Hello everyone,
I am kindly asking for advice in mechanical alignment of CDM-1 swing arm. I disassembled spindle motor and swing arm for cleaning and lubricating. After re-assembling, the unit works well. However, the focus voltage is not constant from center to the edge of disc, which probably means that the laser does not move parallel to the disc surface.
Has anyone performed a successful mechanical alignment as described in the service manual? If so, what accessories do you use instead of special mirror and a glass CD? Also, instead of optical alignment, would it be possible to align the swing arm by measuring focus voltage ad beginning and end of disc and bringing them close enough?
One last question: with an obviously misaligned transport as mine, what should be the permissible focus voltage range and should I expect weaker tracking and slower track skipping speed at the end of CD?
Thank you in advance.
I am kindly asking for advice in mechanical alignment of CDM-1 swing arm. I disassembled spindle motor and swing arm for cleaning and lubricating. After re-assembling, the unit works well. However, the focus voltage is not constant from center to the edge of disc, which probably means that the laser does not move parallel to the disc surface.
Has anyone performed a successful mechanical alignment as described in the service manual? If so, what accessories do you use instead of special mirror and a glass CD? Also, instead of optical alignment, would it be possible to align the swing arm by measuring focus voltage ad beginning and end of disc and bringing them close enough?
One last question: with an obviously misaligned transport as mine, what should be the permissible focus voltage range and should I expect weaker tracking and slower track skipping speed at the end of CD?
Thank you in advance.
I've never used the official method either and tbh have never looked at equalising the focus voltage but yes, doing that should be an accurate way of ensuring the arm is parallel to the disc. It has to be, the DC bias determines the position of the lens (focus coil). I've no idea off hand what the typical average DC focus voltage would be, only to say that it will have a wide range of values that will work. The platter height will be the main factor with the swing arm at the start position so if that has not been disturbed then I would take that as a "normal" value.
I suppose tracking ability does vary at disc edge due to the combined mechanical/electrical characteristics of the complete servo being different at disc start and disc end. A good test would be the official Philips playability discs with simulated errors.
Edit... what I would definitely look at is the quality of the RF at start and finish and make sure that there is no change in quality or amplitude.
I suppose tracking ability does vary at disc edge due to the combined mechanical/electrical characteristics of the complete servo being different at disc start and disc end. A good test would be the official Philips playability discs with simulated errors.
Edit... what I would definitely look at is the quality of the RF at start and finish and make sure that there is no change in quality or amplitude.
Hello Mooly and thanks for your opinion.
Today I have attempted the optical alignment procedure with a transparent CD and looking at the lens at an angle which actually gives reflection, as I don't have an appropriate mirror to put on. Spanning a string across a light above the lens will cast a thin but sharp shadow.
I am now confused because the distance between the two reflections which should be brought to a single line (from CD and lens) actually varies with the distance of string from the transport.
Any advice?
Today I have attempted the optical alignment procedure with a transparent CD and looking at the lens at an angle which actually gives reflection, as I don't have an appropriate mirror to put on. Spanning a string across a light above the lens will cast a thin but sharp shadow.
I am now confused because the distance between the two reflections which should be brought to a single line (from CD and lens) actually varies with the distance of string from the transport.
Any advice?
I'm afraid I've nothing useful to add really. The string and transparent disc (where do you get a transparent disc from ? A blank from a pack of CDR/DVDR etc 
) is one of those things you would have to see in operation to get a feel for what its telling you. I can't quite visualise it tbh, and I'm thinking that as the arm traverses an arc then it will deviate from a line cast by the shadow of a taught string... but I guess you don't mean that.
) is one of those things you would have to see in operation to get a feel for what its telling you. I can't quite visualise it tbh, and I'm thinking that as the arm traverses an arc then it will deviate from a line cast by the shadow of a taught string... but I guess you don't mean that.
Yep.Philips were often fanatical in some of their alignment procedures (TV/ video to) and technicians always worked around them or devised their own workarounds.
Unless you have a problem with playability or can see the RF quality as non consistent between start and finish on the disc then I wouldn't worry.
Here is my contribution to the knowledge base on how to align the swing arm assembly within satisfactory tolerances using the method of minimizing the focus voltage offset across the CD. No reference discs or tools are required.
It is absolutely not necessary to make this adjustment if the factory alignment has not been disturbed. In my case, alignment was required because I had disassembled, cleaned and lubricated swing arm and disc motor and voltage offsets were exceeding 1V afterwards.
