I know this is a bit OT, but there is a DIY troubleshooting element!
I have a Kenwood DP-SE7 CD drive that won't read all CDs.
Most CDs play, but when I put some CDs in the drive the player says "no disc".
I cleaned the lens which made no difference.
Today I measured the RF output at 650mV pp, which is better than the 600mV pp specified in the service manual. The RF looks nice and clean on my Tektronix 2246A scope (attached .jpg). So I assume the laser diode is fine.
I tried increasing the laser current so that the RF output was 900 mV pp, but this made no difference. The discs that won't play at the spec level still won't play.
I think the problem is that the drive cannot read the TOC on some discs.
It all looks nice and clean in there, and the grease on the rails and gears is wet i.e. not dried out and sticky.
The discs that won't play are mainly budget labels, but I have played these on other drives with no problems.
There are pots for setting the Focus Error Bias, Tracking Error Balance and Tracking Gain.
Unfortunately the service manual requires the use of a Sony YEDS-18 test disc to adjust these settings. I don't have one of those.
I have little or no experience of repairing or setting up CD players, but maybe there's someone on here that can point me in the right direction.
Even if it's the local "recycling centre".
This looks like a nice piece of kit; I'd like to fix it if I can.
What say guys?
zcx
I have a Kenwood DP-SE7 CD drive that won't read all CDs.
Most CDs play, but when I put some CDs in the drive the player says "no disc".
I cleaned the lens which made no difference.
Today I measured the RF output at 650mV pp, which is better than the 600mV pp specified in the service manual. The RF looks nice and clean on my Tektronix 2246A scope (attached .jpg). So I assume the laser diode is fine.
I tried increasing the laser current so that the RF output was 900 mV pp, but this made no difference. The discs that won't play at the spec level still won't play.
I think the problem is that the drive cannot read the TOC on some discs.
It all looks nice and clean in there, and the grease on the rails and gears is wet i.e. not dried out and sticky.
The discs that won't play are mainly budget labels, but I have played these on other drives with no problems.
There are pots for setting the Focus Error Bias, Tracking Error Balance and Tracking Gain.
Unfortunately the service manual requires the use of a Sony YEDS-18 test disc to adjust these settings. I don't have one of those.
I have little or no experience of repairing or setting up CD players, but maybe there's someone on here that can point me in the right direction.
Even if it's the local "recycling centre".
This looks like a nice piece of kit; I'd like to fix it if I can.
What say guys?
zcx
Attachments
It is more than likely down to a low output from the laser .
Some of the budget labels have lower reflectivity and the laser cannot get a focus. If there is a laser adjustment it may be worth givine it a tweak or even buy a new laser unit.
I had a similar problem years ago - my player was slightly different in that it had very discerning musical tastes - it would only play the 2 Eric Clapton discs I had out of 40 or so !! No amount of tweaking or adjustment changed it.
Andy
Some of the budget labels have lower reflectivity and the laser cannot get a focus. If there is a laser adjustment it may be worth givine it a tweak or even buy a new laser unit.
I had a similar problem years ago - my player was slightly different in that it had very discerning musical tastes - it would only play the 2 Eric Clapton discs I had out of 40 or so !! No amount of tweaking or adjustment changed it.
Andy
Hi,
You don't need the test disc for setting up--in fact it was basically just a disc made to "known" specifications ( the red book standard ) for such things as reflectivity, eccentricity etc. Just use a good representative CD. Follow the manual for setting up but note, focus bias is critical. You can see the effect on the 'scope on the RF. Adjust it so that the "diamond" in the centre is clearest. Tracking gain and focus gain can be surprisingly non critical. If these pots have not been disturbed leave them alone. Tracking error balance is another critical one-- follow the manual to adjust.
If you can get any of the suspect discs to play see if the RF looks any different compared to "good" discs. Not just amplitude-- look at the "sine waves" that make up the signal. Do they appear to "crush" at the top or bottom compared to good discs ?
As Andy says, you can get poor discs ( and discs with CD rot ! ) Always a bit sceptical on that untill I came across a boxed set that had deteriorated. The discs had a real "mottled" look to them when help up to a bright light.
Oh and put the laser power back to where it was. In fact sometimes to much power causes problems. I suspect it may be that a "dimmer" beam is better able to be focused more sharply, as you have to remember solid state lasers (cheapo ones anyway) are nothing like a gas laser for cohereney.
