Hey everyone!
I was given an NEC CD-705 player that won't read discs. It tries to read the disc, spins it around for a while but then spits it right back out. Does it with every disc. I've tried newer and older discs, originals and CD-Rs, high and low reflectivity but this guy's having none of it.
Took the lid of and observed the action with no disc in. It uses a photo diode detector so it's easy to trick it into seeing a disk. The pickup moves to the front and backs up a little, motor runs, lens moves in and out, the pickup then drives forward, tries again, drives forward, tries again, etc... until it gives up and ejects the disk.
I tried cleaning the lens, re-capped the laser PSU board and tried adjusting the two trimmers on the laser PSU board but no luck. It's a 2nd gen player and uses a Toshiba OPH-32 pickup which is unfortunately no longer available. I don't know how strong the laser is but I don't remember it being visible to the naked eye. Looking at the laser with a camera, there is a blue-ish-purple laser dot visible but it's not super strong.
There doesn't seem to be a service manual available for this unit.
Anyone have any ideas? I work on a lot of professional and home audio equipment but I've not worked on many CD players apart from easy stuff like lens cleaning, belt replacement, etc...
How should I go about testing it? How should the RF, laser power, etc be checked?
It looks like a pretty nice unit and it's visually in immaculate condition, would make a great addition to my workshop hi-fi stack.
Here's a video of what it does:
YouTube
I was given an NEC CD-705 player that won't read discs. It tries to read the disc, spins it around for a while but then spits it right back out. Does it with every disc. I've tried newer and older discs, originals and CD-Rs, high and low reflectivity but this guy's having none of it.
Took the lid of and observed the action with no disc in. It uses a photo diode detector so it's easy to trick it into seeing a disk. The pickup moves to the front and backs up a little, motor runs, lens moves in and out, the pickup then drives forward, tries again, drives forward, tries again, etc... until it gives up and ejects the disk.
I tried cleaning the lens, re-capped the laser PSU board and tried adjusting the two trimmers on the laser PSU board but no luck. It's a 2nd gen player and uses a Toshiba OPH-32 pickup which is unfortunately no longer available. I don't know how strong the laser is but I don't remember it being visible to the naked eye. Looking at the laser with a camera, there is a blue-ish-purple laser dot visible but it's not super strong.
There doesn't seem to be a service manual available for this unit.
Anyone have any ideas? I work on a lot of professional and home audio equipment but I've not worked on many CD players apart from easy stuff like lens cleaning, belt replacement, etc...
How should I go about testing it? How should the RF, laser power, etc be checked?
It looks like a pretty nice unit and it's visually in immaculate condition, would make a great addition to my workshop hi-fi stack.
Here's a video of what it does:
YouTube
Altering the trimmers without knowing what they do could be a fatal mistake tbh...
The only way to check the laser in a player that is non functional is to use a proper laser power meter that will measure the optical power of the beam.
If it tries to read a disc then you could use a scope and look at the RF signal and try a gauge the amplitude. Typically around 1.2v peak/peak would be a fairly common ball park figure. Should be possible to locate an RF test point by looking at the chipset and/or just trial and error.
Also make sure the platter height looks about right, sometime the platter can take a hit and be knocked down the motor shaft.
On balance its probably not looking good... but you never know.
The only way to check the laser in a player that is non functional is to use a proper laser power meter that will measure the optical power of the beam.
If it tries to read a disc then you could use a scope and look at the RF signal and try a gauge the amplitude. Typically around 1.2v peak/peak would be a fairly common ball park figure. Should be possible to locate an RF test point by looking at the chipset and/or just trial and error.
Also make sure the platter height looks about right, sometime the platter can take a hit and be knocked down the motor shaft.
On balance its probably not looking good... but you never know.
I saw some videos of laser power adjustment where the trimpot on the laser was slightly adjusted. So I marked the original positions and tried adjusting both pots either way about a millimeter like in the videos but it changed nothing. So I set them back to their original position.