Ramsey Electronics FX-440 Manual page 122

simple variable inductor at these frequencies! In our final
alignment in Stage TX, we will touch up this adjustment for 1.60
volts in TRANSMIT mode at 446.00 MHz.
7. If you have a frequency counter and know how to use it, connect it to
TP2 and adjust C81 for 424.600 MHz. This presumes you have
programmed correctly for 446.00. (446.00 - 21.40 MHz 1st IF
=
424.600 MHz.) If you do not have a fine Ramsey frequency
counter (you didn't think we'd mention another brand, did you?)
but have completed Step 6 successfully, you can still verify
receiver operation quite easily. If the frequency is too high and
cannot be adjusted any lower, install C80, 15 pf. Proceed as
follows:
8. Connect your voltmeter to pin 5 of US. Pin 5 is a corner pin near
R104. You should get a reading of at least 4 volts, this indicates
that the PLL is indeed locked. If there is less than 3.5 volts or no
voltage at this point, the loop is not locked and an assembly error
is very likely.
9. If the PLL is locked per step 8 above, it's time to listen to a signal.
Since we have no antenna connected, we' II have to listen to a
known signal from a nearby transmitter like a handheld or mobile
rig. If desired, a connection can be made to L23 (the coil left
"hanging" near the rear of the PC board) you can then connect to
a signal generator or external antenna Adjust the quadrature coil,
L 1 , for the best sounding audio signal.
10. Disconnect the DC power source before further assembly.
That's about all there is to it. The receiver either works or it does' nt.
There is very little "tinkering" that can be done. If it does not work at this
stage, it would be wise to use the "double check" brackets
I ] I ]
provided and retrace your steps. HINT: trace your work "backwards,•
beginning with your most recent steps. Make sure you thoroughly
understand the PLL frequency programming and have installed the
program diodes correctly.
If the receiver section
is
not working, going ahead with Stage M or Stage
TX is very unlikely to fix the problem. Nor is there much point calling the
Ramsey factory for a quick fix or "what do I check?" because all a
technician can really tell you
is
to double-check your work. It is virtually
imposible to trouble-shoot your unit over the phone. The unit WILL work
1
all parts are installed correctly with proper soldering.
Assuming that the receiver section is working fine we can now proceed
with the final assembly whenever you are ready to do so.
Assm. 62 FX-440