[R-390] Cosmos PTO, FINAL Chapter!

[Phil Atchley]

Hi.
I know, y'all are saying, sure, sure, we've heard that before 8^)

However, I DO finally have a very sweet PTO mounted in the '67 EAC.  =
After
totally killing the original unit yesterday, (and I still don't know =
what
happened, I could find nothing wrong, it just refused to work any more.) =
I
decided the ONLY recourse was to rebuild the Parts unit that I'd =
received.
It had already donated its linearity ring and tube to the other PTO.  It =
had
a bad coax cable, VERY frozen end point adjustment (it was actually =
corroded
white and WOULD NOT budge) and a couple other minor issues.

The first order of the day (after church) was to tear down the original =
PTO
and remove its coax cable, end point coil, linearity ring, tube, =
linearity
screw disk (with the slotted screws) etc.  I then turned all linearity
screws fully counter-clockwise then one turn clockwise.

After thoroughly cleaning the parts PTO with alcohol, lightly greasing =
the
linearity plunger, linearity gears, lag screw etc I carefully assembled =
the
"new" unit, using all the best parts from both PTO's. =20

Then I installed it in the receiver (without screwing it down), let it =
get
good and warm and proceeded to align it.  From the time I started =
adjusting
the end points till I had run through it the "second time" to double =
check
it took me less than 2.5 hours total!  It really tuned up nicely with no
repeatability problems.  When I reached the 475 KHz spot it had gone -1 =
KHz
and my screws wouldn't back out far enough to compensate (1 turn, =
remember).
So I re-zeroed my Veeder counter there and started back at the =
beginning.
This time I was able to get through the entire PTO range (PLUS an extra
screw on either end for good measure).  Worst case is well under 200 Hz =
and
that is primarily due to "slop" in the way I was doing it in the =
receiver.

The double check turned out well.  Not one screw had to be re-adjusted!

NOW, I'm taking a hard earned break and do some beacon chasing in the
longwave band (IF the noise isn't too high).  Tomorrow I'll do a =
complete
alignment on the receiver and HOPEFULLY nothing else will rear its ugly
head.  If all goes well it should be in the cabinet and ready to do some
DXing tomorrow evening!

NOTE:  Before the linearity screws were dead in the middle of the window =
at
the 25 KHz points.  On this unit the screws were centered at about -12.5
KHz, exactly at the halfway points.  So, I just compensated on the =
frequency
I was looking for (my counter was again using zero beat on the Yaesu =
VR-5000
in LSB mode).  AS NOTED ELSEWHERE, IT IS IMPORTANT THAT THOSE LINEARITY
SCREWS BE CENTERED IN THE WINDOW!!               =20

73 de Phil, KO6BB

****************************************************
*  DXing THE WORLD WITH THE FOLLOWING EQUIPMENT.   *
*  RECEIVERS:                                      *
*    '67 EAC R-390/URR Surplus Receiver.           *
*    YAESU VR-5000 Wideband,  REALISTIC DX-392.    *
*    Home built Longwave "Hybrid" CW receiver.     *
*    Others which pass thru or are waiting repair. *
*  ANTENNAS:                                       *
*    Coil Loaded 18.5 Meter Long Sloper.           *
*    Roof mounted Hustler 6BTV 6 band Vertical.    *
*    Scantenna Scanner antenna at 7 Meters high.   *
*  LOCATION: Merced, Central California.           *
****************************************************




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