Hi Andy,
Any change in height will throw off the azimuth and possibly focus (if severe) of the laser to the disc. But the wobbling of the clamper suggests you have something under one side of the disc that will make things worse as the laser tracks to the outside.
The noise you describe is expected when you have problems like this, it's just severe digital errors, that's all.
So clean the disc table and make sure it's flat with no debris - same for the CD in the area where it is clamped. What you really need is an oscilloscope. If cleaning doesn't work, then you should enlist the help of a skilled electronics technician. We actually receive training on these things. Even if you get it functioning, you have no idea if it is working properly or if there are other issues. A good technician can be your best friend.
-Chris
Any change in height will throw off the azimuth and possibly focus (if severe) of the laser to the disc. But the wobbling of the clamper suggests you have something under one side of the disc that will make things worse as the laser tracks to the outside.
The noise you describe is expected when you have problems like this, it's just severe digital errors, that's all.
So clean the disc table and make sure it's flat with no debris - same for the CD in the area where it is clamped. What you really need is an oscilloscope. If cleaning doesn't work, then you should enlist the help of a skilled electronics technician. We actually receive training on these things. Even if you get it functioning, you have no idea if it is working properly or if there are other issues. A good technician can be your best friend.
-Chris
Anatech is spot on with his train of thought on this and ideally a quick check with a scope would be the first port of call. The reason CD's were designed to play from the middle outwards was for the very reason that focus and tracking is more easily achieved and stable at the centre region compared to the disc edge.
If you look at the spinning disc edge on (so look in the horizontal plane) there should be virtually no detectable up/down variation as the disc rotates. By looking edge on you can also see the lens and if it is bobbing up and down with each revolution then that means it is constantly focusing on a changing disc height. The further out toward the edge the laser is and the more pronounced the effect.
I'm going to say on the disc clamp that if it is eccentric as it spins then it may still be OK as these things just flop onto the disc and clamp magnetically but they often do not centre exactly. That is not usually an issue. I can't just recall what these were like from memory for that.
Given how troublesome the KSS240 could be and given how cheap replacements are it might be worth trying a new one. They are one of the pickups where many say the replacements are OK quality wise and they should be plug and play, at least to get a working player. Proper optimisation would need a scope but that said our techs fitted these by the bucket load back in the day.
If you look at the spinning disc edge on (so look in the horizontal plane) there should be virtually no detectable up/down variation as the disc rotates. By looking edge on you can also see the lens and if it is bobbing up and down with each revolution then that means it is constantly focusing on a changing disc height. The further out toward the edge the laser is and the more pronounced the effect.
I'm going to say on the disc clamp that if it is eccentric as it spins then it may still be OK as these things just flop onto the disc and clamp magnetically but they often do not centre exactly. That is not usually an issue. I can't just recall what these were like from memory for that.
Given how troublesome the KSS240 could be and given how cheap replacements are it might be worth trying a new one. They are one of the pickups where many say the replacements are OK quality wise and they should be plug and play, at least to get a working player. Proper optimisation would need a scope but that said our techs fitted these by the bucket load back in the day.
Thanks Anatech and Mooly.
The disk and clamp appear to be clean with no defects, the CD's are also clean.
When the disc is spinning I do not see any noticeable up and down motion. I couldn't really tell if the lens was having trouble keeping focus. As the final tracks of a disc were playing I thought I could see some up and down motion of the lens but not what I I would call a bobbing motion. Then again I don't know how much motion is too much.
I could try a replacement KSS240. or find a second hand donor player at swap the whole mechanism.
My first choice is to find a good tech to help me unfortunately no luck ,so if anybody has any recommendations in the Toronto/GTA area I would appreciate it.
The disk and clamp appear to be clean with no defects, the CD's are also clean.
When the disc is spinning I do not see any noticeable up and down motion. I couldn't really tell if the lens was having trouble keeping focus. As the final tracks of a disc were playing I thought I could see some up and down motion of the lens but not what I I would call a bobbing motion. Then again I don't know how much motion is too much.
