Hi and thanks,
I did not touch any other pots.
I don't quit understand: is it adviable to buy 10 of these cheap heads or should I purchase an original Sony (like I did last week..)
I asked my brother about his scope and it appears to be in working condition. It's a 20 MHz dual beam; wil that do for this job? It will take some time before I can get it.
In the meantime I want to read about setting up lasers. I cannot find a service DCD1420 manual via Google. Do you happen to know where I can get one or where I can find documents on setting up lasers (I can read English, German, French and... Dutch)? I read about 'eye patterns' but I don't remember (or never knew) what that means.
I really appreciate your help!
Greetings,
Willem
I did not touch any other pots.
I don't quit understand: is it adviable to buy 10 of these cheap heads or should I purchase an original Sony (like I did last week..)
I asked my brother about his scope and it appears to be in working condition. It's a 20 MHz dual beam; wil that do for this job? It will take some time before I can get it.
In the meantime I want to read about setting up lasers. I cannot find a service DCD1420 manual via Google. Do you happen to know where I can get one or where I can find documents on setting up lasers (I can read English, German, French and... Dutch)? I read about 'eye patterns' but I don't remember (or never knew) what that means.
I really appreciate your help!
Greetings,
Willem
Hi Willem,
I lost all my service manuals when I sold my shop. Boy to I ever miss those manuals!!! Eight 4 drawer filing cabinets full!
I would buy the one orig part, given the choice. It never pays to play with a deal that doesn't sound right.
Is it possible the wires to the head are catching on something? Play a CD until it stops and check to see if the wires get tight. Even one wire of the bunch. Some machines had a problem with this, can't remember the makes.
Make absolutely positive that your probe remains on the X10 setting!!
From a couple posts back ...
-Chris
I lost all my service manuals when I sold my shop. Boy to I ever miss those manuals!!! Eight 4 drawer filing cabinets full!
Right now, connect the oscilloscope and get some answers first. make sure the power supply lines are clear of high frequency noise or oscillations, and the laser current test point should also be free from any noise.
I would buy the one orig part, given the choice. It never pays to play with a deal that doesn't sound right.
Good deal! They should not be so far out that another head does not work, but will need correction for a new head to play perfectly. As I see it, you have two faults. The oscillation on the focus servo (check the filter) and something that causes a skip about 1/2 the way through.
Is it possible the wires to the head are catching on something? Play a CD until it stops and check to see if the wires get tight. Even one wire of the bunch. Some machines had a problem with this, can't remember the makes.
Buy one from Denon, a paper copy. They are not expensive, probably around $20, maybe less.
The proper Denon service manual will explain this. You connect your scope to the "RF" test point. There are two rows of test pins, the terminal is labeled there.
Make absolutely positive that your probe remains on the X10 setting!!
Does it have a 0.5 uS/Div setting? Put the unit aside for now until you get your information together with the 'scope.
From a couple posts back ...
You can use 1 uS/Div, but this is much more difficult to do. It can be done still.
-Chris
We used to change KSS210's on Aiwa music centres amongst many others. And the wires caught on those too !!
The main problem on those and many others was that the player ( a 3 disc auto changer ) was the top unit so got all the heat and dust convected up to it. All in one cabinet you see.
Someone must have an old manualof a player that uses the 210, the principle is the same.
Dare I say, if you try another head and run into problems, get the 'scope, no let's get the 'scope anyway, and let's see if we can work through it.
You would need to identify as test points, TE, FE. RF.
A 210 should work straight off without all this agro. If it doesn't something else is going on.
The main problem on those and many others was that the player ( a 3 disc auto changer ) was the top unit so got all the heat and dust convected up to it. All in one cabinet you see.
Someone must have an old manualof a player that uses the 210, the principle is the same.
Dare I say, if you try another head and run into problems, get the 'scope, no let's get the 'scope anyway, and let's see if we can work through it.
You would need to identify as test points, TE, FE. RF.
A 210 should work straight off without all this agro. If it doesn't something else is going on.
