HP 400D Operating And Servicing Manual page 21

Tube
-
VI 6CB6 Cathode
-
V2 6CB6 1st
-
V3 6CB6 2nd Amplifier
-
6CB6 3rd Amplifier
V4
-
V 5 6CB6 4th Amplifier
-
V6 6AX5 High Voltage Rectifier
V7 - 12B4.. 1 \ Power Supply Series Regulator
-
VB 6UB �wer Supply Control Tube
-
Vll
5651 Reference Tube
Special high - performance junction type silicon diodes
are used for CRI and CR2.
are manufactured by ® and are available directly
from the factory or from your I(j Representative.
The cathode end of the diodes has a gold plated wire
is
also coior coded green. The anode end has
and
a silver plated wire.
These diodes have a junction that is less than 1/2
if
mil in diameter and, dropped, a mechanical failure
may occur at the junction. After installation the
diodes will withstand any shock that the entire instru­
ment can withstand.
Voltage calibration and frequency response should
be checked and adjusted after replacing
V4, VS, CRI, or CR2.
4-5 REQUIRED TE5T EQUIPMENT
The following eqUipment is required to test and
calibrate $Vacuum Tube Voltmeter Models 4000,
400H, and 400L.
i) A dc voltmeter capable of measuring 250, 6. 3,
12.6 volts. This voltmeter must have a sensitivity
of 1000 ohms/volt or better. A vtvm such as the
$Model 410B Is satisfactory.
An
2) � Spec. 23678 Voltmeter Calibration Generator
The
or equivalent. Spec. 2J678 generator will de­
liver a 400 cps output voltage from 0.3 milllvolt
rms to 300 volts rms with an accuracy of
TABLE 4-1, TUBE RE PLACEMENT
Function
Follower
Amplifier
These special diodes
VI,
V2, V3,
±O. 25% and
Circuit Adjustment
DC Heater Voltage,
Rapid Performance Check,
Rapid Performance Check,
Regulated power supply,
not more than 0.2% hwn and distortion, This gener­
ator will also supply dc or -dc voltages from 0.3
+
millivolt to 300 volts for
3) An � Spec. 23679 VTVM Frequency Response
Generator. This generator has an internal signal
SOurce to cover the frequency range from 350 kc to
to 3
11 mc. Up a volt output
tained. The internal attenuator and reference volt­
meter are designed for frequencies from 10 cps to
11 mc. Internal impedance is 50 ohms.
4) An $Spec. 23680 Wide Range Oscillator. This
oscillator has an internal impedan,,:e of 50 ohms
will
and deliver a 3 volt signal from 5 cps
Use with Spec. 23679 VTVM Frequency Response
Generator.
5) A square wave generator capable of delivering
a 2 volt peak - ta - peak
1 kc Signal, The <&1>Model 2UA
Square Wave Generator or the internal calibrator
the
in I$Model lSOA High Frequency Oscilloscope can
be used.
6 ) A high frequency oscilloscope such as the ®Model
150A.
7) An adjustable line voltage source with meter
a�curate to within I volt.
The � Spec. 23679 VTVM Frequency Response Gen­
erator and the ®; Spec. 23680 Wide Range Oscillator
are designed to be operated together when making
frequency response measurements. These two in­
struments greatly increase the speed and accuracy
of frequency response measurement.
PI
Sect. Page 3
paragraph 4 - 7C
paragraph 4-6
paragraph 4-6
paragraph 4-7B
of de
calibration volbneters.
signal call
also be ob­
to
600 kc.