I could try a replacement KSS240. or find a second hand donor player at swap the whole mechanism.
My first choice is to find a good tech to help me unfortunately no luck ,so if anybody has any recommendations in the Toronto/GTA area I would appreciate it.
A donor machine/mechanism is quite likely to have issues really. Only just detectable lens movement up/down is probably OK although ideally there should be none. The up/down is the lens keeping the same position from the disc surface. So if the lens seems to move say -/+ 1 millimetre then it means the disc at that point is running out of true in the vertical plane by -/+1 millimetre.
The thing with CD players (and all optical systems) is that a 100% good player can usually withstand a large error or problem in one area. As things deteriorate it all becomes more critical as if running on a knife edge.
Without testing it all at a higher level with a scope for example all we can say is that a new KSS240 stands a pretty good chance of fixing it (but not guaranteed of course).
The thing with CD players (and all optical systems) is that a 100% good player can usually withstand a large error or problem in one area. As things deteriorate it all becomes more critical as if running on a knife edge.
Without testing it all at a higher level with a scope for example all we can say is that a new KSS240 stands a pretty good chance of fixing it (but not guaranteed of course).
This may be a foolish question, is it worth trying to repair the player without a schematic diagram?
I did find a shop to check the machine. They told me only 4 caps of 32 are within spec, also 3 overheated resistors on the main board.
I was given what i think is a fair price to make repairs with a good chance of success based on their experience, but without a schematic diagram, obviously no guarantees.
I hate to get rid of this player, then again noting lasts forever.
I did find a shop to check the machine. They told me only 4 caps of 32 are within spec, also 3 overheated resistors on the main board.
I was given what i think is a fair price to make repairs with a good chance of success based on their experience, but without a schematic diagram, obviously no guarantees.
I hate to get rid of this player, then again noting lasts forever.
check out post #8 under
https://www.diyaudio.com/community/threads/laser-pickup-failure-modes.10506/
https://www.diyaudio.com/community/threads/laser-pickup-failure-modes.10506/
Found a Sony CDP-690 in very good condition at the local thrift shop, with dual AD1860 18-bit DACs instead of the later CXD2552 1-bit pulse DAC. The tray was having trouble due to an old belt, so I cleaned it and seems fine now. Although my CDP-X111ES (AKA CDP-791) is not working at the moment due to transport issues (meaning I can't do a proper A/B comparison right now) I think the multibit AD1860s sound better than the newer 1-bit converter, something mentioned earlier in the thread.
I also installed a few Panasonic FR electrolytics in the power supply and a DIP socket to replace the RC4558 output op amp, which is now ADA4627-1; the 4558 contributes to a "mid-fi" sound, IMO. I compared the headphone output of the modded CDP-690 to my modded TC Impact Twin via optical S/PDIF and thought the CDP-690 sounded better... more alive and dynamic somehow. Not sure how much is due to converters and/or analog stages. Curiously, an online search has turned up three different revisions of the CDP-690: one with AD1860s, one with CXD2552, and another with only one pair of analog outputs (instead of a two sets, one fixed, one variable with remote control).
Would like to compare both with my Luxman DZ-112, but it also has transport issues which I haven't been able to resolve. After I modded the DZ-112, I thought the PCM1701s and analog section sounded surprisingly nice, and noticeably better than the X111ES. Suspect that its laser might be on the way out, as it was finicky reading discs when I got it and the fluorscent display shows signs of fading from years of use. Would be nice to get it working again.
The CDP-690 is somewhat sensitive to knocks and disc quality, but seems fine with a clean disc. It even played an 80 minute overburned CD-R without issue. The display is clear and bright and the unit looks like it was not used much over the past three decades. Perhaps at some point I will hook it up to the oscilloscope and check the eye pattern. However, for now, I'm just enjoying listening to CDs again, as it is my only working player at the moment....
