EFJohnson 764X - Manual (Page 59)

ADJUSTMENT PROCEDURE
6-4
November 1998
Part No. 001-7600-001
in the upper part of the screen is for the currently
selected channel.
5. To move the cursor between the parameters on the
left side of the bar graph, press the
↑ ↓
arrow keys.
To change a parameter, press the
← →
, PgUp/PgDn,
backspace, or spacebar keys. Refer to the individual
adjustment descriptions for more information on the
functions performed using this screen.
6.1.5 REPROGRAMMING IF EEPROM IS RE-
PLACED OR ERROR OCCURS
When EEPROM IC3 is replaced or if the trans-
ceiver displays an error message and beeps, the fol-
lowing operation must be performed before making
any adjustments.
1. Using the programming software, read (download)
the data programmed in an exact same version of
the transceiver. Refer to Section 4.4.4 for more
information on reading data.
2. Select the MODEL menu and press the down arrow
(
↓
) key. Type “RESERVE” and press (ENTER).
The “Reserved” indicator should begin flashing in
the upper right corner of the screen.
3. Connect the computer to the transceiver that had the
EEPROM replaced or is displaying the error (see
Figure 4-1). Write the current data to that
transceiver.
6.2 PRELIMINARY SETUP
1. Preprogram the transceiver with test channels as
described in Section 6.1.2.
2. Connect the computer test setup using the test cable
described in Sections 6.1.3 and 6.1.4. Start the
program as described.
3. Connect a DC power supply and a 50-ohm, 50-watt
antenna load to the transceiver (see Section 6.1.1).
VHF ADJUSTMENTS
6.3 PLL ADJUSTMENT (VHF MODELS)
1. Remove the bottom cover by removing four screws.
Connect a DC voltmeter to check point CP1 shown
in Figure 6-4.
2. Select the channel on the high end of the band
(Test Ch. 1 - 174.050 MHz). This is done by press-
ing the
↑ ↓
arrow keys to highlight “Memory CH”
and then pressing the adjust keys (
←
/
→,
PgUp/
PgDn, or spacebar/backspace) to select the channel.
3. Key the transmitter using the switch on the test
cable and the meter reading should be 4.3 volts. If
this voltage is significantly different, adjust L14 (it
may be necessary to remove the VCO shield).
4. Unkey the transmitter and the meter reading in the
receive mode should be 3.3 – 4.3 volts.
5. Select the channel on the low end of the band (Test
Ch. 2 - 146.050 MHz). The meter reading should be
0.9 – 1.9 volt in both the transmit and receive
modes. Replace the bottom cover.
6.4 TRANSMITTER ADJUSTMENTS (VHF
MODELS)
6.4.1 REFERENCE FREQUENCY
1. Select the channel on the high end of the band (Test
Ch. 1 - 174.050 MHz).
2. Scroll down to “TXF SET” on the screen and press
(Enter). Monitor the transmit signal with a fre-
quency counter and key the transmitter using the
test cable switch.
3. Adjust for the displayed frequency by pressing the
computer adjust keys. Unkey the transmitter.
VHF ADJUSTMENTS