SONY D-150 strange problem and disc wobble

I recently purchased my second Discman, a SONY D-150 that was sold as untested at a low price.

After receiving the unit, I start disassembling it completely for a good clean and polish.
Right from the start, it was obvious that someone else had opened the unit in the past:
- missing screws, screws different than the original ones, scratches in the battery compartment from trying to remove the battery tray;
- missing traces on the PCB that were repaired with bodge wires (haven't figured out why they were missing in the first place);
- the middle gear, sled motor gear and sled gear were coated with a thick coat of cheap bearing-type grease; however the middle gear was pretty stuck, despite the grease;

After the disassembly, I further disassembled the laser from the unit, sled, sled motor, middle gear and spindle motor, in order to clean everything from that cheap grease and started to re-lubricate the sled and middle gear.
Given the spindle motor was already out, I lubricated its upper and lower bearings with watch oil, for longevity.

After carefully inspecting the PCBs I could not find anything wrong at first glance. All the damaged traces were already repaired (there were only 5-6 repaired traces in total).
Decided to re-assemble the unit and give it a try at this point.

1. FIRST TRY: the unit was sometimes reading and playing a CD, sometimes not. Seemed to work better when help upside down.
I started to suspect a weak laser diode, but decided to investigate further, before drawing any conclusions.

The first thing I tried, since there were traces of soldering paste on the laser head FPC connector, was to resolder the FPC connector and give it a good clean inside with contact cleaner, as well as cleaning the flex cable contacts.

2. SECOND TRY: the unit seemed to work better when held in normal position, however at times it would stop and not read the CD again. It would start working again after some time, indicating an intermittent problem as before.

I decided to give it a test with the lid open and switched pressed at the time when it wasn't reading a disc.

3. FINDING THE REAL CAUSE OF THE PROBLEM
Suprise: the laser was not emitting a beam. This could only have 2 causes: a bad laser diode or a problem in the APC circuit. When measuring the voltage going to the laser diode, discovered it was only 100mV.
Further measurements proved that the LD pin of the RF amplifier chip was too high in voltage, not allowing the PNP side of Q501 to turn on.
The next thing to check was the LDON pin (which has a permanent connection to ground, the laser itself being turned on/off by powering the RF amp itself on/off): after probing with the multimeter (and pressing on the IC pin), the unit started working almost perfectly.
The multimeter indicated a good connection to ground, but it was after applying force through the test probe.
After putting the unit back together and playing a couple of CDs it started acting up again after some time. This time it was clear that a bad connection on the LDON pin was causing the problem, as the laser stopped emitting once again.



4. THE FIX:
In the end, I ended up connecting the LDON pin to the nearest ground point on the PCB with a wire, as resoldering the pin of the IC did not solve the problem.
The GND trace is underneath the chip and it's not worth desoldering that chip, as there is a risk of damagining it from hot air (unfortunately a new one could only be found in a donor unit which uses the same RF amp).
One thing that needs to be mentioned is the IC did not have any signs of previous hand soldering, so I don't think this problem was caused by the previous person, despite the mess that was created.



In the end, I have a perfectly functional D-150, which reads and plays CDs perfectly, including CD-Rs.

 

DISC WOBBLE PROBLEM:

After enjoying the player for a while, I discovered a second problem: the CD had a considerable amount of wobble (about 1.5mm). The servos were able to perfectly compensate this, however it was clear the wobble shouldn't be that high.

The problem was in the spindle itself, as the spring-loaded side in the center required a considerable amount of force to push down and it was clear that the magnetic clamping mechanism did not have enough force to do that.
This would result in the disc sitting on an angle on the spindle, hence the wobble.

After disassemblying the unit again and taking the spindle motor out, I realised that the spindle itself is made up from 2 parts:
- the center metal part that is pressed onto the motor shaft;
- an outer plastic part that is pressed onto the center metal part (but is pressed in the opposite direction);

SOLUTION:

What can happen if one presses a disc too hard when putting it onto the spindle is push the outer plastic part of the spindle down a little bit. Even a tiny amount is enough to cause the sping loaded portion not to work properly, causing wobble.
The solution to this problem is very simple: just pull the spindle until it clicks. Note that there should be a significant gap between the case and the spindle, like I show in the picture.
It is not necessary to disassemble the unit for doing this, just fit a sharp tool like a knife between the spindle and the case and use it to pull the spindle up.
After doing this the wobble in the disc decreased almost an order of magnitude, from 1.5mm-2mm to 0.1-0.2mm.

A little bit of wobble is normal, as the disc itself is not perfect and also the spindle is not perfect (the ones being made of metal are better at this aspect). However, you should not see any visible wobble through the transparent part of the lid.



This spindle problem can appear on any SONY Discman that uses this magnetic clamp mechanism, so it does apply to other models as well (both older and newer).

 

^ good read ^

 

this is a common problem with Toshiba Discmans - for the puck they used a piece of felt gone bad'n'sticky over the ages and pulled out that whole centering ring out! This one here is a standard for most Sony 1st Gen Discmans and so far I've been lucky and never had the 'centering ring' pushed in.


The common problem I see nowadays (but not 5-7 years ago) is a worn-out spindle motor. Mabuchi 410CA used in Sony D-303 and D-66 (and Toshibas) are the most famous - you have to exchange it when Discman plays if held at an angle but skips when lying flat; but even if still sounds OK it is better to exchange it. Thin motor, 1.5mm spindle and probably some design flaws, I have no idea why 410 motors went so bad!... But recently even Mabuchi RF-300 spindle motors (with thicker 2.0 mm shaft, and they are used in most 1st Gen Discmans) have to be replaced to make those old Discmans sound 'like new' again.

A minor miracle - tiny Sanwa motors (1.5mm shaft) that Sony used for D-150 and D-250 spindles, they are still going strong! The thing that worries me - once they gone Bad, there is No substitute!

 

I like to oil the bearings of the motor in the hope this will prolong its life (would do that even on a new motor before installing). I live with the impression that some of the motors used in CD players, walkmans and cassette recorders came with the bearings dry or almost dry from the factory.
I wonder if that's at least part of the reason why so many motors are starting to fail... Another thing all these fails seem to have in common from what you say is the Mabuchi brand...

I've seen that KaosunCD sells replacement motors, which is the good part. At least once these motors fail, there are replacements available.

Regarding the D-150/D-250, the motor itself seems pretty generic, apart from the very long shaft. The spindle itself could be pressed out off the shaft and pressed onto a new motor.
If these fail in the future, that might be the only solution. Of course, that's assuming a motor similar enough and with a long enough shaft could be found.

 

Original Mabuchi RF300, the ones which rattle like crazy, they have a very noticeable 'play' at the back bushing, the one you can not oil. Kaosun suggests drilling a hole there to be able to oil it.
Some RF-410CA and SANWA motors in D-150/250 already have those holes So far I failed to find a substitute for D-150/250 motors, even bought one for $100 from Germany which looked similar. But since the problem is non-existent (so far at least) I decided not to waste any more efforts on it