I
OSCl LLOSCOPE
I
FREQUENCY
650 A I I VTVM I STANDARD
0 1
VERT HORlZ
IN
0
J -
I
1
ELECTRONIC i
FREQUENCY
I COUNTER
I
1
Figure 4-3. Calibration and Response Check for Low Frequency Oscillator
(Figure B is suitable over entire 650A frequency range.)
CAUTION -1 4-6G LOW FREQUENCY OSCILLATOR I
T Before changing any 1/2 watt padding resistors, RESPONSE
check the other low frequency oscillator ranges a. Connect voltmeter and frequency measuring equip-
(XlO-, X100-. and XlOKC) for a possible ment as shown in Figure 4-3. 1
constant error on all ranges. If error is con-
stant. changing padding resistors for the X1K b. Repeat Preliminary Low Frequency Response
range would not be advisable. Adjustment.
I
h. Repeat step b_ then turn frequency dial to "8" and c. Check frequency response on three remaining low
measure output frequency. frequency oscillator ranges. Specifications require
a response that is flat within sl db from 10 cps to
i. If output frequency is lower than 8 KC, bend end 100 KC with a 1 KC zero db reference. Adjacent ranges I
rotor plates outward on all sections of low freq- should be within 1/2 db of each other.
uency oscillator tuning capacitor. Bend only those
segments of the rotor plates that are just meshing. d. Repeat Low Frequency Output Distortion measure-
If output frequency is high, bend rotor plates inward. ment. 1
Rotor and stator plates must not touch. Try to bend
plates equally on all sections of the tuning gang. 4-6H HIGH FREQUENCY OSCILLATOR
AMPLITUDE ADJUSTMENT
j. Repeat step iat frequency dial settings of "5", "3", 1
"2" , "1.3". and "1". Adjust plate segments without a. Measure ac voltage on plate pin 5 of V4 buffer amp-
changing those that have already been adjusted. Bring lifier stage. With range switch at "X100KC" and
calibration to within approximately 1%. FREQUENCY dial at "1" (100 KC output signal) this
voltage should be 1.1 volt, kO.1 volt. Instruments with I
k. Check frequency calibration of remaining low fre- Serial No. 1649 or below should be modernked.
quency oscillator ranges. These ranges should be b. High frequency oscillator voltage is adjusted by
within 1% calibration specifications. If they are not,
change padding resistors for range that is off freq- changing tubes V1, V2, V3, and/or V5. To raise I
oscillator voltage: install tubes with a higher trans-
uency as described in step g. conductance for VI, V2. and V3 oscillator stages and/
or a tube with lower transconductance for V5 AVC
1. Calibration at 100 KC with range switch on "XlOKC" amplifier tube.
and FREQUENCY dial at "10" can be adjusted by 1
changing value of capacitor C25 in cathode circuit of c. If oscillator voltage is too high, install a tube with
Vl1 low frequency oscillator tube. higher transconductance for V5 AVC amplifier.
-20- |
ACEC
HEWLETT-PACKARD
