Hi Community,
I’ve recently acquired this amazing player in an almost perfect shape where the vast majority of my CD collection is read perfectly and track skip usually happening in a couple of secs.
That said there is an handful of disks that, despite their TOC is read in a glance, the first track takes forever to start.
Lens has been cleaned, linear guides have been greased but those few CDs really hurts.
I’m keen to think of the focus bias non being perfectly set but given the lack of a service manual I can’t even look for the RF pin
Any suggestions? On the pick-up I see the typical APC the TB and the FB triggers.
Thanks for any hint you’re willing to share
I’ve recently acquired this amazing player in an almost perfect shape where the vast majority of my CD collection is read perfectly and track skip usually happening in a couple of secs.
That said there is an handful of disks that, despite their TOC is read in a glance, the first track takes forever to start.
Lens has been cleaned, linear guides have been greased but those few CDs really hurts.
I’m keen to think of the focus bias non being perfectly set but given the lack of a service manual I can’t even look for the RF pin
Any suggestions? On the pick-up I see the typical APC the TB and the FB triggers.
Thanks for any hint you’re willing to share
Forgot to say that
Again thanks for sharing your experience.
- CD-R of very different quality are read faultless
- I own an album in two copies: the first CD, the older and scratched, is read perfectly, the second, newer and pristine, doesn’t start at all showing the defect mentioned in the first post.
Again thanks for sharing your experience.
Hi all, I was able to spend a little time looking at the servo, taking pictures and making some measurements. This might eventually help others as well.
Board (Top, Audio / Bottom, Servo)
Servo board detailed
Pickup (KSS-281A) close-ups
RF - test disc
TE
FE
The RF pattern proves the laser is in very good shape which was also confirmed, as shared in the first post, by the TOC reading time (below 2 secs) and track jumping taking less than 2 secs with the vast majority of discs.
The TE and FE patterns are however pretty similar when compared between the track playing and track not playing and give me no real hint.
The Servo board has no potentiometers and the only "tweakable" ones are the three sitting on the pickup. Rotating them is however tricky because they seems "stuck" in their current position and the screwdriver in my possess are not the best fitting one.
Any hint? Could it be worthy to replace the electro caps on servo? especially those near IC23, IC24 and IC25?
Thanks again for your time.
Board (Top, Audio / Bottom, Servo)
Servo board detailed
Pickup (KSS-281A) close-ups
RF - test disc
TE
| Track playing correctly | Disc spinning but track not playing |
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FE
| Track playing correctly | Disk spinning but track not playing |
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The RF pattern proves the laser is in very good shape which was also confirmed, as shared in the first post, by the TOC reading time (below 2 secs) and track jumping taking less than 2 secs with the vast majority of discs.
The TE and FE patterns are however pretty similar when compared between the track playing and track not playing and give me no real hint.
The Servo board has no potentiometers and the only "tweakable" ones are the three sitting on the pickup. Rotating them is however tricky because they seems "stuck" in their current position and the screwdriver in my possess are not the best fitting one.
Any hint? Could it be worthy to replace the electro caps on servo? especially those near IC23, IC24 and IC25?
Thanks again for your time.
Sorry, but RF signal is not clean, it is noisy top and down sides. I've seen cd laser faults, and even today I don't have clear when a laser diode is working well or not. A laser diode faulty can be caused by a lot of causes. A laser diode can provide laser power, but can be cause a lot of phase noise. A laser diode must have a good spectral and phase. Sorry for the speech...
Maybe your laser diode can be solved adjusting its potentiometers. I've seen that these tiny potentiometers are not stable in its values, it have some value drift in time, so, maybe it only needs a adjust.
Its value are 2k2.
These potentiometes are very hard, tough to move. I'd replace it for another ones more easy to adjust.
I've seen in some Sony Kss lasers that the lens must be re adjusted in its position, it occurs because plastic pieces deformed thorought time. It is not easy to adjust it.
And finishing, for to be sure about laser power, a laser power meter is imperious. Indirect measures are not trustworthly.
TE and FE patterns sometimes are not helpful, even sometimes are misleading. I do the final adjusts with CD discs in bad state, bent, scratched, etc...
And please, don't replace any capacitor. Don't fall in this stupid vogue of replacing capacitors without any real cause.