I also installed a few Panasonic FR electrolytics in the power supply and a DIP socket to replace the RC4558 output op amp, which is now ADA4627-1; the 4558 contributes to a "mid-fi" sound, IMO. I compared the headphone output of the modded CDP-690 to my modded TC Impact Twin via optical S/PDIF and thought the CDP-690 sounded better... more alive and dynamic somehow. Not sure how much is due to converters and/or analog stages. Curiously, an online search has turned up three different revisions of the CDP-690: one with AD1860s, one with CXD2552, and another with only one pair of analog outputs (instead of a two sets, one fixed, one variable with remote control).
Would like to compare both with my Luxman DZ-112, but it also has transport issues which I haven't been able to resolve. After I modded the DZ-112, I thought the PCM1701s and analog section sounded surprisingly nice, and noticeably better than the X111ES. Suspect that its laser might be on the way out, as it was finicky reading discs when I got it and the fluorscent display shows signs of fading from years of use. Would be nice to get it working again.
The CDP-690 is somewhat sensitive to knocks and disc quality, but seems fine with a clean disc. It even played an 80 minute overburned CD-R without issue. The display is clear and bright and the unit looks like it was not used much over the past three decades. Perhaps at some point I will hook it up to the oscilloscope and check the eye pattern. However, for now, I'm just enjoying listening to CDs again, as it is my only working player at the moment....
Hi 12Bass,
The PCM1701 should be related to the PCM1702, which is a co-linear DAC. Anything I have ever heard using a PCM1702 or PCM1704 sounds great as long as the audio was done properly. My machine (Denon DCD-S10) uses a pair of PCM1702 per channel. It so far kills everything it has been compared to. These sounded far superior to any 1-bit (Mash) type DAC.
Your transport probably needs to be cleaned and aligned. It is also possible you have worn disc motor bearings and a near end of life laser. I have serviced CD players since their introduction and am extremely familiar with them. I was warranty for Luxman among many others.
Anyway, step one to assess a CD player is to look at the eye pattern (RF pattern). You need an oscilloscope that can sweep 0.5 uS/div, normally 0.5 V/div should display a clear pattern well enough. Digital scopes are very poor at this, don't even try. I bought a Keysight MSOX3104T , and my analogue scopes are better. The Keysight was the best DSO for looking at eye patterns I could (barely) afford.
You also need experience to determine what a CD player needs. Don't try and do this yourself following helpful suggestions from people who don't really know. If you can't do this, find a very good AUDIO technician close to you and have them deal with them. Once rebuilt the transports are like new, so well worth doing.
-Chris
The PCM1701 should be related to the PCM1702, which is a co-linear DAC. Anything I have ever heard using a PCM1702 or PCM1704 sounds great as long as the audio was done properly. My machine (Denon DCD-S10) uses a pair of PCM1702 per channel. It so far kills everything it has been compared to. These sounded far superior to any 1-bit (Mash) type DAC.
Your transport probably needs to be cleaned and aligned. It is also possible you have worn disc motor bearings and a near end of life laser. I have serviced CD players since their introduction and am extremely familiar with them. I was warranty for Luxman among many others.
Anyway, step one to assess a CD player is to look at the eye pattern (RF pattern). You need an oscilloscope that can sweep 0.5 uS/div, normally 0.5 V/div should display a clear pattern well enough. Digital scopes are very poor at this, don't even try. I bought a Keysight MSOX3104T , and my analogue scopes are better. The Keysight was the best DSO for looking at eye patterns I could (barely) afford.
You also need experience to determine what a CD player needs. Don't try and do this yourself following helpful suggestions from people who don't really know. If you can't do this, find a very good AUDIO technician close to you and have them deal with them. Once rebuilt the transports are like new, so well worth doing.
