Hello, can anyone please help repairing a CLD-1750 that doesn't start spinning? Not even in test mode.
> Tray moves in and out flawlessly --> checked all tray and clamp location switches SW1, 2, 3, and S6 (Tray in), all good and signals reach the ASCB-board.
> The pickup moves toward the center of the CD (currently I have no access to LD's), attempts to focus but then returns to the "home" or "park" position. During this operation the LD/CD/CDV indicators on the display are flashing but the CD is not registered. Hence, pressing "Play" has no effect.
> Displacement of the pickup is between the positions where S4 (Park1) is opening and S5 (Outer) is opening. Both signals also reach the PC-board.
> The tracking servo is active (moves up and down as expected) and can be activated in test mode.
> The laser is powered and voltage drop across R873 (10 Ohm) is 660mV --> 66mA of current.
> At the LD connection of the pickup I measure 1,85V. The laser is clearly visible using my cell phone camera.
> The photo-diode output (PD connection) goes from -5,1V (laser off) to -3,8V when the laser is on.
> The spindle motor is OK. Could make it run with an external supply or by inserting a 1,8kOhm resistor between Accel and XAccel (pin 1 and 2 of CN102). Consequently the power transistors are ok.
> As the Drive 1 and Drive 2 signals remain at 0V all the time it seems either a defect or a missing condition prevent powering-up the spindle motor.
> In test mode all of the above could be confirmed but it didn't help to resolve the issue.
> The unit never enters play-mode so I was unable to check any signals (e.g. RF output of the pick-up) even if I forced the spindle to run. Not focused?

Kind regards.

All the DC levels can be fine but if the laser does not return pulse the unit will act like no disc is installed and the spindle will not be initiated.

You have to put an oscilloscope on the RF test point. When the tray closes you'll see the laser move to the LD position and the lens moves up to see if the laser can return a reflection and if it doesn't the laser moves into the CD position and the laser lens moves up again. At that time you should see a short single pulse of amplitude on the RF test point. If there is no pulse or just a small pulse that signals no disc and the unit will not spin the spindle as it thinks no disc is installed. Usually a weak laser.

Hi Krabahr, thanx for your advice. On the RF test pin, with the sensitivity set to 10mV I can only see a very shallow pulse, just enough to distinguish from the noise. As you indicated I guess the laser power is too low. Any other suggestions apart from replacing the pick-up? Do you know of any reliable vendors for this part? Your help will be appreciated.

I do not have any contacts for lasers, Pioneer quit supporting them years ago. You can do to the Hardware PDF manuals sections and you can get the details for your unit.