[R-390] R-390 end-point adjustment

Tue, 15 Jan 2002 08:59:04 -0800

Hi, all

Apparently I was trying to tweak the temperature compensation.  Glad I asked
first!  I have put the set back together, and will find another mini-moment
to take a look at it.  Along with miniature gear, time seems to have shrunk
also.

Thanks for the notes, will carefully file them away for the next attack.
Noticed also, in tuning around that a couple of spurs have appeared, one
near 910 KHz and another at 610 KHz.  They are not loud, but doubt they
should be there.

Thanks again.  It is great to work on equipment this complex with an expert
eye or two watching over one's shoulder.

Thanks again.

73 de Bill, AB6MT
[email protected]

----- Original Message -----
From: "David Medley" <[email protected]>
To: "Bill Smith" <[email protected]>
Sent: Monday, January 14, 2002 7:59 PM
Subject: Re: [R-390] R-390 end-point adjustment

> Hi Bill. I am not sure what you have done here but here is the simple
> procedure which yields acceptable results.
> 1. Remove the PTO from the chassis. Be careful not to lose the anti
> backlash spring and the oldham coupler disk.
> 2. Remove the front mounting bracket. Three screws.
> 3. Looking in from the front you will see a large hex bolt with a
> screwdriver slot in it.
> 4. Remove this. Inside you will see a small brass screw. This is the end
> point adjustment. Be VERY careful with this. Sometimes they bind and
> excessive force will break off one side of the slot. This is a major
> disaster and requires complete disassembly of the PTO to replace it.
> 5. Connect a frequency counter to the output coax. Connect the power
> connector and set the PTO in the frame so you can reach the aforementioned
> adjusting screw.
> 6. Turn radio on and allow to stabilize for an hour. Note you only need to
> have the radio on STANDBY for this adjustment.
> 7. Manually rotate the PTO shaft until the counter reads 2.45500 MHz. Now
> using the oldham coupler disk on the shaft as an index make a mark on the
> PTO housing.
> 8. Rotate the PTO shaft ten turns and then align the index as in 7. The
> frequency counter should read 3.45500 MHx. If it doesn't rotate the
> adjustment screw until it does.
> 9. Now recheck the 2.455MHz index. It will probably not line up. Make a
new
> index mark for 2.45500MHz.
> 10. Recheck at 3.45500 MHz and make further adjustment as necessary.
> 11. Repeat steps 7-10 until no further adjustment is necessary. If you run
> out of range in the adjustment this needs a turn to be removed from the
> adjustment coil inside the PTO. I have never found an R-390 PTO needing
> this to be done. On the other hand I have struck a number of R-390A PTOs
> with this problem.
>
> If you are careful enough with this procedure you can get the end point to
> within 500Hz or better.
> At 06:38 PM 1/14/2002 -0800, you wrote:
> >Hi, have a R-390 non-a with a Collins 70H-2 PTO, with mod.
> >
> >This one is out a bit, and I have attempted to adjust the end point.  I
have
> >removed the cover from S701.  Inside is a hollow, threaded cylinder.
The
> >cylinder seems to be threaded inside and out.  Slots are cut in the end
of
> >the cylinder presumably for screwdriver adjustment.
>
> I am not sure what you are referring to here but it sounds to me like the
> thermostat adjustment. Don't fool with it!!-
>
>
> >I have attempted to rotate this adjustment, but it appears to be locked
in
> >position.  I used a small mirror to see if there was any other adjustment
> >inside the cylinder or a locking nut.  None found.
> >
> >The low point of the PTO (at 000) can be set to 3.455 KHz.  The upper end
> >then measures 2.467 KHz.
> >
> >Any ideas?  I'd hate to force the adjustment any further without knowing
I
> >won't break anything!
> >
> >73 de Bill, AB6MT
> >[email protected]
> >
> >
> >
> >_______________________________________________
> >R-390 mailing list
> >[email protected]
> >http://mailman.qth.net/mailman/listinfo/r-390
>
> end
>
> Regards
> David Medley
> 1305 Rockmoor Drive
> Fort Worth  TX  76134
>
> Check my Web Page at:
> <http://www.davemed.info>
>
>
>