Panasonic RS-B25 - Gain and Meter Calibration

RS-B25
7. Place UNIT into CrO, tape mode.
8. Change test tape to CrO, reference blank test tape
(QZZCRX), and record 1kHz, 50Hz, 100Hz, 200Hz, 500 Hz,
4kHz, 8kHz, 10kHz and 15kHz signals. Then, playback
the signals and check if the curve is within the limits
shown in the overall frequency response chart for CrO,
tapes (fig. 14). an
9. Place UNIT into metal tape mode and change test tape to
metal reference blank test tape (QZZCRZ), and record
+50B
a
1kHz, 50Hz, 100Hz, 200Hz, 500Hz, 4kHz, 8kHz, 10kHz, iin
12.5kHz and 15kHz signals. Then, playback the signals |
Eile iil
TH
and check if the curve is within the limits shown in the aH oi ait
overall frequency response chart for metal tapes (fig. 14). SOHZ 100Hz 200Hz SO0Hz 1kHz 2kHz 4kHz 10kHz12.5kH2
10. Confirm that bias currents are approximately as follows Fia. 14
when the UNIT is set at different tape mode. g-
*Measure the voltage across the head using a EVM.
Overall frequency response i sit Metal)
+6dB Mea mean +6dB
around /7.7V (Normal position)
Standard value: around 13.3V (CrO, position)
around 18.3V (Metal position)
@ Overall gain Condition: Equipment:
e Record/playback mode * EVM (Electronic Voltmeter) ® AF oscillator
* Normal tape mode e ATT ¢ Oscilloscope
e Input level controls... MAX e Resistor (6009)
¢ Standard input level; e Test tape
MIC ............... -72 +5up (reference blank tape)
-3 ...QZZCRA for Normal
LINEIN .........
. Test equipment connection is shown in fig. 15.
. Insert the normal reference blank tape (QZZCRA).
. Place UNIT into record mode.
: ee a 1kHz signal through ATT (—24dB) from AF oscillator, to LINE
. ae ATT until monitor level at LINE OUT becomes 0.4V.
6. Playback recorded tape, and make sure that the output level at LINE
OUT becomes 0.4V.
7. If measured value is not 0.4V, adjust it by using VR7 (L-CH) or VR8
(R-CH).
. Repeat from step (2).
AF oscillator
@ LED meter Condition: Equipment:
e Record mode © EVM (Electronic Voitmeter) ¢ AF oscillator
¢ Input level controls...MAX ¢ ATT * Oscilloscope
¢ Resistor (600Q)
. Make connections as shown in fig. 15.
2. In the recording pause mode, apply 1kHz (—24dB) to LINE
IN. Peak level meter
3. Adjust ATT so that output level at LINE OUT is 0.4V. Creve) Met a afm ge g(t]
4, At this time, check that 0dB indicator is lighted halfway [right Tevel i i [right]
(intermediate brightness between full brightness and light- -o 30] 3 +6 dB
out: See fig. 16).
Fig. 16