Hi deadpool,
It costs the customer more in labour to replace the motor compared to the head for one.
I've trained techs for years and came into CDs on the ground floor being trained by everyone (but Sony). Philips, Yamaha and Marantz were big into training, as was Denon. One thing that made sense was that you always gain as much information from the unit as possible before doing anything. Same as any other repair type. I get repairs from other techs all the time that are stuck and the one thing they have in common is that they changed parts without troubleshooting. With motors, many get the height wrong. Whenever you do something, the possibility exists to create another problem.
Besides, it doesn't take very long to perform some easy tests. Looking at the eye pattern and measuring Iop is easy. That can lead you directly to a motor, or a head that is drawing over 10% higher in current than the Iop (the head is then deemed to be past its useful life and replacement is justified).
Compare that to replacing the motor and then having to troubleshoot anyway - except now you have introduced a variable. I trained my guys to always know what is bad and be able to justify that to any customer. I am very pro-customer, especially with the cost of some of these parts. Remember, you are spending their money.
-Chris
It costs the customer more in labour to replace the motor compared to the head for one.
I've trained techs for years and came into CDs on the ground floor being trained by everyone (but Sony). Philips, Yamaha and Marantz were big into training, as was Denon. One thing that made sense was that you always gain as much information from the unit as possible before doing anything. Same as any other repair type. I get repairs from other techs all the time that are stuck and the one thing they have in common is that they changed parts without troubleshooting. With motors, many get the height wrong. Whenever you do something, the possibility exists to create another problem.
Besides, it doesn't take very long to perform some easy tests. Looking at the eye pattern and measuring Iop is easy. That can lead you directly to a motor, or a head that is drawing over 10% higher in current than the Iop (the head is then deemed to be past its useful life and replacement is justified).
Compare that to replacing the motor and then having to troubleshoot anyway - except now you have introduced a variable. I trained my guys to always know what is bad and be able to justify that to any customer. I am very pro-customer, especially with the cost of some of these parts. Remember, you are spending their money.
-Chris
This matches my experience from 25 years ago when I operated an audio/video repair shop. I recall frequently purchasing CD spindle motors in lots of 10-25 pieces. Even today as a semi-retired collector/restorer I keep a selection of spindle motors on hand.
Regarding my recent Sony CDP-C305 restoration, I suspect its sled drive motor failure was precipitated by the (extremely) dirty detector switch for signaling the MCU that the sled is in the “home” position. Unfortunately the MCU keeps the sled motor powered indefinitely if the switch fails to close. The motor shoves the sled against its physical stop and then stalls. When stalled the motor current is 200-300mA vs. only 20-50mA when rotating. In the Sony CDP-C305 a faulty “home position” detector switch also prevents the disc tray from opening.
Spindle motors & sled drive motors can be tested with a DC power source of 4-6V and a mA meter. The motor must be permitted to spin freely for this test. Therefore sled drive motors need to be dismounted from the mechanism or one of the gears in the drive train temporarily removed. Motor current under no-load condition is typically no more than 25-30mA. Also check that motor current and RPM is similar for both directions of rotation by reversing the DC power polarity.
If a variable DC power supply is available then the minimum voltage to get the motor to begin rotating can also be checked. This is typically 0.5 to 0.9 volts. A good motor will rotate smoothly in both directions at a very low speed. A faulty motor will tend to stall at one position and require >1.5-2V to get it to start.
I think the actual failure mechanism is often from conductive debris lodged in the slot between two adjacent commutator bars. This partially shorts one pole of the armature winding and creates excessive “electromagnetic” drag.
-EB
The spindle motor on the original factory fit Philips CDM12.4's had a little plastic (think it was plastic) spring that lightly pressed onto the spindle, presumably to try and stop any bearing jitter. It was very light acting but I always wondered if it might wear the bearing in an oval shape. CDM12.1's never had the pleasure of that spring as I recall.
Sony also did something similar in their DVP-NS series of DVD/CD/SACD players made from 2002-2004. This series of machines includes their legendary DVP-NS999ES.
There is a tiny nylon bobbin (dropped over the spindle motor shaft below the disc platter) which rotates freely on the motor shaft. And there is a thin spring-steel wire which presses against the inside of the plastic bobbin. This generates a few grams of side load on the vertical spindle motor shaft. This prevents the shaft from wobbling even if the bearing is slightly loose or the disc is out of balance. It reminds me of how (in the analog vinyl disc world) a belt-drive turntable often sounds more “solid” (to me) than a direct drive turntable. This is because the side-load of the belt reduces shaft/bearing wobble.
It seems curious that Philips did this in their CDM12 mechanisms which often get criticized for being “cheap and poorly made.”
I think a similar “side loading” modification could be made to almost any CD transport.
When I get a chance I’ll post close-up photos of Sony’s implementation as used in their DVP-NS series.
-EB
I totally agree with Chris here. Diagnose first. Then replace whats’ broken.
