R.V.R. Elettronica 4CX7500, Technical Manual

Page: 60 / 82

Date: 25/07/03 R.V.R. Elettronica S.r.l. (BO) VJ10000-TE - R.F. Tube Amplifier
60
CHAPTER 6
ADJUSTMENTS
NOTE: THESE OPERATIONS MUST BE EXECUTED BY VERY QUALIFIED TECHNICIANS
AND EQUIPPED WITH NECESSARY INSTRUMENTS. UNCORRECTED OPERATIONS CAN
CUASE A SERIOUS DAMAGE OF THE EQUIPMENT AND CAUSE AUTOMATICALLY THE
RESOLVING OF THE WARRANTY.
6.1 FREQUENCY CHANGE
To execute a frequency change on a tube amplifier, it’s necessary to execute the following
operations:
1) Connect, at first time, only the exciter (30 W max, example PTX30-UHT) to the input of the
VJ10000 amplifier, excluding eventual drivers.
2) Adjust the power control of the exciter for minimum output power.
3) Switch on the amplifier and preset the command PLATE in function of the working
frequency.
4) After the heating time and obtained the exciter locking on the working frequency, increase
the output power of the exciter until 20 W.
5) Enable and act on INPUT LOAD and INPUT TUNE commands to reset the input reflected
power.
6) The last operation will be able to cause an increasing of the anode current; now, act on
OUPUT TUNE and OUPUT LOAD commands to obtain the maximum output power
readable on the wattmeter. Place the DIR/REF selector on DIR position. Verify that the
threshold bar move to internal position of RF cavity each time that we are near to the 108
MHz frequency and to external position respect the cavity when we are near to 87.5 MHz
frequency.
7) Increase the input power and adjust the OUPUT TUNE and OUPUT LOAD commands to
obtain again the maximum output power.
8) Replace at the minimum value the output power of the exciter and switch off it.
9) Insert the driver between the exciter and amplifier.
10) Switch on both the exciter and the driver.
11) Increase the output power of the exciter and execute again a fine OUPUT LOAD and
OUPUT TUNE adjustment and INPUT LOAD and INPUT TUNE adjustment until to obtain
10 KW of output power.
12) When the 10 KW is obtained, execute small adjustment with the same procedure until to
obtain the same output power with the minimum value of the plate absorption, eventually
decrease the exciter power.
APPENDIX A
CIRCUIT DIAGRAMS AND LAYOUTS