Audio Circuit; Audio Rec Fm; Syscon Circuit [Sr-Vs20E]; Timer Clock - JVC SR-VS20E Service Manual

3.4 AUDIO CIRCUIT

Notes:
• This adjustment should be done after the "REC color
(colour) level adjustment" for the video circuit has
been completed.
• GND (Ground) should be taken from the Tuner shield
case.

3.4.1 Audio REC FM

•
Signal (A1) Ext. input
•
(A2) Audio: No signal
•
(A3) Video: Color (colour) bar signal [PAL]
•
Mode (B) S-VHS LP
•
Equipment (C) Oscilloscope
•
Measuring point (D) TP2253 (A. PB FM)
•
External trigger (E) TP111 (D.FF)
•
EVR mode (F1) Jig RCU: Code "57"
•
EVR address (F2) A: 30 (Press remote controller "3"
and "0" keys.)
•
Specified value (G1) 450 ± 100 mVp-p
•
(G2) More than 300 mVp-p
•
Adjustment tool (H) Jig RCU [PTU94023B]
•
Digit-key remote controller
(1) Apply the external trigger signal to D.FF (E) to observe
the Audio PB FM waveform at the measuring point (D).
(2) Record the signal (A3) with no audio signal input in the
mode (B), and play back the recorded signal.
(3) Press the channel buttons (+, –) simultaneously to enter
the manual tracking mode. This also brings tracking to
the center (centre).
(4) If the A.PB FM level is not within the specified value (G1),
perform the adjustment in a following procedure.
(5) Set the VCR to the EVR mode by transmitting the code
(F1) from the Jig RCU.
(6) Set the EVR address to (F2) by pressing the button of
the digit-key remote controller.
(7) Adjust with the channel buttons (+, –) on the VCR (or on
the remote controller) so that the A.PB FM level of the
higher channel level becomes the specified value (G1).
(Adjust before recording, then confirm it by playing back.)
(8) If the specified value (G1) is not obtained, adjust with the
channel buttons (+, –) so that the waveform level of the
lower channel level becomes the specified value (G2).
(Adjust before recording, then confirm it by playing back.)
(9) Release the EVR mode of the VCR by transmitting the
code (F1) from the Jig RCU again. (When the EVR mode
is released, the adjusted data is memorized.)
Specified
value (G2)
V. rate
Fig. 3-4-1a
Specified
value (G1)
Audio REC FM

3.5 SYSCON CIRCUIT [SR-VS20E]

Note:
• When perform this adjustment, remove the Mechanism
assembly.

3.5.1 Timer clock

Signal (A) • No signal
Mode (B) • EE
Equipment (C) • Frequency counter
Measuring point (D1) • IC3001 pin 61
Short point (D2) • IC3001 pin 24
(D3) • C3026 + and –
Adjustment part (F) • C3025 (TIMER CLOCK)
Specified value (G) • 1024.008 ± 0.001 Hz
(976.5549 ± 0.0010 µsec)
(1) Connect the frequency counter to the measuring point
(D1).
(2) Connect the short wire between the short point (D2) and
Vcc (5V).
(3) Short the leads of capacitor (D3) once in order to reset
the microprocessor of the SYSCON.
(4) Disconnect the short wire between the short point (D2)
and Vcc then connect it again.
(5) Adjust the Adjustment part (F) so that the output fre-
quency becomes the specified value (G).
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