DRAKE L7 Manual del operador descargar pdf (Pagina 29)

Turn

off the Amplifier, disconnect the Power

Supply from the power source, replace the

jumpers removed in step c above, remove the

SWR bridge and replace the covers on the

Power Supply and the Amplifier before re-

suming operation.

5-1 1. METER ADJUSTMENT

To adjust the meters on the front panel of the L 7

proceed as follows:

a. Disconnect the Power Supply from the power

source.

b. Remove all connections to the amplifier.

c. Take the cabinet off

theL 7 by removing the six

screws that secure the cabinet on the bottom of

the amplifier.

d. Each meter has

conventional zero-adjust

screw on the lower face of the meter and may be

set to zero with that screw. To access these

screws, remove the meters by unscrewing the

two mounting tabs on each side of each

mew.

e. If resistor R20 is replaced thegrid current shunt

R16 will have to be calibrated

follows:

Defeat the interlock on the top of the chassis

by placing a book on top of theoperatingrod

(NO CONNECTIONS TO AMPLIFIER).

2. Set the Meter switch to GRID CURRENT.

3. Make the connections show in figure

5-3.

4. Adjust the 10 Ohm pot

until

the milliam-

meter indicates 0.400 Amperes.

5. Adjust

R19 until the Grid Current meterindi-

cates 400 mA.

6. Disconnect the test network.

milliameter is not available, an alternate

zithod of calibrating R19

follows:

- - -

Defeat the interlock (NO CONNECTIONS

TO AMPLIFIER).

2. Reverse the wires connected to the Plate

Meter

MI.

3. Connect a 1-1/2 Volt battery (negative to

ground) in series with a 10 Ohm potentio-

meter to pin

of the Power connector 54 on

the rear of the amplifier.

4. Adjust the 10 Ohm pot until the Plate Meter

indicates 0.400 Amperes.

5. Adjust

R19 until the Grid Current meter indi-

cates 400

mA.

Disconnect the test network and reverse the

wires on the Plate Meter to their original

locations.

The high voltage adjustment potentiometerRl7

is not user adjustable. If this needs readjust-

ment, return the L 7 to the factory for service.

See paragraph 5-1.

5-12. WATTMETER CALIBRATION

The wattmeter in the

7 was designed to keep

maintenance to

minimum. The wattmeter

passive device, and it should provide years of

service and maintain

its

calibration. If calibra-

tion becomes necessary, paragraphs

5-13

through

5-16 must be followed in sequence.

5-13. NULL ADJUSTMENT

WARNING

When making adjustments to the Watt-

meter with the exciter on, exercise

EXTREME CAUTION to avoid RF

burns. Avoid touching the Piston Trim-

mer

C53, the Antenna Changeover

Relay RLYl and all wires connected

to it.

a. With the

7 completely disconnected, turn

upsidedown and remove the rear bottom cover.

b. Connect the exciterto the RFINPUT and the 50

Ohm Dummy Load to the

OUTPUT.

c. Set the

7 Meter switch on REF 300.

d. Apply between 100 and 300 Watts of power at

MHz.

e. With the insulated alignment tool adjust the

piston trimmer

C53 for

minimum indication

of reflected power.

f. All further adjustments should be made with

the L

its

normal upright position.

5-14. 300 WATTS REFLECTED

Connect the exciter

the RF OUTPUTand the

RF INPUT to a Wattmeter (Drake WH

and

then to

Ohm Dummy Load.

b. Set the Meter switch to REF 300 and apply 300

watts from the exciter.

300 watts

not avail-

able, adjust the exciter for maximum RF output.

c. Adjust R24 so that the

7 wattmeter agrees

with the standard wattmeter or with the RF

power calculated from the

voltage measured

across the

ohm load.

5-15. 300 WATTS FORWARD

a. Connect the L 7 asin thenull adjustment (para-

graph 5-15), and inclhde a wattmeter (Drake

WH-7) between RF OUTPUT and the 50 Ohm

load. Place the Meter switch on FWD 300 and

apply 300 watts from the exciter. If 300 watts is

not available, adjust the exciter for maximum

RF output.

b. Adjust R23 so that the

7 wattmeter agrees

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DRAKE L7 Manual del operador Pagina 29

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