JVC TD-W777C User Manual

4. Electrical circuit adjustment procedure
TD-W77 7 A/B/C/E/G/J/U
Perform the tape transport checks and head azimuth adjustment before following checks and adjustments.
Adjustment should be performed in the order of alignment steps.
In the steps marked with an asterisk ( * ), adjustment should be performed after replacing the heads.
Perform this adjustment with the NR switch set to OFF.
Notice : OdBs=0.775V
Checking
DOLBY
circuit
(Rec mode)
(BIAS - CUT)
Output terminal: NR.
TP
ICAO1 27) & @2
Signal input: LINE IN
Cal. level: 400 Hz,
—8 dBs
DOLBY B
(Rec)
DOLBY C
(Rec)
Check and Adjustment
Input signal (Frequency, level) | Output raise value, deviation value
1 kHz, Cal, —40 dB +5.7 dB + 2 dB
5 kHz, Cal. —20 dB +3,5 dB + 1.5 dB
1 kHz, Cal. 0 dB +98 dB
1 kHz, Cal. —40 dB
5 kHz, Cal. —20 dB
+16.2 dB *3 dB
+2.9dB+2.5dB
1 kHz, Cal. O0dB+1dB
step Item Adjustment Adjust ing Standard Remarks
point value
*2 {Confirming |Play back VTT724, then confirm {Deck —8 dBs + 0.5dB | When the head is replaced, adjust
playback that the level at LINE OUT is L: VR102 playback gain level.
gain —8 dBs + 0.5 dB. R: VR202
Adjust VR102, VR202 and VR101, |Deck
VR201 so that LINE OUT level be- L:VR101
comes —8 dBm. R: VR201
* Playback Deck A : Play back VTT739, then Deck [A] : Deck
frequency confirm that the level of 1 kHz 0.5+1dB L: a cut by —1 dB (C102)
response and 10 kHz signals is 0 + 2 dB. b cut by —2 dB (C101)
(Check only) Deck [B] : R: c cut by —1 dB (C202)
Deck B : Before adjustment, discon- 0.5+1dB d cut by —2 dB (C201)
nect a, b (L-ch) and c, d (R-ch)
so that the outputs of 1 kHz and
10 kHz signals are flat.
Adjusting Connect the frequency counter to |L801 95kHz+ 3% METAL Position
bias the C821 lead through a 1.2 MQ
frequency resistor, then adjust L801 so that
the counter reads 95 kHz.
Recording 1) NR switch: OFF For Normal |With respectto |CrO,: 12.5kHz O+2dB
frequency 2) Record a1 kHz signal at an input tape 1 kHz reference:
response reference level of —20 dB, then L:VR104 |At 12.5 kHz, Metal: 12.5kHz O+2dB
record 50Hz and 12.5kHz sig- R : VR204 0.5+0.5 dB
nals and play them back. At this
time, adjust VR104 and VR204
so that the deviation of 12.5 kHz
outputs satisfy the standard
values with respect to 1 kHz
output.
Response (dB) Increase in high frequencies
> ieediodion
Decrease in high frequencies
O 50Hz 1 kHz
Low bias current
Appropriate bias current
High bias current
12.5 kHz Frequencies
(No. 4292) 11

JVC TD-W777C Specifications

General

Brand	JVC
Model	TD-W777C
Category	Cassette Player
Language	English