Digital Monitoring XR6 Manual do Utilizador descarregar pdf (Página 9)

XR3/XR6 Frequency Change Procedure Page 7 of 7

IS07012 Issue 1.0

2.4.4 FINE-TUNE RF FILTER INPUT

IMPEDANCE

Fine tune the RF filter input impedance by

adjusting inductors L3 and L5.

WARNING

To avoid personal injury, the

transmitter must be in an RF Off state

with ac power switched off during

adjustments made in this section.

(a) With the transmitter operating at 6 kW

(XR6) or 3 kW (XR3) into a 50 Ω j0

load, note the current reading on the

Delta RF current probe. The current

should be 11 A for an XR6 or 7.75 A

for an XR3 and the RF current

waveform should be lagging the RF

voltage waveform on the oscilloscope

by between 40 and 120 ns.

(b) If the RF current is not 11 A for an

XR6 or 7.75 A for an XR3 and/or the

current waveform in not lagging by

between 40 and 120 ns, adjust the

input impedance. Press RF Off and

switch off ac power to the transmitter.

(c) Gain access to the output filter and

make a small adjustment to either the

L3 or L5 inductor. Install the cover on

the output filter, apply ac power, and

press RF On.

(d) Recheck the RF current probe for

11 A for an XR6 or 7.75 A for an XR3

and the current waveform lag time.

Continue to make small adjustments

until both conditions are met.

(e) When the conditions in step (a) are

met, use an audio distortion set to

measure the transmitter’s frequency

response and distortion. The Delta RF

current probe can be used as the RF

sample for these measurements. Use

an attenuator to control the RF level

and a notch filter to notch the carrier

level by about 20 dB. Minor

adjustments may be required to L3

and L5 in order to get acceptable

frequency response and distortion

measurements.

2.4.5 ADJUST RF CURRENT ALARM

(a) With the transmitter switched RF Off

and ac power removed, remove any

resistors mounted on the pins in the

R86 and/or R87 positions on the

distribution PWB. Install a 200 Ω

potentiometer, set to 200 Ω, on the

pins in the R86 position.

(b) Apply ac power and press RF On. Set

the transmitter’s RF output power to

6.6 kW for an XR6 or 3.3 kW for an

XR3.

(c) Measure the voltage on TP9 of the

distribution PWB and adjust the

potentiometer installed in the R86

position until the voltage is 1.65 V dc ±

0.05 V.

(d) Press RF Off and switch off the ac

power to the transmitter. Carefully

remove the potentiometer from the

pins at R86 and measure the

resistance.

(e) Use fixed resistors to make an

equivalent resistance to that

measured in step (d). Install the

equivalent resistance on the pins at

R86 and R87. If two resistors are

required to make up the equivalent

resistance, install one resistor in each

location (the R86 and R87 locations

are in parallel).

(f) Apply ac power to the transmitter and

press RF On. Check the voltage on

TP9 on the distribution PWB. If the

voltage is not 1.65 V ± 0.05 V repeat

steps (a) through (e).

(g) When the RF current threshold has

been properly set press RF Off and

switch off ac power to the transmitter.

Remove all test equipment and install

all of the RF filter cover screws.

(h) The transmitter is ready to be placed

back into service.

1 2 3 4 5 6 7 8 9 10 11

Comentários a estes Manuais

Sem comentários