Sanyo HV-DX4EV, Service Manual

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7
2. SYSTEM CIRCUIT
TROUBLESHOOTING
6
TROUBLESHOOTING
Noise appears on the
playback screen.
Is noise diminished by tracking
adjustment.
Noise band is trembled up and
down?
Re-adjust PATH.
Is the height of CTL HEAD normal?
No dust?
Is there problem in CTL Input
circuit and amplifier.
YES
NO
NO
NO
Is there CTL pulse at IC501
pin#97?
Check IC501.
Noise appears on the screen even
though changing tape.
Re-adjust the height of AC HEAD.
Remove the dust.
Check C510,R545~R547
IC 501 pin #91, 92, 98.
NO
Re-adjust PATH.
B-1. Bad playback quality (1)
YES
YES
YES
YES
No LED display.
Is 5V obtained at IC701
pin #9, 25?
Oscillation at IC701pin #1?
Specific GRID/SEG doesn t function.
Check R588, D857, L503, L860
Exchange IC701.
Check IC 701 pin #22~24, 27,
28, 30, 31.
Check IC 701 pin #10~12, 14~21.
NO
YES
YES
NO
NO
GRID output at PORT of IC701?
YES
SEG output at PORT of IC701?
Exchange IC701.
YES
A. LED DISPLAY
NO
Noise appears on the Full
playback screen.
Are SW pulse and HA SW normal?
Recheck step B-1
(Bad playback quallty (1)).
Check HEAD AMP connector
and HEAD.
YES
YES
NO
NO
ENVE Wave at PT01 pin #4?
Check VIDEO circuit.
Are there SW, HA SW pulse at
IC501 pin #16, 18?
Check PCB Pattern.
Check IC501.
B-2. Bad playback quality (2)
YES
NO
YES