Just purchased and shipped to me. Box looked ok and was well packed.
Problem is frustratingly inconsistent. On certain cds it will play about 10s of the first song repeatedly, starting over each time.
On another cd it will reliably skip from about 20s into track 10 back to about 50s into track nine.
Sometimes it will take a few seconds to recognize the cd, and I hear something almost like static while it's spinning.
What I've done is clean the lens, cleaned and lubricated the rails. And make certain there is nothing mechanical that would be impeding the carriage as it has to move from one end to the other.
The white plastic gears appear to be in good condition and move freely.
Any ideas? I'm not an electrical engineer but I can figure out mechanical stuff.
Problem is frustratingly inconsistent. On certain cds it will play about 10s of the first song repeatedly, starting over each time.
On another cd it will reliably skip from about 20s into track 10 back to about 50s into track nine.
Sometimes it will take a few seconds to recognize the cd, and I hear something almost like static while it's spinning.
What I've done is clean the lens, cleaned and lubricated the rails. And make certain there is nothing mechanical that would be impeding the carriage as it has to move from one end to the other.
The white plastic gears appear to be in good condition and move freely.
Any ideas? I'm not an electrical engineer but I can figure out mechanical stuff.
Are you sure that it's the player? Many CDs will have problems after some use,
and different players will handle them differently. Try recording a "bad" one
using a computer drive. If it works, then the CD itself is probably ok.
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There's a tracking servo circuit that keeps the laser centered and focused.
If only a few of your CDs have problems on the new player,
that seems normal. Scratches tangential to the "grooves" are the worst.
CD - The Inside Story - Part 5 - Laser Tracking
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It generally works like this:
1/ The laser finds focus on the stationary disc.
2/ Only when focus is found does the disc run up to approximately the correct speed.
3/ With the disc spinning, the data is locked (compared to) a quartz crystal reference within the player. The spindle motor speed is then under servo control such that the data rate is constant... hence the reason the disc slows as it reaches the end.
4/ The reflected laser light falls onto a sensor with typically 6 cells, four grouped in the centre in the form of a square together with two side sensors. If the four centre cells are equally illuminated the laser is 'on track'.
5/ As the track progresses the servo moves the lens (not the sled at this point) however when the voltage across the lens X axis motor coil reaches a preset value then the sled is literally 'kicked' along a little to bring the error voltage back to zero. That is what tells the sled motor to move, it is the error voltage across the motor coil.
It is the side spot sensors that tell the servo to increase the coil X axis voltage (which happens when one sensor receives more light than the other), and as mentioned above, when the error voltage becomes to large for just the lens movement to accommodate the error then the sled is shuffled along a little.
1/ The laser finds focus on the stationary disc.
2/ Only when focus is found does the disc run up to approximately the correct speed.
3/ With the disc spinning, the data is locked (compared to) a quartz crystal reference within the player. The spindle motor speed is then under servo control such that the data rate is constant... hence the reason the disc slows as it reaches the end.
4/ The reflected laser light falls onto a sensor with typically 6 cells, four grouped in the centre in the form of a square together with two side sensors. If the four centre cells are equally illuminated the laser is 'on track'.
5/ As the track progresses the servo moves the lens (not the sled at this point) however when the voltage across the lens X axis motor coil reaches a preset value then the sled is literally 'kicked' along a little to bring the error voltage back to zero. That is what tells the sled motor to move, it is the error voltage across the motor coil.
It is the side spot sensors that tell the servo to increase the coil X axis voltage (which happens when one sensor receives more light than the other), and as mentioned above, when the error voltage becomes to large for just the lens movement to accommodate the error then the sled is shuffled along a little.
For minor scratches/cleaning, a CD scratch repair kit often works.
https://www.walmart.com/ip/Aleratec-DVD-CD-Disc-Repair-Plus/4858245
You can copy new CDs to your computer, and burn a new copy if/when the original fails.
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It would seem to me that the disc would spin FASTER as it moves to tracks closer to the center in order to maintain a constant data rate. Is the "first" track on the disc towards the center or towards the edge?
That all suggests that the recovered data is marginal and that the servos are working overtime to try and play the disc.
Ideally you need to look at the RF signal on a scope to gauge both the quality and amplitude.
Have a read at this... its pretty generic and applicable to most players.
http://www.diyaudio.com/forums/digital-source/226288-sony-cdp790-kss240-restoration-project.html
Ideally you need to look at the RF signal on a scope to gauge both the quality and amplitude.
Have a read at this... its pretty generic and applicable to most players.
http://www.diyaudio.com/forums/digital-source/226288-sony-cdp790-kss240-restoration-project.html
Week my friends it appears as if I've purchased an expensive paperweight.
I've neither the equipment it expertise to,take this any further. It continues to skip randomly from track to track and some tracks I can hear static that cycles with the disc spin.
I will need to find someone that can work on it and maybe go back into the market for another one.
I've neither the equipment it expertise to,take this any further. It continues to skip randomly from track to track and some tracks I can hear static that cycles with the disc spin.
I will need to find someone that can work on it and maybe go back into the market for another one.
There are no mechanical adjustments to make. All that has been factory adjusted... you never alter anything on the pickup (besides removing the 'shorting' blob of solder- if it has one- which is to protect the laser from static).
Provided the player hasn't been twiddled electrically and assuming the original pickup is at fault then you stand a fair to good chance of it all working.
There are ways and means to do some of the adjustments without a scope but I would suggest first seeing if the player is basically operational once a new pickup is fitted.
So no guarantees, but I don't think you have much to lose as long as you are careful.
Its only a few minutes work to swap a pickup over and it also gives a chance to clean the gears and give everything the once over.
Provided the player hasn't been twiddled electrically and assuming the original pickup is at fault then you stand a fair to good chance of it all working.
There are ways and means to do some of the adjustments without a scope but I would suggest first seeing if the player is basically operational once a new pickup is fitted.
So no guarantees, but I don't think you have much to lose as long as you are careful.
Its only a few minutes work to swap a pickup over and it also gives a chance to clean the gears and give everything the once over.
I replaced the pick up tonight and now it will not even read discs. Replacement was easy and I made certain that everything was put back together the right way. But to no avail.
When I load, "disc" flashes on the display, it spins briefly then quits. When I push play, the play button lights but the disc just sits.
Does this have a solder joint that I'm supposed to remove?
When I load, "disc" flashes on the display, it spins briefly then quits. When I push play, the play button lights but the disc just sits.
Does this have a solder joint that I'm supposed to remove?
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