Maybe your laser diode can be solved adjusting its potentiometers. I've seen that these tiny potentiometers are not stable in its values, it have some value drift in time, so, maybe it only needs a adjust.
Its value are 2k2.
These potentiometes are very hard, tough to move. I'd replace it for another ones more easy to adjust.
I've seen in some Sony Kss lasers that the lens must be re adjusted in its position, it occurs because plastic pieces deformed thorought time. It is not easy to adjust it.
And finishing, for to be sure about laser power, a laser power meter is imperious. Indirect measures are not trustworthly.
TE and FE patterns sometimes are not helpful, even sometimes are misleading. I do the final adjusts with CD discs in bad state, bent, scratched, etc...
And please, don't replace any capacitor. Don't fall in this stupid vogue of replacing capacitors without any real cause.
Addendum:
First of all, I'd try to adjust, but with other kind of potentiometers. This potentiometers can be suitable for it:
https://es.aliexpress.com/item/1005005310181385.html
It should be important to take note of APC potentiometer value, for to remain laser power value. I see in the pictures that to take an adjust procedure is viable with care, even with the cd player in horizontal. It is not easy, but not impossible.
First of all, I'd try to adjust, but with other kind of potentiometers. This potentiometers can be suitable for it:
https://es.aliexpress.com/item/1005005310181385.html
It should be important to take note of APC potentiometer value, for to remain laser power value. I see in the pictures that to take an adjust procedure is viable with care, even with the cd player in horizontal. It is not easy, but not impossible.
Many thanks @ManoloMos for your recommendations!
I've made some progresses today by applying with a brush a deoxidising liquid on those three trimmers and by changing the FB I've been able to get those few CD not starting to be played. However the performances in terms of track jump and track start are not as good as with the other CDs. So the problem has been vastly mitigated but there is still room for improvement.
I've also took some other pic from an analog oscilloscope to better show the RF pattern quality.
I'll order the SMD trimmer and see if replacing them anything improves. Last chance, will be to measure ESR of the caps near the IC and eventually consider their replacement if out of spec.
In the end I agree that the RF pattern is not the cleanest I've seen but for a 33 yrs old machine with the factory pickup, I think it's of the best I've seen so far.
Cheers, Riccardo
You're always more than welcome when you give speech on lasers
I've made some progresses today by applying with a brush a deoxidising liquid on those three trimmers and by changing the FB I've been able to get those few CD not starting to be played. However the performances in terms of track jump and track start are not as good as with the other CDs. So the problem has been vastly mitigated but there is still room for improvement.
I've also took some other pic from an analog oscilloscope to better show the RF pattern quality.
| RF (0.5V, ref CD, pre) | RF (1V, ref CD, pre) |
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| RF (0.5V, ref CD, post) | RF (0.5V, ref CD1, post) | RF (0.5V, ref CD2, post) | RF (0.5V, ref CD3, post) |
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I'll order the SMD trimmer and see if replacing them anything improves. Last chance, will be to measure ESR of the caps near the IC and eventually consider their replacement if out of spec.
In the end I agree that the RF pattern is not the cleanest I've seen but for a 33 yrs old machine with the factory pickup, I think it's of the best I've seen so far.
Cheers, Riccardo
Another thing, don't forget to use an oscilloscope probe attenuator by 10, if you use a x1 probe, high impedance RF out can be deformed. Forget to culprit capacitors, it is not their fault, RF signal you take from the test point are take from the laser pickup output directly, so, don't waste time in capacitors.
Thanks @ManoloMos ,I agree with you on the fact that RF is directly spit out of the pickup but I think capacitors here play a role with regard to Tracking gain and Focus Gain. Differently from how the KSS-281A is implemented on CDP-X777ES (the only other play I know that uses this pickup) where Trading Gain and Focus Gain trimmer are available on the Servo board, here this trimmers are not available making me thinking of a sort of retro-feedback implementation where the electronic is responsible for levelling these signals.
Unfortunately I don't have schematics here (DP-70V are impossible to get as much as for many other Accuphase ) so I can't confirm my ideas. However if this is the case maybe the caps can have a role on how this retro-feedback mechanism react.
What's your impression on this?
Unfortunately I don't have schematics here (DP-70V are impossible to get as much as for many other Accuphase ) so I can't confirm my ideas. However if this is the case maybe the caps can have a role on how this retro-feedback mechanism react.
