JVC TD-V711 - Page 10

TD-V711 A/B/C/E/G/J/U |
4. Electrical Circuit Adjustment
Conduct following adjustments after adjusting tape travel and head angle.
¢ Adjust in the following order.
¢ * marks must be adjusted when replacing head. Notice: 0 dBs = 0.775V
Adjustment and checking methods
; Dolby fee = eee | Frequency level Output value and deviation
recording sored
(=Cal. Level)
; Adjusting Standard
Playback level | 1) Playback VTT724 (1 kHz) and adjust |VR102, Adjust playback level when
VR102, 202 so that LINE OUT out- 202 replacing head.
put is — 8 dBs. (L—R channel output Electronic voltmeter impedance
difference should be within 0.5 dBs) should be over 100 kQ.
2) Check headphone output (headphone
10 kHz
VR ... maximum)
— 15 dBs+3 dB, L—R difference
VR101,
201
0.5+0.5 dB
L901 95 kHz
+1 kHz
within 2 dB.
Playback test tape VTT739 (1 kHz,
L304,
404
Playback
equalizer
With 1 kHz
as reference
NR : OFF
63 Hz : +2 dB+3 dB (Check)
10 kHz) and adjust VR101, 201 so that
1 kHz, 10 kHz output is at standard
value.
TAPE : METAL
(fix needle to gaugbe lead end
and plug to connector socket)
Connect 1 MQ to F. counter and adjust
L901 so that CN 3 5 PIN output is
95 kHz.
At METAL poisiton recording mode, ad-
just L304, L404 so that R354 and R454
end voltages are minimum.
Record 1 kHz at ref — 20 dBs input and
then record 50 Hz, 12.5 kHz.
Playback and adjust 302, VR402 so that
a deviation of 50 Hz, 12.5 kHz against
1 kHz is at standard value. (Basically,
adjust so that 1 kHz and 12.5 kHz out-
put is at standard value)
Bias frequency
adjustment
HX PRO coil
adjustment
DC voltmeter
Record/
Playback
frequency
characteristics
VR302, 402)With 1 kHz
bias as
(VR904) reference,
should be at/at 12.5 kHz
the center. |0.5+0.5 dB
(front
volume)
Ref ~— 20 dB: — 20 GB lowered
from reference input value =
— 28 dB
Adjust normal, left, right
channels.
¢Bias value of chrome and
metal tape against normal tape
is set by voltage shift.
elf bias electric current is not
adjusted correctly the recor-
ding characteristic will be as
the left diagram.
High frequency rise
High frequency lowering
Response
(dB)
Excessive bias Insufficient bias electric current
electric current -~~ Correct value of bias electric current
Freqeuncy
t2.5kHz
10 (No. 4294)