HP 654A - Frequency Adjustments

Model 654A Section V
5-42. TURN- ON.
543. Connect the 654A to a variable power line supply
(set for 115V or 230V as appropriate).
5-44. Zero set the meter ( Paragraph 3-7), turn the
instrument on ( Paragraph 3-8), and allow 30 minutes
warm-up time.
5-45. POWER SUPPLY VOLTAGE ADJUSTMENTS.
a. Connect a dc voltmeter to the power supply
positive output ( Al Pin 12).
b. Adjust Al R14 (+ 30V Adjust) for 31, +/- 0.2V.
c. Connect the dc voltmeter to the power supply
negative output ( Al Pin 13). The voltage should
be - 26, +/- 0.5V; if not, change the value of
Al R15* to obtain the required voltage ( increasing
the value of A1R15* makes the power supply
voltage less negative, and vice-versa).
d. For power supply troubleshooting, refer to Para-
graph 5-78.
5-46. POWER SUPPLY REGULATION AND RIPPLE
CHECK.
a. Connect the dc voltmeter to the power supply
negative output ( Al Pin 13); switch the
FREQUENCY RANGE switch to X100 and note
the voltmeter indication.
b. Vary the power line voltage from 103.5V to
126.5V ( 207V to 253V for a 230V power line);
the de voltmeter indication should remain within
+/-0.5V of the reading noted in step a.
c. Adjust the line voltage to 103.5V ( 207V for a
230V power line) and disconnect the dc voltmeter.
d. Connect an oscilloscope to the power supply
positive output ( Al Pin 12) and short out the
tuner capacitor ( Cl) by clipping a lead from the
solder lug ( green/white lead) on the tuner frame to
the chassis. The oscilloscope ripple indication
should be less than 15mV peak- to- peak.
DO NOT MOVE THE TWO WIRES BE-
TWEEN TUNER AND RANGE SWITCH;
THEIR POSITION WILL AFFECT
FREQ. CAL.
e. Connect the oscilloscope to the power supply
negative output ( Al Pin 13); the ripple indication
should be less than 15mV peak- to- peak.
f. Disconnect the clip lead from the tuner.
5-47. FREQUENCY CALIBRATION PROCEDURES.
DO NOT MOVE THE TWO WIRES BE-
TWEEN TUNER AND RANGE SWITCH
AFTER CALIBRATION IS STARTED;
THEIR POSITION WILL AFFECT
FREQ. CAL.
5-48. The frequency calibration set-up is shown in Figure
5-14 ( do not make the set-up at this time); the frequency
should be continuously monitored at the rear panel
COUNTER OUTPUT. Table 5-2 lists the accuracy required
at each check frequency; adjustments for each range are
listed in Table 54. Components located on the FRE-
QUENCY RANGE switch ( S2) are identified on the switch
drawing of Figure 7-2.
Table 5-4. Frequency Adjustments
Increasing value of these components decreases frequency and changes A2TP2 voltage as shown. Adjust
variable capacitors clockwise to increase capacitance, counter- clockwise to decrease capacitance.
FREQUENCY
RANGE
FREQUENCY
Increases
A2TP2 Voltage
Dial = 1
Decreases
A2TP2 Voltage
FREQUENCY
Increases
A2TP2 Voltage
Dial = 10
Decreases
A2TP2 Voltage
X10
X100
X1K
X1OK
X100K
X1M
S2R2*
- - -
- - -
.
- - -
S2R8*
S2R10*
- - -
- - -
---
---
S2R16*
- - -
S2C17*
S2C8, S2C9*,
S2C13*, S2C16*
S2C1*, S2C18*
S2C10, S2C11*
A2C1 , S2C12,
S2C15*
- - -
- - -
S2C2, S2C3*
- - -
S2C4, S2C5*
S2C6, S2C7*
5-13