What's your impression on this?
Looking at the board description from the DP-70V flyer
and checking the DALLAS DS1267-010 datasheet it's realistic to assume that the Tracking and Focus Gain functions are found in this IC (16) and that this is controlled somehow by servo signal processing (15). This confirms my idea of TG and FG being automatically set by to the optimal value depending on the signal coming from the pickup.
and checking the DALLAS DS1267-010 datasheet it's realistic to assume that the Tracking and Focus Gain functions are found in this IC (16) and that this is controlled somehow by servo signal processing (15). This confirms my idea of TG and FG being automatically set by to the optimal value depending on the signal coming from the pickup.
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KSS-271a and KSS-272a are almost equals, however, Sony CDP-X33ES with KSS-271A has tracking and gain focus adjustment, but Sony CDP-X339es with KSS-272a does not have tracking and gain focus adjustment. I don't think that tracking and gain focus in in CDP-X33es with KSS-272a is electronic, I think the explanation is more simple, tracking and gain focus is setted to a fixed value, with a simple resistor or something like that.
Don't waste time in this issues that does not help in your case.
Another thing, I don't find the DALLAS DS1267-010 IC that you quote in the digital procesor picture you published.
There is another issue, when I look information about your Accuphase DP-70V. If seems that DP-70 without V has a Sony BU-1C laser pickup, however your DP-70V has the KSS-281a. But, however, your mechanism is similar that used BU-1C and KSS-190A mechanisms.
But, let's go to the problem and the most viable solution. As you can see, there is no other adjustmensts that the tiny potentiometers. These tiny potentiometers has a drift over time. If you can adjust it, I think that should be enogh. The problem is that these potentiometers are tough, I'd recomend replace. But you can try adjusting Focus and Tracking Bias. Try to do the adjust in a CD in the midle and paused, horizonal position if it is possible(It is not easy, I know).
Don't waste time in this issues that does not help in your case.
Another thing, I don't find the DALLAS DS1267-010 IC that you quote in the digital procesor picture you published.
There is another issue, when I look information about your Accuphase DP-70V. If seems that DP-70 without V has a Sony BU-1C laser pickup, however your DP-70V has the KSS-281a. But, however, your mechanism is similar that used BU-1C and KSS-190A mechanisms.
But, let's go to the problem and the most viable solution. As you can see, there is no other adjustmensts that the tiny potentiometers. These tiny potentiometers has a drift over time. If you can adjust it, I think that should be enogh. The problem is that these potentiometers are tough, I'd recomend replace. But you can try adjusting Focus and Tracking Bias. Try to do the adjust in a CD in the midle and paused, horizonal position if it is possible(It is not easy, I know).
Interesting thread and a nice player
Could I just offer a few thoughts...
1/ When viewing the RF make sure you use the correct ground point. Chassis ground often doesn't cut it in terms of noise, you need the correct ground used by the RF amp. That could be IC27 on your pictures (an SMD chip under the board) and there is an 'A Ground' point next to your RF test point. Make sure you don't create a ground loop with the scope (measure for any voltage difference first before connecting) as some players use a virtual ground for the RF amp that could be floating at 2.5 volts dc. Unlikely but check.
2/ Typical RF amplitude for most players is 1.2 to 1.5v pk pk as a generalisation. Make sure your probe is correctly compensated as any error here will greatly alter the amplitude you see on screen if using a divider probe.
3/ FB has to be adjusted for max amplitude of the RF and the clearest 'diamond' in the RF pattern.
4/ TB (or E/F balance) should be checked (again a generalisation and not model specific) by looking with the scope at the tracking error waveform. Slow the timebase down and then jump tracks from an early track to one nearer the disc end. The waveform will change but should appear as notionally symmetrical above and below a 'zero line' through the middle. If it seems to be asymmetric and shifted above or below this imaginary line as the player is performing the track jumps then the balance should be adjusted. Try both AC and DC coupling on the scope to get a feel for how it looks.
Do not use any CDR or RW for any adjustments no matter how good they may appear to be.
Good luck
Could I just offer a few thoughts...
