Hello all,
A few months ago I posted an email to this reflector concerning
my FT1000MP. Many hams reported that I had a second signal,
both up and down of my primary signal on 160 meters. The
response was rewarding but no cure was reported. Reports
varied from no spurs to very loud ones. It seemed that they were
particular to the individual radio in question. Some radios had
been sent back to Yaesu with little or no improvement. Some
owners had even sold their radios because of the problem!
Since I could find no hardware modifications that would cure
the problem I assumed that the answer was in alignment. It is
quite typical that the VCO could cause similar problems so I
started there. Yes, this is the culprit and yes the problems can
be solved with careful allignment.
I used a spectrum analyzer but a second receiver could also be
used. Please note all voltage measurements before any adjustments are made.
you may have to return to the original
alignment points if you mess up. I have also included the voltage
measurements that were successful on cleaning up
my problems but they may not be the same for yours.
In the service manual look up page 3-5 that shows the PLL
MAIN loop VCO alignment. Ignore the voltage measurements
as shown but use this information for reference as to the test
points.
1- Remove the top cover
2- Locate and remove the speaker. Place to the side.
3- Remove the antenna tuner unit (has the 2 coax connectors)
Make sure to remove the coax with the red band that goes to
the second PLL loop board. Place to the side.
4- Remove the tray cover to the main PLL board- 6 screws on
top and one on the back panel
5- Locate TP4003, TC4001, TP4005 and VR4001.
6- Note the voltage on TP4003 and TP4005. Use a DVM as small
voltage changes are critical.
7- With the DVM connected to TP4003 adjust the DC voltage to
the highest voltage that keeps the radio in operation at 7.499.
should be around 13 volts. Use the trimmer cap TC4001 to
adjust the voltage. Then back off the voltage 0.2 volts.
11.6 to 11.8 volts should be good. Now check the voltage at
1.820 mhz. It should be around 4.5 volts.
8- CRITICAL ADJUSTMENT. Attach the DVM to TP4005, note
the voltage and adjust VR4001 to eliminate the spurs and
any other crud that the VCO is producing. The voltage stated
in the service manual was not correct in my radio. 1.1 volts
at the test point cleaned up the signal perfectly. The spectrum
analyzer will show the proper adjustment where a second
radio may only show improvement in the signal strength of
the spur.
9- Reassemble radio in the reverse order.
Good luck and please respond directly to me about your results:
pacer99@aol.com
If you have any questions or would like for me to align your radio please
contact me at the above email address.
Larry
N7DD
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