Hi Chris and Mooly,
I shall check the carriage wires and maybe connect them anew just to make shure they don't put tension on the slegde.
I found and downloaded the service manual (at servicemanuals.com for $ 15). I'll dive into that while awaiting the scope and a new head.
Thanks again; it is great to find so much knowledgeable help.
I will report back to you.
Best regards,
Willem
I shall check the carriage wires and maybe connect them anew just to make shure they don't put tension on the slegde.
I found and downloaded the service manual (at servicemanuals.com for $ 15). I'll dive into that while awaiting the scope and a new head.
Thanks again; it is great to find so much knowledgeable help.
I will report back to you.
Best regards,
Willem
That's good. One other thing. I personally would not use ISO for lens cleaning. In the 1980's Sony recommended it, then did a U turn when coated optics were introduced. If the lens has a blueish tinge it's coated - - most are.
I have the proper cleaning fluid from Sony but I suspect camera lens cleaner would be OK, but I have not tried it. Never use glass cleaner as that has ammonia in it. Warm water with the tiniest drop of detergent should be fine to. Look at the lens with a torch to make sure there are no water marks left.
I have the proper cleaning fluid from Sony but I suspect camera lens cleaner would be OK, but I have not tried it. Never use glass cleaner as that has ammonia in it. Warm water with the tiniest drop of detergent should be fine to. Look at the lens with a torch to make sure there are no water marks left.
So, I have been reading the service manual over and over again and I think I'm beginning to grasp some understanding of the setup procedure. One thing bothers me, though: I seem to be needing the reference disk CA-1094. I understand that to be a pretty expensive and not copy-able item. Is there a way to setup the laser without this disk?
I'm still awaiting the new head and the 'scope (may take a while). I'll try the old head tonight.
Willem
I'm still awaiting the new head and the 'scope (may take a while). I'll try the old head tonight.
Willem
Fortunately that's one thing that isn't a problem. You just need a good commercial disc, not a CDR. When you look at the RF or eye pettern you will see that it looks identical for every disc you put in.
When you scope it try a few discs as the reflectivity does vary and try and pick an "average" one. A typical RF value will be around 1.2 to 1.5 volts peak to peak. You just might pick a disc that gives more, say 1.7 or 1.8 or very much less, say 0.9 volts.
Go for an average. The test disc is just a disc to known standards, reflectivity, eccentricity, thickness etc. It's the one that definitely isn't needed
You really do need the scope though. If the manual get's a bit heavy with the set up procedure ( like making RC networks up and generally getting involved ) there are easy ways and means
When you scope it try a few discs as the reflectivity does vary and try and pick an "average" one. A typical RF value will be around 1.2 to 1.5 volts peak to peak. You just might pick a disc that gives more, say 1.7 or 1.8 or very much less, say 0.9 volts.
Go for an average. The test disc is just a disc to known standards, reflectivity, eccentricity, thickness etc. It's the one that definitely isn't needed
You really do need the scope though. If the manual get's a bit heavy with the set up procedure ( like making RC networks up and generally getting involved ) there are easy ways and means
Hi Willem, Mooley,
Yes, CA1094 is simply a commercial CD that's characteristics were known. It is important for following the factory ethos to set focus and tracking gain. Over the years, Denon used other CD's as the original became unavailable and the test oscillator frequencies were changed to compensate.
Now the good news. Using the servo noise as both Mooley and I do, there is no need to make a filter or use the test CD. Place the gain controls where they originally were. You should be able to feel a small "dent" in the carbon track where the contact pressed down for years. Turn slowly and use you finger tips lightly so you can feel the small "dent". The gain is not that critical for home machines and the original pickup worked. Normally the gains do not need to be adjusted when changing a head unless you are doing a "perfect job". Without practice, don't worry about that yet. Once you have the rest of the machine set up, you can come back to this and optimize these adjustments.
The highly reflective discs giving a strong RF, or eye pattern, is useful in getting the machine to lock up easier for initial adjustments. Go for an average one after that as Mooly suggested. One thing to look for is a clean eye pattern, without a lot of noise, and one where the horizontal wavering is minimized. That means low jitter.