1/ When viewing the RF make sure you use the correct ground point. Chassis ground often doesn't cut it in terms of noise, you need the correct ground used by the RF amp. That could be IC27 on your pictures (an SMD chip under the board) and there is an 'A Ground' point next to your RF test point. Make sure you don't create a ground loop with the scope (measure for any voltage difference first before connecting) as some players use a virtual ground for the RF amp that could be floating at 2.5 volts dc. Unlikely but check.
2/ Typical RF amplitude for most players is 1.2 to 1.5v pk pk as a generalisation. Make sure your probe is correctly compensated as any error here will greatly alter the amplitude you see on screen if using a divider probe.
3/ FB has to be adjusted for max amplitude of the RF and the clearest 'diamond' in the RF pattern.
4/ TB (or E/F balance) should be checked (again a generalisation and not model specific) by looking with the scope at the tracking error waveform. Slow the timebase down and then jump tracks from an early track to one nearer the disc end. The waveform will change but should appear as notionally symmetrical above and below a 'zero line' through the middle. If it seems to be asymmetric and shifted above or below this imaginary line as the player is performing the track jumps then the balance should be adjusted. Try both AC and DC coupling on the scope to get a feel for how it looks.
Do not use any CDR or RW for any adjustments no matter how good they may appear to be.
Good luck
It's the IC numbered 16 in the picture
The DP-70V was released in two versions: one with KSS-190A and one (newer) with KSS-281A with RF amp embedded on the pickup. The DP-70 is an older model using BU-1C
As written in post #6 I've been able to unblock the trimmer placed on the pickup PCB and to slightly adjust the FB to ensure the CDs that were creating issues were "somehow" read.
That's tough... I need to work as a car mechanic under a bridge crane
You are right, I'll repeat the measurements with a extending cable to connect to the servo pins with a better and more reliable solution rather then floating probes. This should go hand in hand with Manolomos recommendation to use probe set at 10x
In the analog scope, the RF has an amplitude larger then the digital scope (this is correct with a measured Vp-p of 1.22v).
That's the plan but hard to achieve with a 26kg monster, a tiny FB trimmer poorly positioned (engineers where are you?) on the pickup while avoid to move the pickup. At least for me this is tricky and I'm missing those players were trimmers are all on the PCB and not on the pickup.
Roger! I'll do
Never used, only pristine CDs (12 or 8cm) are used for calibration.
Thanks both of you for the useful comments!
Hi all,
I've been able to complete during this holidays the DP-70V servo board recap and to better tune TB and FB.
Despite the recap has lead to better numbers with regard to ESR and VLoss, and the TB and FB recalibration now grants the TOC to be read in less than 2secs for all CDs of my collection, I still face troubles on reading the first track of <1% them (actually 1 CDs out of more than 200).
For posterity I confirm that whilst the APC trigger change is immediately reflected in Vp-p value change (goes up to 1.8V), the FB and TB changes have very little impact on the FE and TE traces. I also confirm that since the player doesn't like at all to play CDs upside-down, making live changes to FB and TB while playing a disk and watching the scope has been impossible and I was only able to tweak these triggers my "assessing" the final on the 1st track reading capability.
After tweaking the "offending" CD's TOC is read instantly but the RF trace is more blurry than other making me thinking that either the substrate is "somehow" disliked by this player or, as described by @ManoloMos , the pickup is within a certain degree "compromised" (although the neglectable percentage on which the issue occurs over the collection makes me favour the first idea of disliked substrate).
Finally It's worthy reporting that this behaviour is random and only affect the first track: playing the 1st track could take from 2 secs (best case) to 30secs (worst case) as if the track start is not "found"; more "external" tracks are instead reach consistently under 3 secs.
Being not able to improve any further the reading of the first track, I consider this case "closed" given this old gentleman the right to dislike a CD or two after more than 30years.
Cheers, Riccardo
I've been able to complete during this holidays the DP-70V servo board recap and to better tune TB and FB.
Despite the recap has lead to better numbers with regard to ESR and VLoss, and the TB and FB recalibration now grants the TOC to be read in less than 2secs for all CDs of my collection, I still face troubles on reading the first track of <1% them (actually 1 CDs out of more than 200).
| RF (0.5V, 10x calibrated probe, ref CD, post recap) |
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For posterity I confirm that whilst the APC trigger change is immediately reflected in Vp-p value change (goes up to 1.8V), the FB and TB changes have very little impact on the FE and TE traces. I also confirm that since the player doesn't like at all to play CDs upside-down, making live changes to FB and TB while playing a disk and watching the scope has been impossible and I was only able to tweak these triggers my "assessing" the final on the 1st track reading capability.
