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15.1.2 DISPLAY BOARD ADJUSTMENTS
The display board is pre-adjusted during testing. However, when installed in the amplifier, most adjustments need to be fine-tuned.
Remove the front panel glass to gain access to adjustments.
15.1.2.1 1. PLATE CURRENT (Adjustment: VR4, Marked: AMP)
Connect a power supply to pin TP2 on the control board: negative to TP2, positive to the chassis.
Apply a current with a value between 1 A and 2 A. Choose a convenient value close to the full scale on the Ip LED row on
the display board.
Adjust potentiometer AMP for correct indication.
15.1.2.2 2. PLATE VOLTATE (Adjustment: VR2, marked: VOLT)
Using a voltmeter with a high voltage probe, measure the plate voltage.
Adjust potentiometer VOLT for correct indication on the display.
15.1.2.3 3. REFLECTED POWER (Adjustment: VR3, marked: RF R)
Reverse the input and output RF connections:
- connect the transceiver or exciter to the output
- connect the dummy load to the input of the amplifier
Apply 100W drive and adjust “RF R” for 100W indication
Reverse again the RF cable - connect them the right way.
15.1.2.4 4. FORWARD POWER (Adjustment: VR1, marked: RF F)
On 20m, operate the amplifier at the full nominal power, as indicated by an external power meter:
1500W for DX-2
2000W for DX-2SP
3000W for DX-3
Adjust potentiometer “RF F” for correct display indication
15.1.2.5 5. SCREEN CURRENT (Adjustment: VR6, marked IG2+, VR5, marked IG2-)
ig2-: put VR5 in the middle position
ig2+: connect a mA meter in series with the screen supply, between the control board pin EG2 and the blue screen wire.
(See also the control board adjustment for IG2 LIMIT).
Generate a current in the mA meter, either by connecting a load, or by operating the amplifier close to full power.
Adjust VR6 for 4 LED's on, at the limit of starting to flash, for a current ig2+ of about 50mA.
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