It would then be the 10Ohm resistor. I am familiar with Technics CD players, where usually a 12Ohm resistor is used. Anyway, I would also suggest to check the specifications of the LD, it list the minimum current required, the maximum and some average value. This would be a good start.Thanks. According to schematics, there are 2 resistors, one of 2k2, and one of 10 ohms, next to the base, respectively the emitter of the transistor in the APC circuit (if the schematics presented here is correct).
I mus appologise to all of you, I'm not trying to discover the wheel, just doing some practice.
Thanks in advance.
Still, the goal would be to get the laser beam in the center of the diode array - and that is the tricky part.
Attached details might give you some idea about how delicate this is. Therefore, an alignment tool, some measuring electronics and oscilloscope is needed.
(p.s. the picture shows the optical pickup from a Technics SL-P2 )
Attachments
@ASAMS Thanks for reply. As I have only a PC based osciloscope and some DMM, I will not be able to properly setup the laser. Regarding laser diode, the operating current is 52-70 mA, according to datasheet. Most laser pickups show ~60 mA on the lable. Next I will look for a laser power meter.
@cupitza I have not experienced any issue not having such a laser power meter. The 'RF' signal and the laser current would normally be sufficient.
I also have only an USB scope, but that works quite well.
Did you actually measure the 'RF' signal already? You may see a kind of S-shape response when the pickup/lens tries to focus (= moves up and down).
As this stage, the electronics tries to detect the if the signal contains also a higher frequency (= refection from 'pits'). That most likely does not happen here, but looking at the 'RF' might give at least some idea.
I also have only an USB scope, but that works quite well.
Did you actually measure the 'RF' signal already? You may see a kind of S-shape response when the pickup/lens tries to focus (= moves up and down).
As this stage, the electronics tries to detect the if the signal contains also a higher frequency (= refection from 'pits'). That most likely does not happen here, but looking at the 'RF' might give at least some idea.
@ASAMS The disc doesn't spin when inserted into the player, so I can't measure the RF signal, even though the laser beam is very visible and the laser pickup is testing it. This is one of my questions that need an answer: why disk doesn't spin? The caps on the BSL board are replaced and it works with other laser pickup.
@cupitza , of course you would see some signal here. If there isn't any, the light beam would not even be close. You will certainly NOT SEE the typical eye pattern, if this was present, the disc was already detected. You may see something like this - and even in this example, there is already some indication that the 'pits' are seen (please note the scale: 20ms - these are the attempts of the lens to focus) .
@ManoloMos Thanks. I already know how it works, but I don't have equipment to adjust diode array. This is kind of lottery, if you don't have properly equipment.
I have seen your works and they are impressive. I'm not an electronics technician, but I graduated in engineering. I have knowledge of electricity and some electronics. What I'm doing now is an exercise.
I have seen your works and they are impressive. I'm not an electronics technician, but I graduated in engineering. I have knowledge of electricity and some electronics. What I'm doing now is an exercise.
Instrumentation and equipment are essential.
A mirror, a support for the laser pickup, some op-amps, low frequency oscillator, and a bit of practice.
And yes, a lottery, if you replace the laser diode is tiny posibility that the laser pickup works again, the posibility is low, but it is not zero.
Maybe, if you try to adjust the tiny torx screws that adjust the laser pickup angle, could work, but, I'd not try, because the risk don't worth.
A mirror, a support for the laser pickup, some op-amps, low frequency oscillator, and a bit of practice.
And yes, a lottery, if you replace the laser diode is tiny posibility that the laser pickup works again, the posibility is low, but it is not zero.
Maybe, if you try to adjust the tiny torx screws that adjust the laser pickup angle, could work, but, I'd not try, because the risk don't worth.
@cupitza : I am not familiar with this pickup, but what just came into my mind when reading ManoloMos' comment, there is a little chance that maybe only the angle of the lens needs adjustment. If not done, take note of its current position (measuring distances) and maybe give it a try. Apparently, this CD player seems to have a kind of test function you could use (like the test above) where it may only try to focus.