R.V.R. Elettronica PJ250-NV Technical Manual page 32

PJ250-NV Technical and Maintenance Manual
2) Place the FWD/RFL PWR selector (6 Fig.1) to the FWD position.
3) Adjust trimmer R9 placed on the directional coupler for the same
reading on the PJ250-NV's meter is obtained.
4) Switch off the amplifier.
5) Connect a dummy load 25 Ohm 500W (or 2 dummy load 50 Ohm 250W in
parallel) with a through wattmeter (e.g. BIRD mod.43) in series,
set for the reading of reflected power (SETUP 3).
6) Adjust the drive power to minimum and switch on the amplifier again.
7) Adjust the output power of the exciter to obtain a reading of 25W
of reflected power on the external wattmeter.
8) Adjust trimmer R6 placed on the directional coupler to obtain the
same reading on the PJ250-NV's meter.
5.6 ALARMS CARD ADJUSTMENT
There are three trimmers on the Alarms card that are necessary to
adjust the alarm thresholds: over-temperature (R4), V.S.W.R. (R7) and
overdrive (R21).
A) CALIBRATION OF OVER-TEMPERATURE ALARM THRESHOLD
1) Short-circuit the thermal switch placed on the RF section's heat
sink.
2) Adjust the trimmer, R4, placed on the Alarms card until the over-
temperature protection is activated, and the TEMP. led lights up.
3) Remove the short-circuit on the thermal switch and verify that the
TEMP. led goes out.
4) Repeat this procedure again to verify the correct trimmer R4
adjustment.
R.V.R. Elettronica S.r.l. (Bo)
SETUP 3
Pag. 32