Laserology

Some thoughts about laser failures that never happened.

And about those that did.

Hey, do you know where I can buy a new laser for my CD? It just died.

I heard it so many times that I decided to write about lasers, their problems and easy fixes.

I looked inside over 100 CD players which DID NOT READ the CD anymore and only one (in decimal and binary mode it is 1) had failed laser. And that one was dead because of my stupidity. But it (my stupidity) is not the subject of this article.
Other peoples stupidity is.

Anyway, what happens is that there is probably 20 different reasons why the CD player does not read the disc, and people have such strong prejudice that they all call these failures DEFECT LASER.

This is CRIMINAL because lasers are not produced anymore, and the scarce resources left, the holy reserves - are brutally cannibalized by people who know no better and simply buy the new units.

The top ten reasons why CD's are not read - according to "my vast experience" in that matter - are:

1. There is a CD disk inside the player as resulting from moving to a different house with the disc left in the drawer. Disc falls out into the guts of the CD player and blocks the mechanism. When the owner puts second disk afterwards - the player rightly displays ERROR.
- remedy: the first cure that springs to my mind is - open the CD and remove the stuck CD.

2. The 20 year old belt that powers the drawer starts slipping or breaks. After closing the drawer - CD is not properly positioned on the spindle.
- remedy: replace the belt

3. The CD player was being used in a dusty environment and the dust or cigarette tar settled on the laser optics. Dust causes beam dispersion. Laser looses focus.
- remedy: open the player and clean the laser surface with a Qtip. First- with wet tip dipped in the window cleaning liquid, then - dry one.
If this is not enough - clean the laser INSIDE the reading head. This is for advanced people. Better to give this job to a watch repair man. See below - some pics.

4. The power supply of the laser circuit is defective: either too low voltage, or noisy, or starts oscillating from poor filtering or regulation. The cause may be dried out electrolytes.
- remedy: replace all electrolytes in the digital part of PCB, or better - all of them.

5. There is a cold joint in the laser circuit.
- truth is that the solder joints do corrode and do fail. Our best players are 20 years old and this shows. A joint which is hot, like a leg of a regulator, or a point where the raw supply is rectified, or a laser power controller - from the heat they develop accelerated deterioration - mixture of oxidation, flux burning, and tin evaporation.
- remedy - look at all solder joints, especially around laser cable connectors, around all regulators, around places that look toasted, brownish or cooked - and re-solder these points adding a bit of fresh solder with fresh flux.

6. Moving cables - or ribbons - do get broken after a million bends.
Check for continuity in flexing ribbons leading to the laser, the drawer, the motor or the tracking mechanics.

7. The tracking mechanism accumulates dirt, hairs or dust on the greasy part and the tracking can not arrive at the center-most starting position. With every ride of the tracking - the dirt is pushed away and forms a sort of a "bumper" that stays on each side of the shaft.
- remedy: clean the tracking shafts, axis and rods at their extreme ends.

8. The main motor is not keeping the right speed.
- it will look like the laser can't read, but it is simply the wrong rotation speed. May be caused by CD slipping on the spindle, or motor defect, or something blocking the CD like audible friction against the surface of the drawer. For instance - the spindle can wear off its bottom bearing and the whole CD will be lower by 1/10th of mm. The laser will loose focus and the top clamp will not press hard enough. In any event - the spindle must be brought back up this 1/10th of mm.
- remedy - if the motor is just a normal Mabuchi for 5 bucks - replace it. If it is a CDM or KSS Magnetic series with brushless motors - just adjust the spindle height.

9. There is a hair or something else inside laser focusing mechanism
The laser can't freely move up and down. Since CD is strongly electrostatic - it attracts hair, dust and animal furs. During playback - these can get caught under laser focusing suspension.
- remedy - remove the obstacle.

10. The CD does not spin.
After closing the drawer nothing happens and defect is displayed. It maybe just the result of not spinning at all. The CD behaviour must be observed - so the top cover must be removed.

CD laser diagnostics - a quick guide

Is CD laser really dead ?

Without specialized equipment we small mortals can diagnose the problem pretty well and save tons of money on service.
Or even new laser purchase. Or even a new player.

1. Open the player's hood

2. Put the original factory made CD with clean surface and press drawer CLOSE button.

3. Does the drawer close fully?

4. If 3 is yes, then does the CD spin at all?

5. If 4 is yes, does it spin for 2-3 seconds or for over 10 seconds? Does it spin VERY FAST like crazy or with somewhat controlled speed ?

6. If the 5 answer is - controlled speed and 2-3 seconds - the laser is alive and it can detect the beam reflection from silver surface.

Tips: if the laser is dead, the CD will not spin at all. The CD motor has a signal to start spinning only after the laser heads reports: "reflective surface detected on the height where CD is expected to be ". However, as someone rightly pointed out, some servo mechanisms will try spinning without checking if CD is in place or not. Apparently, they made assumption that a small motor spin in vain will not hurt.

