Open the cover of electric machine, radial head back and forth in the small scope, the lens of vertical lifting 5 times, normal search focus. In order to facilitate the observation of the laser tray to extend with a flat screwdriver insert D shaped hole on the left side of the tray in the right toggle guide rail bracket slot limit plastic sheet, the pallet is unloaded. Point press switch button, to be a tray telescopic gear clockwise rotation, press the tray in place of micro switch, gear to stop, the head is to enter the initial process. In a wide range of 30cm, a bright red light can be observed in the objective lens. See objective lens surface with a small amount of stains, with a brush dipped in distilled water clean, with a cotton suction to remove excess water, into the disc test machine, invalid. Using the meter R * 1 measuring range of spindle motor at both ends (grass green, yellow), motor running smoothly, the motor is normal. Due to the unaided eye laser intensity is not accurate, with 500 million in R * 1K range of the table with infrared receiving diode (see the 40, 1996 issue of this version of the article) indirect detection of laser intensity, pointers from 500K ohm dropped to about 25K. Test retest laser voltage across the diode (bald rear side surface of the capacitor voltage measurement) 1.83V and normal. Try to adjust the APC circuit on the VR, then the voltage is 1.88V, the test is still invalid.

According to the working principle of spindle motor start know, bald optical cavity in photosensitive receiving tube will change the disc reflection to the pit signal into electrical signals, amplified by preamplifier TDA1300 shaping, from {9} output RF signal into the foot of the CAA7372{15} digital processing, from on {33} feet, {34} output pin, the RC filter network into DC signal applied to a TDA7073{6} foot control terminal, {7} feet for the end of the reference voltage, by driven processing from {9} feet, {12} output driving voltage, the spindle motor electric start. Remove movement, on the frame of the spindle disc placed on the disc (don't pallets, lest the telescopic movement of the tray to hinder the signal test) and by hand to head together with the vehicle head frame of the sliding support pushed to the working position, and automatic closing of the loader holding a disc. Flip the circuit board to the top, so that the head into the initial program, TDA7073{6}, {7} pin voltage is 0V (normal 0.3V), there is no driving voltage. CAA7372{33}, {34} pin voltage, 0V (normal 4.2V) measured TDA1300{9} pin voltage 0.4V (when output RF signal normal voltage should be 1.5V) and head rest for 0.35v (normal), visible {9} feet without an output RF signal measurement. Check TDA1300 peripheral 6 components as well as the foot static, dynamic voltage are no problem, flexible flat line connection without breaking, the judge is still in the head!

In order to find out the root cause of the failure of the determination of the operation of the bald. Press and hold the head left, with a needle pick to lens on both sides of the latex, remove the lens see 45 degrees polarizing beam splitting mirror positioning firm, mirror has a small amount of dust, with a cotton swab to clean after reduction, test machine is still valid. And a few months to find a similar machine for comparison, the measured data are basically the same. I have seen in 1999 newspaper section 23 of the said Philips head has three characteristics: (1) laser tube before and after aging of the laser intensity is not obvious; (2) after aging of the laser tube rarely pick the dish, but more is simply not read dish; (3) laser tube after aging regulation APC power potential is largely ineffective. Seems to be true! But I still decided to do a reason to explore. I cut off the line of laser tube and APC in Q3c between the measured laser tube resistance is 43K omega (normal value as the 15K ohms to 25K), has indeed aging undoubtedly. So the light sensitive receiver tube and how it? I the following test: the commercially available laser pen alignment lens hole, measuring with installed in the optical cavity of the photosensitive tube resistance changes, results in positive and negative resistance infinity (do not rule out the photosensitive tube did not receive the signal light), doubt the photosensitive tube failure. Due to PHILPS's head is more difficult to repair, replace the new head, the fault that is ruled out, they will not do further exploration. The Greek line repair this head more experience and know-how master generous with your criticism.