-Chris
Hello Mooly, I'm asking you about the sled motor, I have an old Sony CDP M11, with a KSS240 laser. It presents jumps (many), the voltage of the RF signal was about 0.5Vpp (20MHZ oscilloscope), I found that the sled had friction in a gear against a deformed plastic, I solved this, cleaned and lubricated again, increased the amplitude of the signal by modifying the laser power setting to 0.8/0.9Vpp (1.2Vpp -0.4V suggested by the service manual). Result, it reads original CDs correctly (not so much with CDRs) but sometimes it skips. I have monitored the voltage of the sled motor and it oscillates between positive and negative values between approximately -1.3 and 1.3V, it does so slowly. I understand that I already start with a laser, perhaps a little exhausted, but I would like to know based on your experience if the values recorded in the sled motor are correct or there may still be something wrong there. Thank you so muchPleased you found it all useful
First thing has to be to clean the lens. It should look bright and shiny with a bluey tinge under a stong torch light. I know ISO (IPA) seems to get a universal recommend as a cleaner but its something I would never use on optics tbh. In the early days Sony even issued a warning to that affect saying that ISO could damage (the then newly introduced) "coated optics". Camera lens cleaner perhaps or just warm water with a single drop of detergent mixed in.
I doubt whether the sled is sticking tbh but that said you have to consider the possibilty. Monitoring the voltage across the sled motor in playback is a good clue. If it suddenly starts to rise its a good indication the sled has stuck. The voltage will keep rising until the motor overcomes the friction and the sled jerks forward.
Most likely is a faulty pickup. The KSS240 was notorious for giving trouble. A replacement should work straight off and is easy to fit.
Sled motors tend to shuffle along as the disc plays and the spindle of the motor can almost look to oscillate a little back and forward as it does this. Of course that is what those + and - voltages would do. So that's normal and I those voltage sound reasonable. If you take the sled motor out you give it a quick whizz on a 9 volt battery (isolate the motor electrically as well as mechanically first) and that can help clean up the commutator.
Usually if there is a sled problem the voltage across the motor keeps on increasing until the friction is overcome and the whole sled jolts forward usually giving a 'skip'. If that is not happening then it could well be a faulty pickup.
Usually if there is a sled problem the voltage across the motor keeps on increasing until the friction is overcome and the whole sled jolts forward usually giving a 'skip'. If that is not happening then it could well be a faulty pickup.
If lubrication is wrong, same observation I had often make and desribe even here:
https://audiokarma.org/forums/index.php?threads/philips-cdm12-sled-rail-lubrication.974511/
Lubrication is simple, and it varies for the materials involved. I have different lubrication types for different slide rail / head combinations. Obviously if the rails run dry, it will stick. Harder to spot is bearing wear which will cause the same thing, normally not as severe with metal on metal - unless there are no bearings. Plastic on metal is bad news, that will wear long before the laser has problems.
Ceramic slide rails are a real problem. Plastic heads are worse.
Cheap knock-off heads normally do not have sleeve bearings for the slide rail. If you head has no bearings ... it has a limited life span.
The fact remains, if the head assy gets stuck, the sled motor drive will reverse polarity. If it is free, the drive voltage will rise, drop quickly but not reverse. It is that simple. The sled drive is typically a low pass filtered signal from the tracking coil in the laser head. So, a DC average in simple terms. They may inject a sine on that signal to keep the brushes in motion. That helps keep communtators clean in these motors.
tiefbassuebertr,
Don't look for intelligent information at AudioKarma. It seldom exists.
Ceramic slide rails are a real problem. Plastic heads are worse.
Cheap knock-off heads normally do not have sleeve bearings for the slide rail. If you head has no bearings ... it has a limited life span.
The fact remains, if the head assy gets stuck, the sled motor drive will reverse polarity. If it is free, the drive voltage will rise, drop quickly but not reverse. It is that simple. The sled drive is typically a low pass filtered signal from the tracking coil in the laser head. So, a DC average in simple terms. They may inject a sine on that signal to keep the brushes in motion. That helps keep communtators clean in these motors.
tiefbassuebertr,
Don't look for intelligent information at AudioKarma. It seldom exists.