You don't need the test disc for setting up--in fact it was basically just a disc made to "known" specifications ( the red book standard ) for such things as reflectivity, eccentricity etc. Just use a good representative CD. Follow the manual for setting up but note, focus bias is critical. You can see the effect on the 'scope on the RF. Adjust it so that the "diamond" in the centre is clearest. Tracking gain and focus gain can be surprisingly non critical. If these pots have not been disturbed leave them alone. Tracking error balance is another critical one-- follow the manual to adjust.
If you can get any of the suspect discs to play see if the RF looks any different compared to "good" discs. Not just amplitude-- look at the "sine waves" that make up the signal. Do they appear to "crush" at the top or bottom compared to good discs ?
As Andy says, you can get poor discs ( and discs with CD rot ! ) Always a bit sceptical on that untill I came across a boxed set that had deteriorated. The discs had a real "mottled" look to them when help up to a bright light.
Oh and put the laser power back to where it was. In fact sometimes to much power causes problems. I suspect it may be that a "dimmer" beam is better able to be focused more sharply, as you have to remember solid state lasers (cheapo ones anyway) are nothing like a gas laser for cohereney.
That's what I thought.
But in the service manual under adjustment of laser power it says to
"Apply the sensor section of optical power meter on the pickup lens."
Then check that
"On the power from 0.08 to 0.15 mW, when the diffraction grating is correctly aligned with the RF level of 0.6 Vp-p or more."
I take this to mean that the power output of the laser measured on an optical power meter should be between 0.08 and 0.15 mW, and that the RF output should then be 0.6 v pp or more.
I measured 0.65 V pp before I ever touched the laser current pot on the head. So I deduced that the laser output was within spec. Granted I cannot measure the optical power, but cranking up the laser current so the RF output increases about 3dB made no difference to the problem.
I'm beginning to think I might need to clean and regrease the runners that the pickup slides on.
Is it OK to manually slide the pickup away from the centre of the drive so I can get at the inside end of the runners?
Could it could be that the pickup isn't quite getting far enough towards the center of the disc to read the TOC reliably?
But in the service manual under adjustment of laser power it says to
"Apply the sensor section of optical power meter on the pickup lens."
Then check that
"On the power from 0.08 to 0.15 mW, when the diffraction grating is correctly aligned with the RF level of 0.6 Vp-p or more."
I take this to mean that the power output of the laser measured on an optical power meter should be between 0.08 and 0.15 mW, and that the RF output should then be 0.6 v pp or more.
I measured 0.65 V pp before I ever touched the laser current pot on the head. So I deduced that the laser output was within spec. Granted I cannot measure the optical power, but cranking up the laser current so the RF output increases about 3dB made no difference to the problem.
I'm beginning to think I might need to clean and regrease the runners that the pickup slides on.
Is it OK to manually slide the pickup away from the centre of the drive so I can get at the inside end of the runners?
Could it could be that the pickup isn't quite getting far enough towards the center of the disc to read the TOC reliably?
Diffraction grating adjustment. Generally this is an absolute nightmare to do correctly. This should never need touching on the original pickup.
Laser power meters, again good in theory, in fact we HAD to get one for full Sony service accreditation years back. Apart from novelty value it was never used. If the RF meets the spec in the manual thats good enough really. I must admit the RF in your picture looked pretty good, is it that clear and steady in real life ? No jitter or bounce.
As to moving the pickup -- no problem, just don't force any gearing if there is any ( does this one use a "linear motor") and if there are gears just turn them by hand to move the pickup.
Not in correct position at the start ? Dunno !! I have heard of this but can't say I have ever come across it as a fault. Can you see what causes the pickup to come to the rest position. Usually there is a microswitch that signals "the end" of the slide the electronics then giving a litle kick to the sled to position in approximately the correct place.
Sounds a bit silly but see if it will play the duff discs with it stood on either end or upside down -- play about a bit, you have nothing to lose really.
Laser power meters, again good in theory, in fact we HAD to get one for full Sony service accreditation years back. Apart from novelty value it was never used. If the RF meets the spec in the manual thats good enough really. I must admit the RF in your picture looked pretty good, is it that clear and steady in real life ? No jitter or bounce.
As to moving the pickup -- no problem, just don't force any gearing if there is any ( does this one use a "linear motor") and if there are gears just turn them by hand to move the pickup.
