HP 203A - Frequency Dial Calibration; Variable Phase Channel Square; DC Power Supply

Section IV
Paragraphs 4-52 to 4-57
fies and clips the signal applied to the base of A8Q2,
and produces a square wave at the collector of A8Q3.
This square wave is applied to A8Q4 and A8Q5 which
form a Schmitt trigger circuit. The Schmitt trigger
isa regenerative circuit whichchanges states abruptly
when the input signal crosses а specific dc triggering
level. The output from this stage is a square wave
having a rise time of less than 0.2 microsecond with
the same frequency and phase as the sine wave signal
applied to the circuit. The output is applied to a
bridged-T attenuator.
4-52. VARIABLE PHASE CHANNEL SQUARE WAVE
GENERATOR.
ооо
4-53. The variable phase channel square wave реп-
erator operates the same as the reference phase
channel described in paragraph 4-50.
4-4
Model 203A
4-54. DC POWER SUPPLY А21, A22.
4-55. The ас power supply provides regulated +15,
-15, and -24. 5 volts and unregulated +35 volts.
4-56. CALIBRATION FEATURE.
4-57, A quick check for calibration of the frequency
dialisa comparison between instrument and line fre-
quency. The FREQUENCY dial is set to 6 (CAL) and
the FREQUENCY MULTIPLIER is settothe CAL posi-
tion Through 51ВБ а 60 cycle output from А11 is
applied to the pilot light which will mix with the 60
cycle line frequency. The pilot light will flicker at
the difference or beat rate. This rate may be adjusted
to minimum by the CAL ADJ control which slightly
affects the VFO frequency. At a minimum rate of
flicker the instrument's 60 cycle frequency will be
most пеагіу like the 60 cycle line frequency. For
checking the exact frequencies throughout the ranges
see paragraph 5-5 Frequency Dial Calibration.
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