Sony CDP-3100 Help (pics of insides)

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Hi, I recently purchased a Sony CDP-3100 like this one:


in nonfunctioning condition. The inside looks clean as does the player as a whole. There are two issues I'm observing:

1: the tray opens but doesn't close unless I coax it. The tray open close motor runs the entire time as I do this.

2: I suppose the bigger problem; once closed, the laser doesn't recognize the disk. Without the disk in and the player open I can observe the laser move and everything appears to my eye, to be operating properly. My hope is I can adjust the laser and fix the issue.

Does anyone have any knowledge of these players or Lasers KSS 272A?

I've posted some pics below and have seen other threads on the topic on this forum however I haven't been able to gather any conclusive suggestions.

Laser block and transport:

Dac board:
Some good news; I did a bit of fiddling and the disk now seems to read as it spins for a moment then stops, tries again, stops, then the no disk text appears again. However, the disk now spins to a degree...

What I did: removed the set screw attached to the spindle which raises and lowers the disk platter. I also put one drop of oil in the gap between the spindle and the motor. One thing I'm observing, as the disk spins it seems quite wobbly. This could be the basis for the disk not being able to read. Can anyone suggest how to fix this issue. Also with regards to adjusting the height of the platter, aside from trial and error, can anyone suggest a proper technique here? Thank you. Happy to post more pics while I have the player open.
Joined 2007
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The disc should have no observable wobble when looked at edge on and slowly rotated. If it does then the there is a problem with the platter or the spindle motor (bent shaft)

As to the tray motor running. If the you can stall the tray and still hear the motor run then that sounds like a slipping belt. If holding the tray is able to stall the motor then there could be a problem with the microswitches used to detect tray in/out.
Sonys that clamp the disc by lifting the mech are prone to failure of the lifting mechanism. If the mech doesn't lock home, then it won't play. Most commonly, the disc will be rejected immediately, but in marginal cases it might try to play but not succeed.

The drawer and lifting mechanisms are sometimes related, such that if the drawer struggles, momentum is lost and the lifting mech will likely fail too.

If the lifting mechanism is belt driven, the most likely cause is a stretched or contaminated belt. If gear driven, the correct method of adjusting clearance is generally in the service manual.

If there is a button and sliding sprung boss in the middle of the platter, where the disc sits on the spindle, make sure it's not stuck.
Okay. Thank you for the suggestions. On second look, it seems the disk wasn't, rather it was just an unevenness in the printing of the shiny part of the cd -- sorry I'm not more technical in my terminology in that instance. With regards to the drawer, I believe it is the belt slipping and have ordered a new one. That said, I don't really care whether the drawer works or not (for now) -- will make sure not to bump the little blue switches when gently coaxing it back in.

While I don't know whether it is or isn't a dead laser, I'm more inclined to believe it's not the laser and it's a tracking error of some sort. I don't think the motor is damaged (bent spindle as was suggested) in any way though it may not be spinning at proper speed and need some oil.

Does oiling the motor require removing the mechanism? Not a problem if so however if there's an easy way to do it I'd prefer to go that route.
Manual free here: SONY CDP-3100 CDS-3100 SM Service Manual free download, schematics, eeprom, repair info for electronics

Wait for "Get Manual" to appear below the front-page image and click on that. Clicking anywhere else will get you other stuff you don't want.

There is an exploded view of the mechanism on page 5-4. It is as I guessed...the top clamp is fixed and the rest of the (heavy in this case) mechanism and disc is lifted up to meet it using a cam (part 122).

I see only one motor and belt, so the drawer and lifting cam must be interlinked, such that when the drawer is fully closed, further turning of the motor lifts the mechanism. As I said, if momentum is lost it becomes doubly hard for the motor and belt to lift the mech. If the belt is slipping when closing the drawer, the lifting mechanism will almost certainly fail.

If you assist the drawer to close at its normal speed, there is some chance that the retained momentum will overcome the resistance of the cam, but even this is unlikely.

If the motor has been oiled that could be the cause, because oil is likely to spin out onto the belt. Even a tiny amount on the belt will cause it to slip.

If a new belt doesn't fix it, then a thorough clean and very careful and sparing lubrication of the cam and other sliding parts of the mechanism may help...some old Sonys used a grease that eventually turns to glue. Again, be careful not to contaminate the belt or pulleys.

