JVC KDS788
Service Manual

KD-S788

Feed Section
Is the voltage output at IC521 pin "53" 5V or 0V? NO Is the wiring for IC521 (90) ~ (100) correct? NO YES NO YES YES Is 5V present at IC581 pin "11"? YES Check the vicinity of IC521. Is 6V or 2V present at IC581 "5" and "6"? NO Check IC581. Check the feed motor connection wiring. NO Check CD 9V and 5V.

Is 4V present at both sides of the feed motor? YES Check the feed motor.

Focus Section
When the lens is moving: NO Check the circuits in the vicinity of IC581 pins "15" ~ "18". YES YES Check the pickup and its connections.

4V
Does the S-search waveform appear at IC581 pins "17" and "18"?

Spindle Section
Is the disk rotated? YES YES Does the RF signal appear at TP1? YES Is the RF waveform at TP1 distorted? YES Proceed to the Tracking section NO Check the circuits in the vicinity of IC501 "19" ~ "24" or the pickup Check the spindle motor and its wiring. Check the vicinity of IC581. NO Is 4V present at IC581 pins "7" and "8" ? NO Is 4V present at IC521 pin "55" ? YES NO Check IC501 and IC521.

NO

Tracking Section
When the disc is rotated at first: YES Approx. 1.2 V Is the tracking error signal output at IC501 "12"? YES Check IC521. Check the circuit in the vicinity of IC501 pins "2" ~ "12". YES Check the pickup and its connections.

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