-Chris
Yes, CA1094 is simply a commercial CD that's characteristics were known. It is important for following the factory ethos to set focus and tracking gain. Over the years, Denon used other CD's as the original became unavailable and the test oscillator frequencies were changed to compensate.
Now the good news. Using the servo noise as both Mooley and I do, there is no need to make a filter or use the test CD. Place the gain controls where they originally were. You should be able to feel a small "dent" in the carbon track where the contact pressed down for years. Turn slowly and use you finger tips lightly so you can feel the small "dent". The gain is not that critical for home machines and the original pickup worked. Normally the gains do not need to be adjusted when changing a head unless you are doing a "perfect job". Without practice, don't worry about that yet. Once you have the rest of the machine set up, you can come back to this and optimize these adjustments.
The highly reflective discs giving a strong RF, or eye pattern, is useful in getting the machine to lock up easier for initial adjustments. Go for an average one after that as Mooly suggested. One thing to look for is a clean eye pattern, without a lot of noise, and one where the horizontal wavering is minimized. That means low jitter.
No setup discs are "copyable". There are too many parameters and precise "defects" in the reflective surface or top surface. Test tapes are not copyable either - just for reference.
-Chris
Hi,
I replaced the old laser unit, which brought me back to where I started (fortunately; as Mooly predicted: nothing lost yet). The player now repeats and skips parts of the difficult discs. This partly appears to be function of the OF-offset pot, but I cannot eliminate the problems with it.
Thanks again for your kind attention (and patience).
Willem
I replaced the old laser unit, which brought me back to where I started (fortunately; as Mooly predicted: nothing lost yet). The player now repeats and skips parts of the difficult discs. This partly appears to be function of the OF-offset pot, but I cannot eliminate the problems with it.
Thanks again for your kind attention (and patience).
Willem
Hi Willem,
You really need to be able to look a the RF pattern, or eye pattern.
One thought though, check the voltage across the sled motor as your CD plays. I normally use a 'scope for this, but a fast reading DVM, or better yet, an analog meter would do this.
What you are looking for is an abnormal rise in voltage across the motor, followed by a reversal in polarity. This could indicate some hangup in the motion. More importantly, your motor could have a dead spot.
The sled motor servo is simply a filtered average of what the tracking servo is doing. As the lens swings towards one end of travel, the average DC level goes up. The average is applied to the sled motor so it can nudge the head along, which will reduce the DC on both the tracking and sled servos. It is normal to see the tracking servo reverse polarity a bit.
-Chris
You really need to be able to look a the RF pattern, or eye pattern.
One thought though, check the voltage across the sled motor as your CD plays. I normally use a 'scope for this, but a fast reading DVM, or better yet, an analog meter would do this.
What you are looking for is an abnormal rise in voltage across the motor, followed by a reversal in polarity. This could indicate some hangup in the motion. More importantly, your motor could have a dead spot.
The sled motor servo is simply a filtered average of what the tracking servo is doing. As the lens swings towards one end of travel, the average DC level goes up. The average is applied to the sled motor so it can nudge the head along, which will reduce the DC on both the tracking and sled servos. It is normal to see the tracking servo reverse polarity a bit.
-Chris
A few days ago I adjusted the KSS-150A of my old Nakamichi CD-4 (same procedure as for the KSS-210A). I had never done that before,
but afterwards I found it to be very do-able.
I have the benefit of having a colleague who used to work as a service technician. He must have replaced and adjusted many laser units in his life. His advice was to ignore the official procedure described by Sony. In his experience it didn't work, use the eye-pattern instead (like many have already said).
This is what the eye pattern should look like:
As you can see the 15 year old laser still does slightly better than 1 Vpp.
Play a CD and find the RF-pin. In my CD-4 there was a long row of testpins without any descriptions printed on the PCB. I just touched one pin at a time with the probe until I found the one with the eye-pattern.