I tried the optical alignment described in Philips' service manual. However, it is simply too sensitive and transparent plastic CDs from a CD-R pack, suggested by several sources as a replacement for reference glass disc, are not suitable as they are wavy and can give erroneous parallaxes from different angles.
I used 10 different pressed CDs from my collection (I did not use CD-Rs). They need to be as flat as possible and you can observe if they are wavy by looking at the reflection on their top sides near the edge. For every disc, I measured the offset voltage value at beginning and at 50:00 minute mark (thus measuring the latter at the same distance from the disc center) and put the data in a small Excel table. I calculated the average offset for the series which was around 800mV. As a side note, you will discover that there are factory CDs of all kinds: with small offsets, huge offsets, falling and rising offsets across (therefore reflective surfaces at different angles), and so on, but this has no importance, whatsoever.
Next step was to pick the CD with biggest offset from the series and adjust the swing arm to minimize the offset as much as possible. To do this, unfasten the two Torx screws which hold the shin so that it can move but do not loosen them completely. Position the player horizontally and allow access to the transport form bottom side - I used two chairs set apart a little. The swing arm shin has only a few mm play on X and Y axis and has to be moved very gently and gradually. By trial and error, adjustment will also cause the laser to completely fall out from focus and reproduction but in the end I was able to greatly reduce the offset on that CD.
Next step was to measure offsets for other CDs and compare new values with old ones - note that here the start and 50:00 values will have changed but they are not important at this step, the goal is to see that offset differences on all discs are reduced after the alignment. By measuring all CDs and adding the data to the Excel table, this is likely the result you will have attained. In my case, the attained average offset went down from 800mV to 197mV. This is a satisfactory result and the screws can be fastened, taking great care that the shin remains in adjusted place and is not moved. Make sure that you did not disturb the alignment by measuring offset on one CD again.
It is very important to check that swing arm moves absolutely freely after the alignment: when flicked with finger, it should bounce back and forth a few times. Any stiffer than this and you might have tracking difficulty and problems in operation. Even the Philips service manual clearly states that the swing arm alignment is a compromise between optical adjustment and easily moving assembly. Lubrication will not improve movement of a misaligned swing arm. Also, use neutral oil to lubricate in order to preserve the small MBR O-rings which enclose ball bearings on the axis. A worthwhile check of swing arm movement is to put the player in service mode and check its deflection on various steps as described in player's own service manual. This can be compensated by adjusting radial motor offset in +/-100mV range.
As a final step, height of the disc motor should be re-adjusted by turning the bottom spindle bearing. I went back to the Excel table and calculated the value which would ensure equal average offset against zero value. That is, a theoretical CD which would be the average of chosen 10 CDs, should have equalized offset in + and - range. By doing so, you will avoid that the player operates mostly in + or - offset range. To illustrate in concrete numbers:
VALUES AFTER ALIGNMENT
Average offset 00:00 = -200mV
Average offset 50:00 = -400mV
Average offset difference = -200mV
Therefore, the offset difference should move between +100mV and -100mV. Therefore:
New average offset 00:00 = 100mV
New average offset 50:00 = -100mV
Average offset difference remains the same.
The difference between old and new offset is +300mV. Select any of chosen 10 CDs, add 300mV to the measured 00:00 offset and adjust height of the disc motor to that value. Secure the spindle bearing with lacquer and the procedure is over.
I hope this helps. Please feel free to comment or correct if you find any error in described procedure.
It is absolutely not necessary to make this adjustment if the factory alignment has not been disturbed. In my case, alignment was required because I had disassembled, cleaned and lubricated swing arm and disc motor and voltage offsets were exceeding 1V afterwards.
I tried the optical alignment described in Philips' service manual. However, it is simply too sensitive and transparent plastic CDs from a CD-R pack, suggested by several sources as a replacement for reference glass disc, are not suitable as they are wavy and can give erroneous parallaxes from different angles.
I used 10 different pressed CDs from my collection (I did not use CD-Rs). They need to be as flat as possible and you can observe if they are wavy by looking at the reflection on their top sides near the edge. For every disc, I measured the offset voltage value at beginning and at 50:00 minute mark (thus measuring the latter at the same distance from the disc center) and put the data in a small Excel table. I calculated the average offset for the series which was around 800mV. As a side note, you will discover that there are factory CDs of all kinds: with small offsets, huge offsets, falling and rising offsets across (therefore reflective surfaces at different angles), and so on, but this has no importance, whatsoever.