Hi to all,
I've read this thread and other similar, but my Sony CDP-H3600 (equipped with KSS-240A) won't work.
Months ago starts to jump seconds, skip tracks random. Then I clean lens with ethyl alcohol, it starts to work (with some errors) but 2 months ago stop to run spindle motor.
I've tried to clean again lens, to change focus trim, but motor spindle won't run.
I've tried to buy the KSS-240A, but on the web I've read that this one for 10/15 € are fake.
What can I do else ?
I've multimeter but no scope (broken).
Thanks
I've read this thread and other similar, but my Sony CDP-H3600 (equipped with KSS-240A) won't work.
Months ago starts to jump seconds, skip tracks random. Then I clean lens with ethyl alcohol, it starts to work (with some errors) but 2 months ago stop to run spindle motor.
I've tried to clean again lens, to change focus trim, but motor spindle won't run.
I've tried to buy the KSS-240A, but on the web I've read that this one for 10/15 € are fake.
What can I do else ?
I've multimeter but no scope (broken).
Thanks
Well, before touching any adjustments, you needed to find out what the fault was. If you do not have an oscilloscope, stop. Either trash it or send it to a good technician, that's up to you. As soon as you begin twisting controls, give up right there, now you are in trouble.
The unit will not spin the disc if it can't get a focus lock. It also needs to know the head went to home position. Honestly, I was trained by the factories how to repair CD players. Some techs weren't very good at it. This isn't something the average person can fix, not properly. If you manage to get it running, it probably still isn't working correctly.
I can't understand why readers actually believe trained technicians aren't highly trained, because the good ones really are. You're trying to do the job of a trained professional - without any training or equipment.
The unit will not spin the disc if it can't get a focus lock. It also needs to know the head went to home position. Honestly, I was trained by the factories how to repair CD players. Some techs weren't very good at it. This isn't something the average person can fix, not properly. If you manage to get it running, it probably still isn't working correctly.
I can't understand why readers actually believe trained technicians aren't highly trained, because the good ones really are. You're trying to do the job of a trained professional - without any training or equipment.
Sorry, maybe I was wrong to do what people on other webpages suggested me to do.
Only in these last days I've found this forum :-( So I've already made changes on trimmers... but made a mark and took pictures of trimmers, to re-set them to 'original' position.
I was encouraged to try to do by myself reading what other user did on this thread.
Anatech, what do you suggest me to do / to check now?
I'm quite able in electronics/soldering.
Thanks in advance
Only in these last days I've found this forum :-( So I've already made changes on trimmers... but made a mark and took pictures of trimmers, to re-set them to 'original' position.
I was encouraged to try to do by myself reading what other user did on this thread.
Anatech, what do you suggest me to do / to check now?
I'm quite able in electronics/soldering.
Thanks in advance
Hi elpossa,
Well, there is the root problem. At least you figured it out now. Most people who post on how to repair don't actually know, or aren't good techs themselves.
Okay, trimmers back in position. At least with the KSS-240A there are fewer board adjustments.
Two quick checks. Run the head out manually by turning the gear - do not force anything. Without a CD inserted, turn the unit on. The tray should close and the head should run to the centre, then back out slightly. Then you should see the lens go up and down 2 1/2 to 3 times.
Tell us what happens please.
Well, there is the root problem. At least you figured it out now. Most people who post on how to repair don't actually know, or aren't good techs themselves.
Okay, trimmers back in position. At least with the KSS-240A there are fewer board adjustments.
Two quick checks. Run the head out manually by turning the gear - do not force anything. Without a CD inserted, turn the unit on. The tray should close and the head should run to the centre, then back out slightly. Then you should see the lens go up and down 2 1/2 to 3 times.
Tell us what happens please.