You must use fully synthetic lubricants, because mineral oils and greases attack many plastics. The best are intended specifically for plastic and can be found if you search for "plastic grease". Silicone grease is not as good a lubricant but is generally adequate and more generally available.
PlasticIsGood has given good advice.
This general type of mechanism is used in most of Sony ES CDPs.
There are 3 things to check:

1) Tray motor pulley and belt - must not slip and the belt must be tight. This motor also operates the cam mechanism that lifts the mechanism and CD to mate properly with the clamp which is in the top fixed clamp holder. For debugging purposes you can remove the holder (4 screws) and also take the clamp out by rotating one of the rpund metal rings holding it inside the holder, then use the clamp itself to clamp the disc manually, WHILE THE TRAY IS CLOSED and the mechanism fully lifted. The cam can usually be operated by a small screwdriver from below, through a hole in the bottom cover, this is normally used to open the tray when there is no power available or it gets stick with a disc inside. Also check that the cam and associated cogwheel mate properly with the tray (look at the tray from below, there is a toothed cam along one edge which terminates in a semi-circular extension, when the mechanism gets to that point on the tray, the cam operation takes over to lift the laser assembly and disc upwards to mate with the clamp).

2) Microswitches that detect tray position. There are two, one detects tray open, the other laser assembly locked into the clamp, this also implies tray closed if all of it operates properly. If the electronics does not detect the correct state of the switches, it will attempt to eject the disc. However if no switches operate, it will cycle continually between tray in and tray out, the motor will be spinning all the time.
Some versions of this mechanism with the control electronics fotted to the mechanism itself have a common problem, the position switch signals get cut off on the way to the electronics. The reason is corrocion, caused by a memory retaining capacitur (supercap) leaking onto the PCB and corroding tracks or, most likely, vias that connect the top and bottom layer tracks. Usually the culprit is a via that supplies GND to the switches.

3. Position of the platter. This is described in the service manual, but you can also find it in all manuals for CDPs that use the same mech (CDP-X 339, 303, 559, 505, 779, 707 and there are others). There are two hex set screws to adjust this, the manual gives the correct position. After it has been checked and set properly if necessary, it's best to check operation with the clamp taken out of the holder, and the holder dismounted, and cam manually operated to put the mechanism in the correct position, also checking that position switches work properly. This eliminates possible problems with the cam, relative position of the tray, loading motor and similar ptoblems, so you can get a good idea if the laser works. In some cases unfortunately the laser hed can have mechanical damage and appear to work better when the position of the platter is changed. This happens when the plastic gimbal holding the lens fails, usually because the plastic goes brittle, and this in turn usually happens for heat and chemical reasons, most notably as a result of cigarette tar. The yelowish color of the gimbal and any metal parts that should be silvery is a clue. Unfortunately, there is no other fix but to change the laser, and in this case you will be better off finding a lesser working unit as a donor.

This laser head has glass lenses, which also makes it possible to clean them well, including the internal lens. Not for the faint hearted but it often means going from an apparently dead laser to a fully functional unit.

Regarding odd behavior in CDPs using this mechanism, speciffically CDP-X779 and 707, some units have a factory bug. The linear motor and laser focus coil drivers use a low voltage negative supply for compatibility with 0-5V input PWM signals. This is normally done with a simple linear regulator with a 3.6 or 4.3V zener. The error is a far too large resistor supplying current to the zener resulting in lower and unstable voltage aross it, which often drops to zero when the servo system is taxed more, such as marginal discs. This results in temporary latch-up of the coil driver amps and loss of servo action, and in turn this resets the servo chip, resulting in periodic audible dropouts similar to what one gets when a disc is heavily scratched. In bad cases it can block the whole CDP in an error condition (display says 00 and eject does not work until it's reset by cycling power), in some cases eject will work but wil eject the disc while still spinning (often very fast). This can seem like a bad laser but in fact the clue is that the dropouts do not occur in sync with disc revolutions. If so, check that negative supply. One fortunate part is that one can often find cheap parts units with a supposedly failed laser that actually have a good laser but bad regulator.
Your post #2 points out towards an unfocused laser probably due to lens support ageing.

Gajanan Phadte
How do you know?
Do you know where a replacement KSS272a laser head can be found? Last I saw, a complete mech went for 350 euros, second hand.

Edit: Sure way of testing whether lens support is a problem.
Put the player upside down and play. If it plays, then it is the lens support problem.
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There is one out of the box way of testing the lazer, but one should be daring enough and careful.

Let us consider one situation where the platter is lowered.
One of the two things that change here is the distance. This leads to more reflection(intensity) from the cd. This more intensity is good enough for the photosensor sensor to detect the presence of cd which in turn makes the cd to spin, for further reading process.

The far out solution...
On a discarded or a blank cd, paste a good reflective foil/sheet on the data side of the cd. This pasting should be good enough and uniform to prevent sheet coming off.

If your player was not initiating the spin motor due to the weak lazer, this cd will increase the reflected intesity and will spin the cd.

However, totally dead lazer will not show any difference and can be checked visibally.

Gajanan Phadte
A belt is never involved in the spinning and playing process of a CD player and is mostly used in tray movements.

I can advice on using an oscilloscope, but is it within a DIY repairers reach, who just wants to fix his CDP and feels that the replacement part is too costly.

This is a one off solution for easy way of testing a laser.

Gajanan Phadte
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