Next step was to pick the CD with biggest offset from the series and adjust the swing arm to minimize the offset as much as possible. To do this, unfasten the two Torx screws which hold the shin so that it can move but do not loosen them completely. Position the player horizontally and allow access to the transport form bottom side - I used two chairs set apart a little. The swing arm shin has only a few mm play on X and Y axis and has to be moved very gently and gradually. By trial and error, adjustment will also cause the laser to completely fall out from focus and reproduction but in the end I was able to greatly reduce the offset on that CD.
Next step was to measure offsets for other CDs and compare new values with old ones - note that here the start and 50:00 values will have changed but they are not important at this step, the goal is to see that offset differences on all discs are reduced after the alignment. By measuring all CDs and adding the data to the Excel table, this is likely the result you will have attained. In my case, the attained average offset went down from 800mV to 197mV. This is a satisfactory result and the screws can be fastened, taking great care that the shin remains in adjusted place and is not moved. Make sure that you did not disturb the alignment by measuring offset on one CD again.
It is very important to check that swing arm moves absolutely freely after the alignment: when flicked with finger, it should bounce back and forth a few times. Any stiffer than this and you might have tracking difficulty and problems in operation. Even the Philips service manual clearly states that the swing arm alignment is a compromise between optical adjustment and easily moving assembly. Lubrication will not improve movement of a misaligned swing arm. Also, use neutral oil to lubricate in order to preserve the small MBR O-rings which enclose ball bearings on the axis. A worthwhile check of swing arm movement is to put the player in service mode and check its deflection on various steps as described in player's own service manual. This can be compensated by adjusting radial motor offset in +/-100mV range.
As a final step, height of the disc motor should be re-adjusted by turning the bottom spindle bearing. I went back to the Excel table and calculated the value which would ensure equal average offset against zero value. That is, a theoretical CD which would be the average of chosen 10 CDs, should have equalized offset in + and - range. By doing so, you will avoid that the player operates mostly in + or - offset range. To illustrate in concrete numbers:
VALUES AFTER ALIGNMENT
Average offset 00:00 = -200mV
Average offset 50:00 = -400mV
Average offset difference = -200mV
Therefore, the offset difference should move between +100mV and -100mV. Therefore:
New average offset 00:00 = 100mV
New average offset 50:00 = -100mV
Average offset difference remains the same.
The difference between old and new offset is +300mV. Select any of chosen 10 CDs, add 300mV to the measured 00:00 offset and adjust height of the disc motor to that value. Secure the spindle bearing with lacquer and the procedure is over.
I hope this helps. Please feel free to comment or correct if you find any error in described procedure.
This is an old thread but I just want to add some info on the alignment which should be useful to other.
I've bought a working CD-304 MKII from eBay Germany. But unfortunately the seller didn't have the shipping screws to lock down the CDM-1 mechanism, and the handling during shipment was very rough. When it arrived the swing arm couldn't move to the outer region. Actually, part of the aluminium diecast case was broken off that block the path of the swing arm slightly. It should be an easy fix by bending the case back but before I could see that I've disassembled the swing arm, thinking it was knocked out of alignment. So I need to do the alignment procedure.
I've read the service manual of CDM-0 (english) and CDM-1 (dutch), but couldn't understand the procedure and of course I didn't have the mirror and glass disc. Fortunately there is an website with the procedure outlined:
CDM1 Laser Winkel einstellen (germany)
It shows using a transparent CD-R that usually comes with a 50 disc bulk pack (the last disc). I drew a straight, thin black line on the CD at approximate midway from center to outer rim. I also think that the top of the lens is flat, so I just use the reflection off the top of the lens to do the alignment (no need to use a mirror).
The service manual ask you to use a fluorescent tube with grid. In my room the illumination is a long, straight fluorescent tube, I just drew a thick black line on the tube itself. (The line in the reflection will be much thinner so you need to draw it thicker, otherwise it will be difficult to see.) I didn't use a ruler, just a rough straight line is good enough (it is much minimize in size in the reflection, so the error of it is much smaller.)
The procedure itself:
1. Working directly beneath the fluorescent tube (FLT). Position yourself and the CDM, so that you are always looking along the axis of the FLT, as shown by the service manual (SM).
2. Put the transparent CD on the CDM, turn it so that the black line roughly pass through the center of the swing arm axis of rotation, like the SM or the webpage. Now turn the whole CDM so the reflection of the FLT on the CD is parallel to the black line on the CD.
3. position the lens of the swing arm (SW ARM) to be under the line on the CD.
4. Now, looking at the reflection of the FLT on the CD, carefully position your head and the CDM, so that the black line on the CD is coaxial with the black line on the FLT!
