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CAUTION
Sect.IV
Page 1
SECTION IV
MAINTENANCE
unless the instrument
needs
recalibration.
4-1
REMOVAL
OF CASE
On the rear cover of the instrument there are two
screws that hold the case on the instrument.
Removal
of these screws will allow the instrument to slide
forward out of the case.
4-2.
TUBE REPLACEMENT
When replacing any of the tubes, with the exception of
the rectifier,
distortion measurements
should be
made to determine whether or not the instrument
still meets the specifications set forth in the front
of this instruction manual.
Poor tubes can greatly
increase the noise and distortion components of the
output waveform.
4-3
REPLACEMENT OF ELECTROLYTIC CAPACITORS
The electrolytic capacitors in this instrument are
very high quality capacitors with a life of from five
to ten years,
4-4
REPLACEMENT
OF LAMP R11
This lamp operates well below its rating and should
have an infinite life.
The lamp may be damaged by
severe mechanical vibration.
If the lamp is damaged,
a notch may appear in the output waveform and the
oscillator voltage may be excessive.
If the lamp
opens,
the circuit will not oscillate.
If it is nec-
essary to replace the lamp, the oscillator voltage
should be checked to make certain it falls within
the range specified on the schematic diagram.
Mea-
sure this voltage between the negative terminal of
C8 and chassis (see Figure 4-3 for the location of
C8).
Adjust the value of RIO until the proper oscil-
lator output is obtained.
The tuning capacitor drive mechanism
should be
lubricated once or twice a year, the interval de-
pending upon the amount of use.
One drop of light
machine oil in each of the holes in the three bearing
projections on the back of the casting is sufficient.
4-6
230 VOLT POWER TRANSFORMER
CONVERSION
The 200AB is normally shipped from the factory with
the dual 115 volt primary windings of the power
transformer connected in parallel for operation from
a 115-volt a-c source.
The windings can easily be
reconnected in series for operation from a 230-volt
a-c source if desired.
Refer to the schematic drawing
and note the transformer primary detail,
To connect T2 for 230-volt operation,
remove the
jumpers from terminals 2-3 and 4-5.
Connect a
jumper between terminals 3-4.
Replace the 0.8
ampere slow-blow fuse with one rated at 0.4 ampere.
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