the regulated voltage should measured be and adjusted as necessary,
as described in paragraph 4-6. When any tube in the regulator cir -
cuit is replaced, a check also should be made to make certain that
the regulated voltage re mains essentially constant when the line volt -
age is varied from 105 to 125 volts (or from 210 to 250 volts, on
230 volt operation). Since failure to regulate over this range usually
is a function of tubes, regulator tubes should be replaced as neces -
sary to obtain satisfactory regulation.
If tube V3, V4, V5, V6, or V7 is replaced, the gain of the selective
amplifier should be checked as described in paragraph 4-8.
4-3 REPLACEMENT OF LAMP R13
Lamp R13 has an extremely long life, theoretically almost infinite,
and should not have to be replaced. Since the lamp contrdls the a-
mount of negative feedback in the oscillator circuit, if for any rea-
son the lamp should fail, the voltage generated at the output of tube
V2 should be measured after the replacement lamp has been in-
stalled.
Measurement and adjustment of the oscillator output are described
in paragraph 4-7. If the adjustment does not bring the oscillator
output voltage within the specified limits, the replacement lamp
should be rejected and another lamp installed. The test procedure
should then repeated. be
4-4 VARIABLE RESISTORS
Should any of the variable resistors require replacement, connec-
tion should be made as shown in Fig. 7.
If resistor R18 is replaced, the oscillator output voltage should be
measured and adjusted as described in paragraph 4-7.
If resistor R69 in the voltmeter circuit is replaced, the procedure
for calibrating the voltmeter (see paragraph 4-10) should per- be
formed.
If resistor R81 in the voltage regulator circuit is replaced check
the level of the regulated voltage and adjust R8 1 as necessary, as
described in paragraph 4-6.
If resistor R96 is replaced readjust the gain of the selective am-
plifier, as described paragraph in 4-8.
If resistor R74 is replaced, check the 600G output as described in
paragraph 4-11.
If resistor R79 in the filament supply is replaced, readjust the
hum balance as described paragraph in 4-9. |
ACEC
HEWLETT-PACKARD