After tweaking the "offending" CD's TOC is read instantly but the RF trace is more blurry than other making me thinking that either the substrate is "somehow" disliked by this player or, as described by @ManoloMos , the pickup is within a certain degree "compromised" (although the neglectable percentage on which the issue occurs over the collection makes me favour the first idea of disliked substrate).
Finally It's worthy reporting that this behaviour is random and only affect the first track: playing the 1st track could take from 2 secs (best case) to 30secs (worst case) as if the track start is not "found"; more "external" tracks are instead reach consistently under 3 secs.
Being not able to improve any further the reading of the first track, I consider this case "closed" given this old gentleman the right to dislike a CD or two after more than 30years.
Cheers, Riccardo
It is very difficult to say what is causing the problems here. Generally a 'healthy' player will tolerate a wide range of misalignment and still play and operate 'normally'. Players that are super critical on alignment usually have an underlying issue.
If the player has a PLL adjustment it would be worth checking that. This is an adjustment that sets the free run frequency of an oscillator and is typically 4.3218Mhz on many players. When locked and playing a disc the frequency should locked. When not playing the frequency is set to as close to this point as possible for a fast and accurate lock.
Not sure if you have seen this which covers some alignment procedures:
https://www.diyaudio.com/community/threads/sony-cdp790-and-kss240-restoration-project.226288/
If the player has a PLL adjustment it would be worth checking that. This is an adjustment that sets the free run frequency of an oscillator and is typically 4.3218Mhz on many players. When locked and playing a disc the frequency should locked. When not playing the frequency is set to as close to this point as possible for a fast and accurate lock.
Not sure if you have seen this which covers some alignment procedures:
https://www.diyaudio.com/community/threads/sony-cdp790-and-kss240-restoration-project.226288/
Thanks @Mooly for the hint but while the servo has a PLCK test point to likely check the current frequency I've no trimmers for tweaking this value and I also wonder if there's any specific "adjustment" steps to be done (e.g. put this pin to ground and switch the player on...etc) for make the tweaks.
The only triggers I have are those located on the pickup (TB, FB, APC), but given the very uncomfortable position, the magnetic rails opposing a very limited resistance when rotating the trimmers, the heavy weight (~30Kg) and the fact that the player doesn't love to play discs upside-down finding the right values it's ridiculously though.
The only triggers I have are those located on the pickup (TB, FB, APC), but given the very uncomfortable position, the magnetic rails opposing a very limited resistance when rotating the trimmers, the heavy weight (~30Kg) and the fact that the player doesn't love to play discs upside-down finding the right values it's ridiculously though.
The PLL adjustment is sometimes an adjustable coil rather than a trimmer which of course is where a service manual comes in.
Any adjustments should always be done in the normal position, if you have it upside down or at an angle then the servo is artificially correcting for that position by increasing or decreasing as needed the focus and tracking coil voltages.
I've no easy answers I'm afraid
Any adjustments should always be done in the normal position, if you have it upside down or at an angle then the servo is artificially correcting for that position by increasing or decreasing as needed the focus and tracking coil voltages.
I've no easy answers I'm afraid
Since you can't get enough until you get enough, I spent more hours tweaking FB (because I learned that that was a multi-turn trimmer)
in the end I've obtained the result desired! Now all CDs are correctly read with the TOC of the "worst" CD acquired in 3.5s (ref CD is 1.5s) and the first track "usually" starting after 5s (ref CD is 1s).
Thanks to anyone who has contributed to the discussion, hope this could be helpful for others in the future.
in the end I've obtained the result desired! Now all CDs are correctly read with the TOC of the "worst" CD acquired in 3.5s (ref CD is 1.5s) and the first track "usually" starting after 5s (ref CD is 1s).
| Best (ref CD, 1s to first track, Vp-p 1.4V) | Average (99% of collection, 2.5s to first track, Vp-p 1.2V) | Worst (1% of collection, 5s to first track, Vp-p 1.36V) |
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Thanks to anyone who has contributed to the discussion, hope this could be helpful for others in the future.