Not in correct position at the start ? Dunno !! I have heard of this but can't say I have ever come across it as a fault. Can you see what causes the pickup to come to the rest position. Usually there is a microswitch that signals "the end" of the slide the electronics then giving a litle kick to the sled to position in approximately the correct place.
Sounds a bit silly but see if it will play the duff discs with it stood on either end or upside down -- play about a bit, you have nothing to lose really.
@Mooly
Thanks for your 2 posts.
There are 3 pots (apart from the laser current which I've reset)...
Focus Error Bias; is this same as Focus Bias?
Tracking Error Balance;
Tracking Gain.
I haven't had time to play with these yet.
"If you can get any of the suspect discs to play see if the RF looks any different compared to "good" discs. Not just amplitude-- look at the "sine waves" that make up the signal. Do they appear to "crush" at the top or bottom compared to good discs ?"
Yes. The bad discs seem to crush the TOC at the bottom of the RF waveform; beyond that I can't say, because I get "no disc". Good discs also crush the TOC but to a lesser extent.
"I must admit the RF in your picture looked pretty good, is it that clear and steady in real life ? No jitter or bounce. "
Yes it really is as good as that on a good disc. You can see some bounce on some discs on the outside tracks.
More later when I have time to get the 'scope out.
Cheers.
zcx
Thanks for your 2 posts.
There are 3 pots (apart from the laser current which I've reset)...
Focus Error Bias; is this same as Focus Bias?
Tracking Error Balance;
Tracking Gain.
I haven't had time to play with these yet.
"If you can get any of the suspect discs to play see if the RF looks any different compared to "good" discs. Not just amplitude-- look at the "sine waves" that make up the signal. Do they appear to "crush" at the top or bottom compared to good discs ?"
Yes. The bad discs seem to crush the TOC at the bottom of the RF waveform; beyond that I can't say, because I get "no disc". Good discs also crush the TOC but to a lesser extent.
"I must admit the RF in your picture looked pretty good, is it that clear and steady in real life ? No jitter or bounce. "
Yes it really is as good as that on a good disc. You can see some bounce on some discs on the outside tracks.
More later when I have time to get the 'scope out.
Cheers.
zcx
You may find replacing the pickup "cures" all this. It's one of those problems where there doesn't seem to anything definite wrong, but it's all bit critical as it were.
Mark the Focus Bias pot with a felt tip and see what happens when you tweak it on the scope.
Try the same with the tracking error pot. I know that all sounds very unscientific but theres not much else you can try really.
An odd disc (1 in 100) may give problems for whatever reason but not as many you seem to have.
My own theory is that a lot of pickups fail due to contamination internally, something you cant do much about. I always say, think of a clean glass, put it in the cupboard for 10 years and then look at it.
Mark the Focus Bias pot with a felt tip and see what happens when you tweak it on the scope.
Try the same with the tracking error pot. I know that all sounds very unscientific but theres not much else you can try really.
An odd disc (1 in 100) may give problems for whatever reason but not as many you seem to have.
My own theory is that a lot of pickups fail due to contamination internally, something you cant do much about. I always say, think of a clean glass, put it in the cupboard for 10 years and then look at it.
Sorted
Had a go at the DP-SE7 today and managed to get it to read all the 'bad' disks.
1. Set the laser current to its original setting. Video output nominally 600mV pp per the service manual.
2. Cleaned and regreased (MS4) the slide/rail that the pickup runs on, and the gears that drive the track position. The mechanics certainly moved smoother and quieter but there was no improvement in reading 'bad' disks.
3. Went back to first principles. All the 'good' disks gave an RF signal of > 600mV pp when reading the TOC as the disk was loaded. All the 'bad' disks gave < 600mV pp; some as low as 400mV.
4. Did that mean that the reflectivity of the 'bad' disks was lower, and that's why the player couldn't read the TOC? Cranked up the laser current in an attempt to compensate, but instead the RF waveform became even more distorted when reading the TOC. Reset the laser current.
5. Tried setting the Tracking Error Balance per the service manual. This made no difference to the drives ability to read the 'bad' disks at all. In fact moving the pot over > 90 degrees made no difference when playing good disks. At one extreme the drive lost lock and wound the disc speed up to about 3000 rpm! At the other extreme the drive ran backwards!
6. Finally tried setting the Focus Error Bias. This produced an immediate improvement. After a few tries found a setting that would allow all disks to play reliably.