The correct setting of the scope is 0.5 uS/div and 0.5 V/Div (1x probe was no problem on my player, if you use a 10x probe use the 50 mV/div setting to compensate for the 10x attenuation). The coupling should be set to AC.
The aim is to make the eye-pattern as wide as possible on the Y-axis of the scope. Start by adjusting the bal. pots (on the CD-4 they are labeled EF-bal and F-bias). When you got the eye pattern as wide as possible, chances are you can leave the gain pots alone, they are less critical. I did adjust them the way my colleague said: turn until the signal starts to drop away and then slightly back.
An added bonus was that I bought a focus-CD many years ago (never used it until now, though). On it are several tracks with increasing black spots an another set of tracks with increasing interruptions in the information layer.
You can use them to trigger the scope better to make looking at the HF - RF depression easier. It should look like this:
Right next to the big bulge you see a nice slope, that's how it should be. If there is dent (depression) instead, than the head is not yet perfectly adjusted.
I think you can get this picture on the scope with a regular CD as well, but getting the scope to trigger correctly will be more difficult.
I don't know the exact settings of the scope to get this picture, but the time/div must be set a few clicks back and the channel must be inverted , then you must play carefully with hold-off and level settings (trigger).
Good luck!
but afterwards I found it to be very do-able.
I have the benefit of having a colleague who used to work as a service technician. He must have replaced and adjusted many laser units in his life. His advice was to ignore the official procedure described by Sony. In his experience it didn't work, use the eye-pattern instead (like many have already said).
This is what the eye pattern should look like:
An externally hosted image should be here but it was not working when we last tested it.
As you can see the 15 year old laser still does slightly better than 1 Vpp.
Play a CD and find the RF-pin. In my CD-4 there was a long row of testpins without any descriptions printed on the PCB. I just touched one pin at a time with the probe until I found the one with the eye-pattern.
The correct setting of the scope is 0.5 uS/div and 0.5 V/Div (1x probe was no problem on my player, if you use a 10x probe use the 50 mV/div setting to compensate for the 10x attenuation). The coupling should be set to AC.
The aim is to make the eye-pattern as wide as possible on the Y-axis of the scope. Start by adjusting the bal. pots (on the CD-4 they are labeled EF-bal and F-bias). When you got the eye pattern as wide as possible, chances are you can leave the gain pots alone, they are less critical. I did adjust them the way my colleague said: turn until the signal starts to drop away and then slightly back.
An added bonus was that I bought a focus-CD many years ago (never used it until now, though). On it are several tracks with increasing black spots an another set of tracks with increasing interruptions in the information layer.
You can use them to trigger the scope better to make looking at the HF - RF depression easier. It should look like this:
An externally hosted image should be here but it was not working when we last tested it.
Right next to the big bulge you see a nice slope, that's how it should be. If there is dent (depression) instead, than the head is not yet perfectly adjusted.
I think you can get this picture on the scope with a regular CD as well, but getting the scope to trigger correctly will be more difficult.
I don't know the exact settings of the scope to get this picture, but the time/div must be set a few clicks back and the channel must be inverted , then you must play carefully with hold-off and level settings (trigger).
Good luck!
OK, I have to correct myself. You can forget about the 'HF - RF depression' picture with a regular CD, I just tried. You need a (test) CD with blocked off parts to get the second picture of my previous post on the scope.
If you'd really like to check the HF - RF depression, I guess you could draw a line with a black marker across the disc (make sure to make it symmetrical or else the scope can't trigger properly).
I get the best results when the blocked off part is 0.4 mm wide and select 0.2 ms/div on the scope.
An externally hosted image should be here but it was not working when we last tested it.
If you'd really like to check the HF - RF depression, I guess you could draw a line with a black marker across the disc (make sure to make it symmetrical or else the scope can't trigger properly).
I get the best results when the blocked off part is 0.4 mm wide and select 0.2 ms/div on the scope.
