User's Manual

PINEAPPLE TECHNOLOGY, INC.
UTX2K ULTRA Operating and Service Manual
VIII -- ADJUSTMENTS AND TUNING
V
III --- ADJUSTMENTS AND TUNING (Page 1 of 2)
The UTX2K ULTRA is a new series of transmitters offered by Pineapple Technology, Inc. The
latest in LDMOS device and circuit technology are employed to ensure reliable and serviceabl
e
operation for many years.
There are very few adjustments necessary to maintain full service condition. The following will
give the technician a general overview of locations for locating these adjustments:
1. MODULATOR - See details for all adjustments in the Manufacturer's Instruction Manual
provided with your transmitter. Should you have any questions, contact the Pineapple
Technology, Inc Engineering staff for assistance.
2. BPU3KW - The bandpass filter provided with your transmitter has been tuned at the factor
y
and adjustments should not be necessary and are not recommended. Any attempt to tune
or modify this filter will void manufacturer's warranty.
3. U500LD - This is the main PA board in the transmitter. Under normal operation, no adjustments
are necessary. In the unlikely event that a power transistor has to be replaced, the bias
adjustments should be reset to insure optimum operation of the transmitter. The following
procedure should be followed when making bias adjustments:
a. Remove the PA1K amplifier assembly from the transmitter and set it up on a
sturdy work bench. The bench should be equipped with a 32 VDC power supply wit
h
current capacity of 10 Amps. A VOM will be required to measure the voltage dro
p
across the precision resistors located on the monitor board.
b.
A
ttach 50 ohm load resistors to the input port and one to the output port.
If this is not done, severe damage to the PA is possible resulting in costly repair.
c.
Connect the 32 VDC supply to the DC ± terminals. DO NOT TURN THE POWER SUPPLY
ON AT THIS TIME.
d. Locate the circuits where bias adjustments are necessary. Adjust only those circuits
where service was performed. Turn the bias adjustment POT's fully counter clockwise
You will find two (2) POT's for each power device with one on each gate. These ar
e
small SMT components and require gentle handling.
e. Locate the current sense resistors on the monitor board. This is a 2 watt .01 ohm
precision resistor. There is one for each device.
f. Turn the power supply on and measure the +DC to ensure that it reads +32 VDC.
g. Measure the voltage drop across the precision resistor. This should read zero (0) VDC.
Increase one of the bias POT's slowly till the meter reads 0.009 volts. Increase the
second POT until the reading is 0.018 volts. This completes the adjustment.
h. Repeat the adjustment above as necessary to set all circuit that have been serviced.
NOTICE: DO NOT USE THE BIAS CURRENT INDICATED ON THE MONITOR PANEL
OF THE ADP500 TO MAKE BIAS ADJUSTMENTS.
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