The 'best' setting of the Focus Error Bias was about 45 degrees ACW from the original setting. I'd swear this player had never been tampered with in its life before, so why such a big adjustment?
Maybe it had never been set up properly in the first place. Or maybe something had changed in the player that required compensation. Who knows?
Anyway many thanks poynton and mooly for your help.
zcx
Had a go at the DP-SE7 today and managed to get it to read all the 'bad' disks.
1. Set the laser current to its original setting. Video output nominally 600mV pp per the service manual.
2. Cleaned and regreased (MS4) the slide/rail that the pickup runs on, and the gears that drive the track position. The mechanics certainly moved smoother and quieter but there was no improvement in reading 'bad' disks.
3. Went back to first principles. All the 'good' disks gave an RF signal of > 600mV pp when reading the TOC as the disk was loaded. All the 'bad' disks gave < 600mV pp; some as low as 400mV.
4. Did that mean that the reflectivity of the 'bad' disks was lower, and that's why the player couldn't read the TOC? Cranked up the laser current in an attempt to compensate, but instead the RF waveform became even more distorted when reading the TOC. Reset the laser current.
5. Tried setting the Tracking Error Balance per the service manual. This made no difference to the drives ability to read the 'bad' disks at all. In fact moving the pot over > 90 degrees made no difference when playing good disks. At one extreme the drive lost lock and wound the disc speed up to about 3000 rpm! At the other extreme the drive ran backwards!
6. Finally tried setting the Focus Error Bias. This produced an immediate improvement. After a few tries found a setting that would allow all disks to play reliably.
The 'best' setting of the Focus Error Bias was about 45 degrees ACW from the original setting. I'd swear this player had never been tampered with in its life before, so why such a big adjustment?
Maybe it had never been set up properly in the first place. Or maybe something had changed in the player that required compensation. Who knows?
Anyway many thanks poynton and mooly for your help.
zcx
Good you have sorted it 🙂 Reading your last post 600 mv to 400 mv on the bad discs is a huge variation. There is only the reflectivity of the disc involved for that. Very strange. Are they very "budget" end discs. Do they look less shiney in the light at all.
At least the player seems OK -- and better for it's service 😉
At least the player seems OK -- and better for it's service 😉
@Mooly
The variation is only about 3.5dB, so not all that really. It seems that as long as the player can read the TOC it's happy to read the tracks.
I can't tell if the 'bad' CDs look less shiny; perhaps a bit yellow with age in a few cases! But yes they are mostly budget discs, although there's a pukka Polydor release amongst them.
If it was purely a reflectivity problem I don't understand is why turning up the laser current didn't make it better. I guess if the laser is out of focus then more power can make things worse.
Also I don't understand what you're looking at when you monitor the RF; it's looks like an output from the DSP chip on this player.
I forgot to mention that I tried playing CDs in various orientations but the player has a tilt switch and goes to standby if you try and play it on its side/back/upside down.
Thanks again for your help.
zcx
The variation is only about 3.5dB, so not all that really. It seems that as long as the player can read the TOC it's happy to read the tracks.
I can't tell if the 'bad' CDs look less shiny; perhaps a bit yellow with age in a few cases! But yes they are mostly budget discs, although there's a pukka Polydor release amongst them.
If it was purely a reflectivity problem I don't understand is why turning up the laser current didn't make it better. I guess if the laser is out of focus then more power can make things worse.
Also I don't understand what you're looking at when you monitor the RF; it's looks like an output from the DSP chip on this player.
I forgot to mention that I tried playing CDs in various orientations but the player has a tilt switch and goes to standby if you try and play it on its side/back/upside down.
Thanks again for your help.
zcx
Hi,
In the early days of CD I attended a 3 day Sony course at Sony UK in Thatcham. We absolutely pulled all the theory apart.
You might have seen this,
http://www.repairfaq.org/REPAIR/F_cdfaqd.html#CDFAQD_004
which sort of explains quite a bit of what goes on. It's not too heavy going.
It always surprises folks that the RF always looks the same on a 'scope no matter what the disc.
In the early days of CD I attended a 3 day Sony course at Sony UK in Thatcham. We absolutely pulled all the theory apart.
You might have seen this,
http://www.repairfaq.org/REPAIR/F_cdfaqd.html#CDFAQD_004
which sort of explains quite a bit of what goes on. It's not too heavy going.
It always surprises folks that the RF always looks the same on a 'scope no matter what the disc.
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