until the measured output is 2.455 MHz.
>>> Why is it preferable? With the dial at 000, your PTO output is already ~2.5
>>> turns too far and internally the anti-backlash mechanism of the lead screw is
>>> very near to hit the rear holding plate. Believe me, YOU DO NOT WANT THIS TO
>>> HAPPEN.
>>> 
>>> 73, Jacques, VE2JFE in Montreal
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