Panasonic RQ-2720 Service Manual page 7

3 10 ay oA t
MEASUREMENT AND
Head azimuth adjustment
Condition:
+ Playback mode
Equipment:
*VTVM
* Oscilloscope
* Test tape (azimuth)
++» QZZCFM
Tape speed accuracy
adjustment
Condition:
* Playback mode
+ Tape speed control
+++ Center
Equipment:
* Digiial electronic counter or
frequency counter
* Test tape --- QZZCWAT
Bias current adjustment
Condition:
* Record mode
Equipment :
*VTVM
* Oscilloscope
———_—___-—-
ADJUSTMENT METHODS
Monitor jack
Record/playback head Playback mode
. Test equipment connection is shown in fig. 21.
. Playback azimuth tape (QZZCFM 8 kHz).
. Adjust record/playback head angle adjustment screw (B) in fig.
22 so that output level becomes maximum.
. After adjustment lock head adjustment screw with lacquer.
vTVM
Fig. 21
Oscilloscope
Record/playback head
{B)
Fig. 22
Tape speed accuracy
1. Test equipment connection is shown in fig. 23.
2. Playback test tape (QZZCWAT 3,000Hz), and supply playback Record/otayback neat pis pack mode Monitor jack
signal to frequency counter. ae
3. Measure this frequency.
4. On the basis of 3,000Hz, determine value by following formula:
f — 3,000 Z
3,000 x 100 (%)
where, f = measured valeue
. Take measurement at middle section of tape.
Digital electric counter
Standard value: 2.5%
Adjustment method
1. Playback the test tape (middle).
2. Adjust tape speed adjustment VR102 so that frequency becomes 3,000 Hz.
Record/playback head
RIG
0d}
. Test equipment connection is shown in fig. 24.
. Place UNIT into record mode.
. Read voltage on VTVM and calculate bias current by following
formula:
Value read on VTVM (V)
102
Bias current (A) =
Standard value: 0.5+0.05mA
4. Adjust VR1.
——_—_+—
Battery check circuit
adjustment
Condition:
* Record mode
Equipment:
+ Regulated DC power supply
(Carry out this adjustment if C1, LED, etc. are replaced.)
1. Set the DC supply voltage to 3V and apply it to the DC IN jack
(Shown in fig. 25).
2. Set the tape and put the unit into REC mode.
lamp (red) lights up.
* Connect MIC terminal 1 or 2 to earth terminal 3 (Shown in fig. 26). | °
+ Make no connection to the monitor terminal. Regulated DC power supply
. Lower the supply voltage to check the voltage level at which the Fig. 25
lamp turns off. :
Then the LED
Standard value: 2.05~2.10V |
If the voltage is not within standard value, adjust in J1 MIC jack
accordance with the following procedure.
1. Set the supply voltage to 2.07 V and add it to DC IN.
2. Set the tape and put the unit into REC mode.
+ Connect MIC terminal 1 or 2 to earth terminal 3.
* Make no connection to the monitor terminal.
3. Regulate VR2 to turn the LED on, make the adjustment and then turn the lamp off.
After that, apply 3V to DC IN and then lower the voltage to check that the specification is satistied.
Fig. 26