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fully counterclockwise. To do this, slightly loosen the
hex-head screws and push the detent block in or out as
necessary.
5.3.4 DQ RHEOSTAT ADJUSTMENT.
The ganged DQ
rheostats (R4 and R5) should be set to give the best over-
all tracking with the DQ dial, as determined by measure-
ment of RC networks with known D values (see paragraph
).2.4).
The dial should be positioned to give the best
tracking with the inner rheostat (R4, LOW D). Then the
rotor of the rear rheostat (R5, HIGH D) should be set on
the shaft to give the best tracking with the dial.
5.4 REPLACING INDICATOR LAMPS.
The indicator lamps are operated well below their
rated voltage and should last for many years. If they do
requite replacement, the pilot light and the two lamps
labeled INDUCTIVE and CAPACITIVE can easily be re-
placed after their lenses are unscrewed. To replace the
other lamps,
it
is necessary to remove the dress panel.
To do this, remove the eight panel screws at the edges,
the two screws directly below the meter, and all knobs
except the DQ knob.
SERVICE
AND
MAINTENANCE
In order to replace .the lamps under the DQ dial,
the dial must be removed.
Before removing the dial,
make a note of its setting so that it can be replaced ac-
curately.
The unit dial must be removed to replace the
unit indicating lamps and should be replaced in the same
position. To replace the lamps held in place by insula-
ting washers, it is easier to unsolder the connection on
the pin coming through the washer.
Be careful not to
let solder or rosin run down this pin and prevent its free
mO'lement in the washer.
All lamps are GE Type 327 miniature lamps and
are available in most hardware or hobby stores.
If un-
available locally, they are available from General Radio
Company (our Type 2LAP-7).
A schematic diagram o{ the lamp circuits is shown
in Figure 5-12.
5.5 TROUBLE-SHOOTING SUGGESTIONS.
5.5.1
BRIDGE PROPER.
a. Bridge Error. Reter to paragraph 5.2 for a cali-
bration procedure that will locate any bridge component
that is in error.
J
TABLE
5-2
DC VOLTAGES ON OSCILLATOR-DETECTOR-AMPLIFIER CIRCUIT BOARD
CONT:WL SETTINGS:
DET SENS: fully clockwise
GEl'! LEVEL: fully clockwise
Power: AC INT
BRIDGE SELECTOR: R s
RANGE: 1100 mO
CGRL: maximum
UNKNOWN terminal s open
TRANSISTOR
PIN
DC VOL TS
TRANSISTOR
PIN
DC VOLTS
(TYPE)
(TYPE)
Q525
E
11.4
Q552
E
1.82
(2N520A)
B
11.2
(2N445A)
B
1.67
C
6.4
C
4.95
E
10.6
Q553
E
2.88
Q526
(2N520A)
B
3.77
B
11.0
C
1.68
(2N 1415)
C
4.7
E
7.0
E
0.57
Q554
B
6.3
Q550
(2N445A)
C
7.9
B
0.61
(TRl)
C
1.62
E
8.1
Q555
(2N520)
B
7·9
E
1.95
C
6.6
Q551
B
1.62
OSC OUTPUT
32
2.5 vac
(2N445A)
C
3.77
DC INPUT
42
14.0 vdc
33
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