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SE RV IC E
AND
MA
I
N
T
EN AN
CE
SECTION
5
•
SERVICE
AND
MAINTENANCE
5.1
GENERAL.
The two-year warranty given with every General
Radio instrument attests the quality of materials and
workmanship in our products.
When difficulties do oc-
cur, our service engineers will assist in any way pos-
sible.
In case of difficulties that cannot be eliminated
by the use of these service instructions, please write or
phone our Service Department, giving full information of
the trouble and of steps taken to remedy it. Be sure to
mention the serial and type numbers of the instrument.
Before returning an instrument to General Radio
for service, please write to our Service Department or
nearest district office (see back cover), requesting a Re-
turned Material Tag. Use of this tag will insure proper
handling and identification. For instruments not covered
by the warranty, a purchase order should be forwarded to
avoid unnecessary delay.
5.2 CALIBRATION CHECKS.
5.2.1
FIXED BRIDGE COMPONENTS.
A calibration
check of the fixed-bridge components in the Type 1608-A
Impedance Bridge can be made by the series 'of measure-
ments listed below.
The accuracy of this calibration check depends on
the accuracy of the internal standards used. A General
Radio Type 1409-T Standard Capacitor is recommended
as a capacitance standard. This capacitor is calibrated
to ±O.03%. Type 500 Resistors are recommended as the
resistance standards.
Their accuracy is 0.05% (except
for the I-ohm unit, whose accuracy is 0.15%). More ac-
curate resistors should be used if available, or Type 500
Resistors can be measured to greater accuracy if a suit-
able bridge is available.
a.
Check of R t ' (R3). Measure a known lO-k re-
sistor on both the R s bridge (l1-kD range) and the G p
bridge (110-f.lJ5range).
The average of these two read-
ings is the error in the standard resistor R t ', and is in-
dependent of the value of the external standard used.
(Actually,' it is the difference between the centade R n
and R t , but the centade is more difficult to adjust and
can !;lave any value as long as R t and C t are set.) R t
can be easily shunted, preferably with film resistors to
TABLE 5-1
RATIO ARM CHECKING PROCEDURE
( Refer
to
paragraph
5.2.1.)
EXT STD
BRIDGE
RANGE
R
a
RESISTOR
+ERROR
MEANS R
a
1D
R s
1100MD
R7
too small
lOD
R s
lID
R8*
too small
100D
R s
110D
R9*
too small
1k
R s
1100D
RIO*
too small
1k
G
p
1100 flU
R14*
too large
10k
G
p
110 flU
R15
too large
lOOk
G
p
11 flU
Rll
too large
1MD
G
p
1100nU
R13
too l'<lrge
*
Actually, the ratio arms for their ranges are the sum of several re-
sistors, but if the previous measurement is correct, the indicated
resistor is the component in error.
31
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