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Wideband Amplifier Check
4.9
NOTE:
For satisfactory adjustment of the bandwidth, using trimmers C3 and
ca,
the use of a sweep scanner such as the Knott Polyskanner is
essential (See para.
4.. 12. If only basic servicing equipment is
available the amplifier gain can. be checked only at the lower end
of the frequency range. If the user suspects a loss of sensitivity at
the higher frequencies and the procedure in paragraph 4. 12 is not
feasible, the p.c.b.should be returned
to
Racal Instruments Service
Departmen t for ca
Ii
bration.
4.10
NOTE:
(1)
Apply a signal to the INPUT socket of 10 MHz at 10 mV r.m.s.
(2)
Set the SENSITIVITY switch to O. 01V.
(3)
Connect an electronic voltmeter (with
son
input impedance) to the base
of 06 (junction R26/C16) via an O. 1tJF capacitor in series with a 100 ohm
resistor. All leads to be as short as possible.
(4)
Check that the overall gain is 14 dB
±
3 dB.
(5)
Repeat the test with an input of 50 MHz.
(6)
The above tests will establish the basic serviceability of the amplifier
stages. For a more advanced procedure employing a sweep scanner.
(Refer to para.4. 12).
Remote Programming Check (Option 9010 and 9011 only)
This is a practical functional check, assuming that the instrument
is connected to the customer1s remote control unit, printer and
digita I counter.
(1)
With instrument cover removed, set the remote Sensitivity program to
O.01V, O. 1V and 1V in turn and check for correct operation of relays
RLA and RLB (see para. 4.7 (4) also Fig.2.2 and 2.3 at the end of this
chapter.
(2)
With a signal applied to the INPUT of the instrument select in turn
f
10 and
f
100 at the Remo te Contro I Unit, at the same check wi th
an osci Iloscope at the appropriate;' 10 or
r
100 output that the level
at the inhibited (unwanted) output is not higher than 150 mV peak-to-
peak.
(3)
With pri nter and counter connected, check that the deci ma I poi nt
printout is correct for the input frequency.
(4)
Select various
II
ga te times
11
on the digital counter and check for
9010-9013
4 - 6
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