I am also willing to swap sub-assemblies and PC boards between identical units in order to help pinpoint where a fault is located. For me there’s nothing better than having 4 or 5 identical (or nearly identical) units on the bench together to compare with each other.
-EB
I moved the restored Denon DCM-320 5-disc CD changer upstairs into my den area. It is connected to a little Bose “wave radio” at the moment. Even with such modest amplification and speakers I am blown away by how much “music” comes out of this DCM-320. This can be heard even at background listening levels.
As an EE with an advanced degree and a thorough understanding of DAC circuitry, op-amps, jitter, distortion, etc., I am at a loss to explain why this machine sounds so damn good. It’s gonna be hard to part with this one. My goal was to reduce my horde of vintage CD players by at least 10 units. It will be easy to sell all the Sony units. Yes, the Sony CD players do sound better than an MP3 from my Android device connected via Bluetooth, but this Denon is in a whole different universe. I’m impressed. The engineers at Denon did good work. Along these lines I’m eager to get the Denon DCD-1500II I bought last month into rotation in my main audio system.
-EB
The 12.4 was originally developed for CD ROM use as well as just audio and so a low error rate was a requirement. The cooking grade 12.1 did not get this refinement.
The original Philips 12.4's were pretty good imo once you had stripped them down to fix the 'grease' issue that was the cause of most complaints and failures. It used to get little hard gritty nodules in it, like grains of sugar and they jammed the gears on the sled.
Most replacement 12.4's (if they were not Philips) were junk although there were some rare Japanese made 12.4's at one time and they were outstanding.
Need to thank the OP so much!
I own a Sony CDP-M72 since it came out like 30 years ago and have been suffering the "returning tray" issue since.... I don't know.... 20 years maybe? Only until I stomped on this, opened the thing, and found out mine is identical inside!
Stole iso and high vacuum grease from the lab, followed the instructions, and like new!! Couldn't be more happy!
BTW, I also saw a few beautiful Elna capacitors. They were looking like new, but after so long... do these things need to be replaced like in amps? Or if it works, better don't touch...
I own a Sony CDP-M72 since it came out like 30 years ago and have been suffering the "returning tray" issue since.... I don't know.... 20 years maybe? Only until I stomped on this, opened the thing, and found out mine is identical inside!
Stole iso and high vacuum grease from the lab, followed the instructions, and like new!! Couldn't be more happy!
BTW, I also saw a few beautiful Elna capacitors. They were looking like new, but after so long... do these things need to be replaced like in amps? Or if it works, better don't touch...
Hi Mooly,
I just registered with diyAudio and this thread has been very helpful to me. Thanks !
I'm cleaning and lubricating a Denon DCD-1420 that I've owned since new in 1989 and has worked flawlessly until recently. It has the original KSS-150 and mechanism.
It has started to skip every once in a while, sometimes just missing a beat but also sometimes skipping quite erratically 30 - 40 seconds forward or backward.
After doing some searching online I concluded this might be due to dried up and clogged lubricant on various parts of the mechanism. So I opened it up (for the first time ever) and found indeed that the white lithium grease on the metal rail that guides the laser did indeed have some clogs and dirt on it. The grease had also turned kind of yellow instead of white.
After removing the laser and upon further inspection I found that the grease on the gear wheel under the sled, the cogs on the sled motor spindle and the teethed black plastic guide rail attached to the laser all looked pretty dry as well. So I cleaned everything with isopropyl and sparsely re-lubricated all parts with white lithium grease.
Now I am a bit confused. At the beginning of this thread you mention not to lubricate any teeth on gear wheels. That they're supposed to be clean and dry. Any particular reason why ? I'm just curious because there was lithium grease everywhere I can see teeth in my player.
I was looking at one of the pictures you posted in the restoration project and I can see white grease as well on teethed rail next to the laser and the white gear wheel underneath :
So forgive me my ignorance but am I missing something here ?
I just registered with diyAudio and this thread has been very helpful to me. Thanks !
I'm cleaning and lubricating a Denon DCD-1420 that I've owned since new in 1989 and has worked flawlessly until recently. It has the original KSS-150 and mechanism.
It has started to skip every once in a while, sometimes just missing a beat but also sometimes skipping quite erratically 30 - 40 seconds forward or backward.
After doing some searching online I concluded this might be due to dried up and clogged lubricant on various parts of the mechanism. So I opened it up (for the first time ever) and found indeed that the white lithium grease on the metal rail that guides the laser did indeed have some clogs and dirt on it. The grease had also turned kind of yellow instead of white.
After removing the laser and upon further inspection I found that the grease on the gear wheel under the sled, the cogs on the sled motor spindle and the teethed black plastic guide rail attached to the laser all looked pretty dry as well. So I cleaned everything with isopropyl and sparsely re-lubricated all parts with white lithium grease.