I mean on the CD surface, the black line on FLT (it is virtual image, of the line you draw on the FLT) is overlapping with the black line on the CD (it is the physical line you draw on the CD). To do so your eye must be on the same plane that both axes the your drawn lines pass through and your line of sight is also looking along this plane. This requirement set your eye up as a testing equipment to check the alignment of the SW ARM lens.
5. FIX your body and your eye at this position! Now carefully look at the reflection of the FLT on the top of the lens of the SW ARM, and see if the thick line on the FLT is also coaxial with the thin line on the CD. Because the reflection off the lens is a bit weak, you may have move your head along the plane of the lines back and forth to see a stronger reflection. BUT you must keep the condition in 4. This is the price your pay for without a perfectly flat mirror.
6. The SM states that if the line on the reflection of the SW ARM is not coaxial with the lines on CD (and FLT since they are coaxial during the examination,) the error must be less than 4mm. I certainly want to do better than that. So untighten the two screws of the SW ARM and shift the bearing plane slightly, and then recheck with the above procedure.
7. If it is OK, turn the CD to roughly 90 degree clockwise to previous position, so that the line on CD cross over the SW ARM lens again, as shown in te SM and the webpage. Repeat the above procedure 1-6.
8. You need to check these two position back and forth, so that the SW ARM lens is truely parallel to the plan of the CD.
9. The SM actually shows you how you should shift the bearing plate when the image of the line on the SW ARM is shifted to one line for these two checking positions. But you need to do this yourself to see what it is trying to tell you.
The movement of the bearing plane is very limited, so you shouldn't take too many time to arrive alignment.
The quality of the transparent CDR is not very high, as shown by local deformation of the reflection of the straight. But it is not very important as long as it shows you an overall straight line but it does limit the accuracy you can achieve. But you should know that getting optically flat glass disc and mirror is not cheap. It definitely worked for me without any serious money outlay.
Regards,
Edward Tam
I've bought a working CD-304 MKII from eBay Germany. But unfortunately the seller didn't have the shipping screws to lock down the CDM-1 mechanism, and the handling during shipment was very rough. When it arrived the swing arm couldn't move to the outer region. Actually, part of the aluminium diecast case was broken off that block the path of the swing arm slightly. It should be an easy fix by bending the case back but before I could see that I've disassembled the swing arm, thinking it was knocked out of alignment. So I need to do the alignment procedure.
I've read the service manual of CDM-0 (english) and CDM-1 (dutch), but couldn't understand the procedure and of course I didn't have the mirror and glass disc. Fortunately there is an website with the procedure outlined:
CDM1 Laser Winkel einstellen (germany)
It shows using a transparent CD-R that usually comes with a 50 disc bulk pack (the last disc). I drew a straight, thin black line on the CD at approximate midway from center to outer rim. I also think that the top of the lens is flat, so I just use the reflection off the top of the lens to do the alignment (no need to use a mirror).
The service manual ask you to use a fluorescent tube with grid. In my room the illumination is a long, straight fluorescent tube, I just drew a thick black line on the tube itself. (The line in the reflection will be much thinner so you need to draw it thicker, otherwise it will be difficult to see.) I didn't use a ruler, just a rough straight line is good enough (it is much minimize in size in the reflection, so the error of it is much smaller.)
The procedure itself:
1. Working directly beneath the fluorescent tube (FLT). Position yourself and the CDM, so that you are always looking along the axis of the FLT, as shown by the service manual (SM).
2. Put the transparent CD on the CDM, turn it so that the black line roughly pass through the center of the swing arm axis of rotation, like the SM or the webpage. Now turn the whole CDM so the reflection of the FLT on the CD is parallel to the black line on the CD.
3. position the lens of the swing arm (SW ARM) to be under the line on the CD.
4. Now, looking at the reflection of the FLT on the CD, carefully position your head and the CDM, so that the black line on the CD is coaxial with the black line on the FLT!
I mean on the CD surface, the black line on FLT (it is virtual image, of the line you draw on the FLT) is overlapping with the black line on the CD (it is the physical line you draw on the CD). To do so your eye must be on the same plane that both axes the your drawn lines pass through and your line of sight is also looking along this plane. This requirement set your eye up as a testing equipment to check the alignment of the SW ARM lens.
5. FIX your body and your eye at this position! Now carefully look at the reflection of the FLT on the top of the lens of the SW ARM, and see if the thick line on the FLT is also coaxial with the thin line on the CD. Because the reflection off the lens is a bit weak, you may have move your head along the plane of the lines back and forth to see a stronger reflection. BUT you must keep the condition in 4. This is the price your pay for without a perfectly flat mirror.