Hi Jitter,
Never ignore the alignment procedure as set out in the manual! Skilled technicians can pick from methods that may work better, or be faster, but they are looking at a number of clues as they work. They can recognize when something isn't working with the procedure. If you are presented with a total read failure, the manufacturer's procedures can be a life saver. BTW, your E-F balance looks like it's out.
I recommend you glue your X1/X10 probe in the X10 position. There are two things working against you when you do this. The bandwidth of your 'scope probe is much, much lower in the X1 position. You are also loading down the circuit big time. If you hang on a buffered output, you might be okay. If you hang your probe on a high impedance point, you can upset the circuit to the point where it may run the head to the end of it's travel and break the gears. The other nifty fault is the spindle (disc) motor being run way high in speed as the motor speed control circuit loses the signal to lock onto. What often happens next is not pretty. The mechanism drop away from the CD which is rotating at a blistering rate. Next the CD may even launch itself out of the tray after spinning furiously. Those circular scars are certain to destroy a test disc, or a favorite disc. Don't do this.
The disc I use for E-F balance gives me a nice, crisp leading and trailing edge. A pattern like yours would be the answer as to why the CD player skipped so often. I have the adjustment jig for those newer Nakamichi units and I always use it. If you can not align a machine using the manual procedure, something is wrong with the machine, or the technician in 99% of the cases.
-Chris
Never ignore the alignment procedure as set out in the manual! Skilled technicians can pick from methods that may work better, or be faster, but they are looking at a number of clues as they work. They can recognize when something isn't working with the procedure. If you are presented with a total read failure, the manufacturer's procedures can be a life saver. BTW, your E-F balance looks like it's out.
No! Never, ever do that again!
I recommend you glue your X1/X10 probe in the X10 position. There are two things working against you when you do this. The bandwidth of your 'scope probe is much, much lower in the X1 position. You are also loading down the circuit big time. If you hang on a buffered output, you might be okay. If you hang your probe on a high impedance point, you can upset the circuit to the point where it may run the head to the end of it's travel and break the gears. The other nifty fault is the spindle (disc) motor being run way high in speed as the motor speed control circuit loses the signal to lock onto. What often happens next is not pretty. The mechanism drop away from the CD which is rotating at a blistering rate. Next the CD may even launch itself out of the tray after spinning furiously. Those circular scars are certain to destroy a test disc, or a favorite disc. Don't do this.
The disc I use for E-F balance gives me a nice, crisp leading and trailing edge. A pattern like yours would be the answer as to why the CD player skipped so often. I have the adjustment jig for those newer Nakamichi units and I always use it. If you can not align a machine using the manual procedure, something is wrong with the machine, or the technician in 99% of the cases.
The Denon is very similar, but there are two rows and they are labeled. You need to be very carefulk becuase tehre is alaser current test point, along with +5VDC. It's easy to shrt thesse in error and wipe out the head. I made my own jig for the Denon, and Yamaha, and Philips. It's nice to be able to just plug in and go.
Oh my!! Another home-made test CD. Your data interruption needs to be 100% opaque with sharp, clean edges. The CD itself must be free of other defects, such as poor pit shape or eccentricity. Too much trouble.
-Chris
Hi guys,
A lot of post since yesterday.
Will just add a generally reliable ( well I found it so ) way to set the tracking gain is to scope the tracking error waveform. That will be test point TE. Set the scope to a pretty low sweep speed and turn the tracking gain up. You will see a point when a low frequency "fundamental" begins to appear amongst all the servo noise. It's very definite. Just back off from this point until the fundamental is just on the point of appearing but doesn't. If you really want you can feed ( the TE signal ) to an amp and "hear" it appear.
Am sure Chris feels the same. you would just love to have 10 minutes scoping this and seeing whats going on.
One other thing. Look at the spinning disc edge on. There should be no up and down wobble. Anything much more than the thickness of a piece of paper needs investigating.
A lot of post since yesterday.