Now I am a bit confused. At the beginning of this thread you mention not to lubricate any teeth on gear wheels. That they're supposed to be clean and dry. Any particular reason why ? I'm just curious because there was lithium grease everywhere I can see teeth in my player.
I was looking at one of the pictures you posted in the restoration project and I can see white grease as well on teethed rail next to the laser and the white gear wheel underneath :
So forgive me my ignorance but am I missing something here ?
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Some manufacturers do smoother everything in grease. If you look at the tray assembly on the Sony you will see that any grease on the gears would migrate easily onto both the area where the belt is (causing future problems) and also onto the underside of the tray itself. The gears on tray also rotate very quickly and that 'spins' the grease outward adding to the problems. Also depending on the environment it can soon gather and cause dust and fluff on the tray understand to stick. The grease applied sparingly on the large plastic spindles does serve a purpose though in making the tray smooth and slick in operation.
The grease on the pickup sled/gears/rails is a different matter. The large white gear spins only relatively slowly even when moving the pickup from end to end and so there is no danger of spin off of the grease. It also serves the very important function of damping any backlash in the gears. The gears are not cut fine or precisely enough to prevent slight movement to and fro and here the grease helps damp that effect. It also helps protect the teeth should a damaged disc be inserted and the servo fails to lock. The player can end up forcing the sled to the end stops where the sled motor continues to rotate but the large nylon gear then 'slips' on the teeth on the rack on the pickup. The grease offers protection when that happens.
Any grease used has to be plastics/metal compatible and of suitable viscosity.
Edit... images like this
How to attach images to your posts.
The grease on the pickup sled/gears/rails is a different matter. The large white gear spins only relatively slowly even when moving the pickup from end to end and so there is no danger of spin off of the grease. It also serves the very important function of damping any backlash in the gears. The gears are not cut fine or precisely enough to prevent slight movement to and fro and here the grease helps damp that effect. It also helps protect the teeth should a damaged disc be inserted and the servo fails to lock. The player can end up forcing the sled to the end stops where the sled motor continues to rotate but the large nylon gear then 'slips' on the teeth on the rack on the pickup. The grease offers protection when that happens.
Any grease used has to be plastics/metal compatible and of suitable viscosity.
Edit... images like this
How to attach images to your posts.
I use this. Post #236 and #238
Sony CDP790 and KSS240 Restoration Project
Sony CDP790 and KSS240 Restoration Project
Sony CDP790 and KSS240 Restoration Project
Sony CDP790 and KSS240 Restoration Project
I have Arcam cd72 on the table. It has problem that skips or often have difficulty with Toc reading. I want to by new optical pickup but after clossely look o found out that white plastic sled for optical pickup is cracked on 3points. On this points skips. I tried to find kss240 complete mechanism but no luck. Any help? Thank you.
Hi androa76,
If you look at different mechanisms, you may find one with the same plate chassis for a different head. What you are describing was very common.
The fact is, the player is junk without a replacement transport. I have heard of someone printing a new plastic piece but I do not know how that turned out.
-Chris
If you look at different mechanisms, you may find one with the same plate chassis for a different head. What you are describing was very common.
The fact is, the player is junk without a replacement transport. I have heard of someone printing a new plastic piece but I do not know how that turned out.
-Chris
Hello,
I have just registered with diyAudio after finding this thread while searching for information on a problem with my Myryad MCD-500 which has a KSS240a mechanism.
The disc will load and begin to play with no issues, somewhere past the half way point, quite a bit of static starts in the playback. The best way I can describe the sound, is like a radio station that's not tuned properly. If I begin playback at a track past half way point the static starts almost immediately.
I removed, cleaned and lubricated the mechanism based on advice in this very helpful thread, which solved my problem for about 3 discs,
I also noticed the during playback with the cover removed the top clamp appeared to start wobbling slightly as head advanced through playback. By top clamp I mean the disk which is part of the black plastic piece that holds the loading tray in place.
When I saw androa76's post about cracks in the plastic sled, I took a second look at mine and counted 6 hair line cracks from front to back. But, I do not have any skipping or TOC reading problems.
Any suggestions or advice?
Thank you
I have just registered with diyAudio after finding this thread while searching for information on a problem with my Myryad MCD-500 which has a KSS240a mechanism.
The disc will load and begin to play with no issues, somewhere past the half way point, quite a bit of static starts in the playback. The best way I can describe the sound, is like a radio station that's not tuned properly. If I begin playback at a track past half way point the static starts almost immediately.
I removed, cleaned and lubricated the mechanism based on advice in this very helpful thread, which solved my problem for about 3 discs,
I also noticed the during playback with the cover removed the top clamp appeared to start wobbling slightly as head advanced through playback. By top clamp I mean the disk which is part of the black plastic piece that holds the loading tray in place.
When I saw androa76's post about cracks in the plastic sled, I took a second look at mine and counted 6 hair line cracks from front to back. But, I do not have any skipping or TOC reading problems.
Any suggestions or advice?
Thank you