6. The SM states that if the line on the reflection of the SW ARM is not coaxial with the lines on CD (and FLT since they are coaxial during the examination,) the error must be less than 4mm. I certainly want to do better than that. So untighten the two screws of the SW ARM and shift the bearing plane slightly, and then recheck with the above procedure.
7. If it is OK, turn the CD to roughly 90 degree clockwise to previous position, so that the line on CD cross over the SW ARM lens again, as shown in te SM and the webpage. Repeat the above procedure 1-6.
8. You need to check these two position back and forth, so that the SW ARM lens is truely parallel to the plan of the CD.
9. The SM actually shows you how you should shift the bearing plate when the image of the line on the SW ARM is shifted to one line for these two checking positions. But you need to do this yourself to see what it is trying to tell you.
The movement of the bearing plane is very limited, so you shouldn't take too many time to arrive alignment.
The quality of the transparent CDR is not very high, as shown by local deformation of the reflection of the straight. But it is not very important as long as it shows you an overall straight line but it does limit the accuracy you can achieve. But you should know that getting optically flat glass disc and mirror is not cheap. It definitely worked for me without any serious money outlay.
Regards,
Edward Tam
Last edited:
The same website also show you how to deal with the spindle motor bearing
CDM1 Motor
My motor could hardly start, due to the bearing is worn down so that is a hole on its surface. Since the magnetic force is stronger with decreasing distance and the contact surface of the axis and the bearing is now bigger, the friction increase. I didn't want to grind down the bearing like the webpage, so I add a drop of epoxy to fill up the hole. Then I add a thin layer of teflon on top (~0.5mm). The bearing near to be backed off a bit to bring the turntable back to its original height. But it works. And if the teflon is worn out, I can just add another piece again.
CDM1 Motor
My motor could hardly start, due to the bearing is worn down so that is a hole on its surface. Since the magnetic force is stronger with decreasing distance and the contact surface of the axis and the bearing is now bigger, the friction increase. I didn't want to grind down the bearing like the webpage, so I add a drop of epoxy to fill up the hole. Then I add a thin layer of teflon on top (~0.5mm). The bearing near to be backed off a bit to bring the turntable back to its original height. But it works. And if the teflon is worn out, I can just add another piece again.
Hello, kf_tam,
so you basically followed the service manual, minus the mirror on laser lens. Good to know it can be done with sufficient precision without. Did you adjust all the player parameters by measuring points and is the player working happily now (no radial motor strain, no noisy operation, etc.)? If the die cast chassis was broken, I think you should be happy that the transport works at all. And, by the way, it has nothing to do with transport screws which only immobilize the swing arm, but wih rough freight.
so you basically followed the service manual, minus the mirror on laser lens. Good to know it can be done with sufficient precision without. Did you adjust all the player parameters by measuring points and is the player working happily now (no radial motor strain, no noisy operation, etc.)? If the die cast chassis was broken, I think you should be happy that the transport works at all. And, by the way, it has nothing to do with transport screws which only immobilize the swing arm, but wih rough freight.
I think the mechanical adjustment is meant for the assembly line, so that the unit did not need to be integrated in the servo circuit, and could be adjusted independently. Perhaps the CDM1 was produced at a different manufacturing plant. The servo voltage method seems easier for us poor consumers.
To my observation the transport screws "only" secure the whole mechanism
which sits on rather stiff rubber dampers.
Bur the clamper is pressed on the disc table by a stiff frame that is
not connected to the mech but the player´s frame.
Maybe this is why the mech is secured and lowered by the transport screws a bit.
BTW, did anyone clean the RAFOC like shown by this guy?
CDM-1 is described on the bottom of the page.
http://www.lampizator.eu/LAMPIZATOR/TRANSPORT/laser/Laserology.html
Still looking for CDM-1 with dead laser - want to evaluate on replacing the Diode.
which sits on rather stiff rubber dampers.
Bur the clamper is pressed on the disc table by a stiff frame that is
not connected to the mech but the player´s frame.
Maybe this is why the mech is secured and lowered by the transport screws a bit.
BTW, did anyone clean the RAFOC like shown by this guy?
CDM-1 is described on the bottom of the page.
http://www.lampizator.eu/LAMPIZATOR/TRANSPORT/laser/Laserology.html
Still looking for CDM-1 with dead laser - want to evaluate on replacing the Diode.
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Sory, there is an error in my previous post:
Cleaning the lens in this link
Laserology
shows CDM-1MKII / CDM-2 not CDM-1. Very different from CDM-1.
Cleaning the lens in this link
Laserology
shows CDM-1MKII / CDM-2 not CDM-1. Very different from CDM-1.
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