Will just add a generally reliable ( well I found it so
) way to set the tracking gain is to scope the tracking error waveform. That will be test point TE. Set the scope to a pretty low sweep speed and turn the tracking gain up. You will see a point when a low frequency "fundamental" begins to appear amongst all the servo noise. It's very definite. Just back off from this point until the fundamental is just on the point of appearing but doesn't. If you really want you can feed ( the TE signal ) to an amp and "hear" it appear.Am sure Chris feels the same. you would just love to have 10 minutes scoping this and seeing whats going on.
One other thing. Look at the spinning disc edge on. There should be no up and down wobble. Anything much more than the thickness of a piece of paper needs investigating.
@anatech:
Thanx for the constructive criticism! Dos and don'ts are always welcome.
I'm at home in (industrial) electronics, preferably analogue, but mechanical parts are not my strong point. Probably why I've had the Focus-CD lying around for years before I felt confident enough to actually use it (and probably also because adjustment was not needed previously).
I must say that I hadn't considered the limited bandwith of a 1x probe. My specialty, at work, is calibrating and testing analogue measuring equipment. The bulk of the adjustments and tests are done with the use DC signals and only some LF.
I take it you are referring to the pictures (a certain one in particular?). The player works fine, no skipping, not even on somewhat degraded CD-Rs. Maybe the picture doesn't look very nice because the camera I used had trouble focusing and needed a rather long shutter time. Chances are the trace on the scope looks more blurred on the picture than in real life. Or is it something else you're looking at? Please tell...
Thanx for the constructive criticism! Dos and don'ts are always welcome.
I'm at home in (industrial) electronics, preferably analogue, but mechanical parts are not my strong point. Probably why I've had the Focus-CD lying around for years before I felt confident enough to actually use it (and probably also because adjustment was not needed previously).
I must say that I hadn't considered the limited bandwith of a 1x probe. My specialty, at work, is calibrating and testing analogue measuring equipment. The bulk of the adjustments and tests are done with the use DC signals and only some LF.
I take it you are referring to the pictures (a certain one in particular?). The player works fine, no skipping, not even on somewhat degraded CD-Rs. Maybe the picture doesn't look very nice because the camera I used had trouble focusing and needed a rather long shutter time. Chances are the trace on the scope looks more blurred on the picture than in real life. Or is it something else you're looking at? Please tell...
Hi Mooly,
You know it!
I am in complete agreement with you. I just want to caution DIYers that trained technicians know a great deal. What we do only looks easy and we prove our worth when things do not go according to plan. There are a ton of things we do subconsciously, so it appears that steps missed are not required. This is the same for all skilled trades.
Hi jitter,
Cool.
I used to work in a calibration lab for industrial and lab type instruments. While calibrating using BNC connectors, you are terminated properly. This preserves the bandwidth. Notice that BNC stuff normally terminates with a 50 ohm load. The X10 probe uses a trimmer capacitor to compensate for the capacitance after the dropping resistor. It also greatly reduces the loading capacitance.
I was referring to your last screen shot, probably around 0.5mS / div. I set up that way often to set up E-F balance. Triggering is a pain to get right. Try that with a DSO (I have, it seems to be more difficult to get a good display). Your focus is not the issue. I'll have to find a shot of this, or we'll have to wait for the next CD player I do.
-Chris
You know it!
I am in complete agreement with you. I just want to caution DIYers that trained technicians know a great deal. What we do only looks easy and we prove our worth when things do not go according to plan. There are a ton of things we do subconsciously, so it appears that steps missed are not required. This is the same for all skilled trades.
Hi jitter,
Cool.
I used to work in a calibration lab for industrial and lab type instruments. While calibrating using BNC connectors, you are terminated properly. This preserves the bandwidth. Notice that BNC stuff normally terminates with a 50 ohm load. The X10 probe uses a trimmer capacitor to compensate for the capacitance after the dropping resistor. It also greatly reduces the loading capacitance.
I was referring to your last screen shot, probably around 0.5mS / div. I set up that way often to set up E-F balance. Triggering is a pain to get right. Try that with a DSO (I have, it seems to be more difficult to get a good display). Your focus is not the issue. I'll have to find a shot of this, or we'll have to wait for the next CD player I do.
-Chris
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