I'm looking at a DVD player with an odd problem in the tracking actuator se rvo. When a DVD is loaded, both original or recorded, it focuses, spins and positions the lens fine - up to this point the tracking actuator keeps the lens centered. Then suddently the lens moves to one end of the tracking ac tuator range, a click is heard as the actuator hits a plastic stop and the sled does not move. This situation lasts about two seconds until it retries by moving back and forth the sled, refocusing and reactivating the trackin g servo - the same repeats. After two tries a disk spin down and spin up ha ppens and the read is attempted two times more before a disk error message pops up.
This tracking failure happens almost always, but occasionally it will load and play the disk for a while but sooner or later the lens clicks again. I' ve seen it click, then recover and continue to play. It does not respond to mechanical stress to the board. I suspect this failure happens more often at higher spindle speeds, that may explain why original DVD are harder to g et to load than DVD-R. I have double-ckecked the motor for shorts in windin gs or rotary contacts problems and could not find anything strange.
With CDs the behaviour is different, the tracking actuator does not click t o one end but it has some difficulties keeping the tracking stable and the data readout error free, with occasional sled repositionings as if it had s ome trouble reading the data. These sympthoms happen more at the beginning and mid way tracks and never at the outmost tracks. I relate that again to the lower spindle speed in these tracks.
The player is a Supratech vision Artemis (DVD player with USB, card reader and DVB-T tuner) and has board SUNPLUS 8202A with SPHE8281A chip (256 pin v ersion) and a Sanyo HD850 pickup. The SPHE8281A outputs the tracking actuat or signal on pin 42 labeled DATEO and that is input to the CD5888CB (actuat or and motor driver) through a 68K resistor. Monitoring this signal reveals a voltage of 1.5 to 1.7V during normal operation and jumps to 2.5 to 3.0V when the click occurs. There are three more pins on the SPHE8281A related t o tracking, the names are referenced in the datasheet but no more details a re provided: pin 34: TEO (Tracking error signal output) pin 35: TEOLP (TEO low pass?) pin 26: V165 (Reference DC BIAS voltage)
The datasheet refers to a servo datasheet for additional information that I could not find. Signals TEO and TEOLP follow the same behaviour as DATEO, and V165 is always 1.6V. TEO has a 330p capacitor to ground and TEOLP a 100 nF one. I've checked all servo supplies and grounds and ruled out the power supply by powering it with a PC power supply. The board runs off a single
5V supply and has its own 3.3 and 1.8V regulators. I've checked all capacit ors for ESR.Thank you in advance for your replies.