3-5
3.5 DEMODULATOR CIRCUIT
Note:
•
Unless otherwise specified,set an audio multiplex TV
signal generator as follows;
RF signal : 70 dBµ / 75
Ø
, color bar 87.5% modulation.
3.5.1 Input level
Signal
(A)
• RF signal (Audio: mono 300 Hz)
Mode
(B)
• Tuner
• EE
Equipment
(C)
• Audio level meter
Measuring point
(D)
• IC1501 pin 26 [Demod board]
EVR mode
(F1)
• Jig RCU : Code “57”
EVR address
(F2)
• A : 20 (Press remote controller “2”
and “0” keys.)
Specified value
(G)
• 500 ± 10 mVrms
Adjustment tool
(H)
• Jig RCU [PTU94023B]
• Digit-key remote controller
(1) Set an audio signal mode of the RF signal generator to
mono 300 Hz.
(2) Connect the equipment (C) to the measuring point (D).
(3) Set the VCR to the EVR mode by transmitting the code
(F1) from the Jig RCU.
(4) Set the EVR address to (F2) by pressing the button of
the digit-key remote controller.
(5) Adjust with the channel buttons (+,–) on the VCR (or on
the remote controller) so that the level of the measuring
point (D) becomes the specified value (G).
(6) 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.)
Signal
(A)
• No signal
Mode
(B)
• Tuner
• EE
Equipment
(C)
• Frequency counter
Measuring point
(D1)
• IC1501 pin 26 [Demod board]
Short point
(D2)
• C1505(–) terminal [Demod board]
EVR mode
(F1)
• Jig RCU : Code “57”
EVR address
(F2)
• A : 21 (Press remote controller “2”
and “1” keys.)
Specified value
(G)
• 15.73 ± 0.1 kHz
Adjustment tool
(H)
• Jig RCU [PTU94023B]
• Digit-key remote controller
3.5.2 Stereo VCO
(1) Connect the short wire between the short point (D2) and
the GND (Ground).
(2) Connect the equipment (C) to the measuring point (D1).
(3) Set the VCR to the EVR mode by transmitting the code
(F1) from the Jig RCU.
(4) Set the EVR address to (F2) by pressing the button of
the digit-key remote controller.
(5) Adjust with the channel buttons (+,–) on the VCR (or on
the remote controller) so that the frequency of the meas-
uring point (D1) becomes the specified value (G).
(6) 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.)
(7) Disconnect the short wire between the short point (D2)
and the GND (Ground).
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.
Signal
(A1)
• Ext. input
(A2)
• Audio: No signal
(A3)
• Video: Color bar signal [NTSC]
Mode
(B1)
• S-VHS
(B2)
• REC (EP)
¥
PB
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)
• 600 ± 100 mVp-p
(G2)
• More than 400 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
S-VHS EP mode, 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.)
Fig. 3-4-1a Audio REC FM
600
ⴣ
100
mVp-p
V. rate
More than
400 mVp-p
3.4.1 Audio REC FM
