Sony DVP-S300, Training Manual

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4. Sometimes when a chip select signal is missing, the IC it points to is
actually not defective. Usually a communications failure between IC202
and the remaining ICs on the serial or parallel bus is within the MB-82/
85 board. This could be caused by lack of power to non-communicat-
ing IC or it could just be defective.
Another possibility is that one of the programs in that IC cannot finish
because of a mechanical defect, so there is no acknowledgement
signal to complete the communications. For example, if IC701 is send-
ing a sled drive move signal but the IC fails to receive a sled home
indication after a fixed time (“time out”), IC701 will not acknowledge
IC202.
Syscon IC202 will tell IC201 to shut down. In this failure example sled
driver IC802 is defective so the sled cannot move. Since IC701 is the
last chip in the chain, all the chip select signals are present. If the unit
shuts down with all the chip select pulses present, IC701 is not send-
ing the final acknowledgment signal so the problem is at IC701 or its
slave ICs (IC801 or IC802). In this case, use the test mode to manu-
ally drive the focus, tracking and sled, tilt motors.
5. Inspect IC205/6 and check to see if this IC is one of the few units that
needs to be upgraded in the service bulletin # 61 for a 0.5-second lip
sync delay. This upgrade has no relation to the green to red power
light symptom.