7. Does the display show after 3 s of spinning the correct number of tracks and time ?
If the CD was spinning but can not show time - it means it could not read the TOC - famous Table Of Contents. So the laser head was seeing the disc surface but could not read the first line of data. This first line is at the very center of CD disc, so the tracking of the laser assembly must be on position "center most". The inner-most position. So if we have a tracking problem - we cant move to the very center and TOC cant be read.

8. If the TOC is displayed correctly but the PLAY does not happen - it means that:
- laser is OK
- TRACKING does not move the laser from first "groove" of the disc to another. Then go down to tracking problem chapter.

9. The CD starts to play, but skips
- observe if it skips forward or backward. If there is a mechanical problem - the advance of tracking is blocked - the skipping will happen backward. If the tracking controller is too enthusiastic - it will skip forward.
Adjust the physical levelling of the CD player, and adjust the tracking gain (see below).

10. The CD plays well the factory CD's but fails on the CD-R's
The laser focus on CD-R is different than in factory CD. The pit reflection is also different on these two CD media
The amount of plastic film that protects the metallic layer in the CD and CD-R is very different.
Generally, it is always easier to read the CD than the CD-R, no matter how good is the blank media and how slowly it has been recorded. Not to mention the no name CD-R recorded at 24x.
So if the normal CD plays well and the CD-R plays faulty (distorts, skips a lot, reads slowly or not at all) there is probably a problem on the horizon. The system is already too weak for CD-R but still somehow manages on regular CD's.
This common problem can be a result of any other problem listed above - dirty laser, bad adjustment, worn out spindle, slipping disc, slipping belt, anything really. INCLUDING of course - a dying laser. All slowly building-up problems show on CD-R's first, months before CD's will show same problem.

Problems 9 and 10 usually get worse as the laser is further away from the center - meaning - on higher number of the tracks. If it starts skipping on track 4, it will probably very badly skip on track 10th and never ever reach track 12th.

11. Lasers which die on players bought 2 weeks ago from E-Bay
If the otherwise excellent, pretty and valuable mint player starts having laser problems at the original owner, it will inevitably end up in the hands of the laser guru, who will turn up the power of laser emission. It may help the laser to read better TEMPORARILY.
Then the guru gives the player back to the owner and says: " well, I managed to help you, the bill is 200 Euro, but take my good expert advice and start looking for a new player. This one will not last long. Sell it quickly, while it still works okay.
Then the owner goes home, and he freaks out. Gee, if the adjustment costed me 200 Eu, how much is gonna be next time around, when the big un strikes ? So he puts it on ebay with a story attached about the uncle who passed away and while the nephew was cleaning up his house this cd player was found. (Funny that these houses always get cleaned by the nephews not sons or wifes) It was always well taken care of because the uncle was a music lover. He only listened to it occasionally - one opera CD every sunday after a mess. It is sold as it is, without warranty, because the young nephew is too busy to check it. "
That is how mint collectors players end up in the hands of happy new owners only to die 2 weeks later.
If that story is familiar to you - the laser is REALLY DEAD. A dying laser with cranked up emission will die very fast.

Example of Sony KSS151A laser deep cleaning procedure

The laser protection cover must be first removed (Example of Sony KSS151A, similar to all other Sonys.)

The upper lens can be gently lifted up by 1 cm or so.. Be GENTLE.

laser cleaning

My Q-tip cleans the lower lens. But please use NEW q-tips, without ear wax on them.

Cleaning CDM1MkII, CDM2, CDM4 fro Philips

The upper lens can be safely removed by unscrewing the screw that holds it.
Underneath we find second lens - this one non-removable. We can clean it.

We can also gain access to clean underside of the upper lens.

True indication of a dead laser circuit (not necessarily the laser itself)

If you observe the whole CD starting procedure with player's hood removed - and after properly loading the CD in the position - the CD does not spin at all - there is high probability the laser is dead.
Turn off the light and repeat the drawer closing process WITHOUT any CD. Look at laser: does it emit red beam - does a VERY tiny dot inside the player lens blink? It is activated only during the first 2-3 s after drawer closes, and always during the lens focus movement up and down.
(of course do not look too closely or straight - just a glimpse from the angle is enough)
If there is no red dot - no laser emission. But maybe it is the circuit ?

Another thing to check - providing the red dot is present - does the lens move up up and down repeatedly 2-3-4 times? It is a process where the laser tries to catch focus on the reflection from CD. If the red dot is there but no focus movement - the focus circuit is dead. Still - no need to replace laser. Check it with no CD - just open and close the drawer to initiate the focus movement procedure.

If the laser moves focus lens up and down and it finds reflection - the motor of the main spindle will get the instruction to turn clockwise.

If the laser beam works - chances are high - the player can be repaired to serve you again.

Electrical circuits of the CD reading process:

There are four circuits that are responsible for the whole process. Each one has adjustments and it has own dedicated power control chip. The power control chips often fail in Sony machines. They can be specialized chips, opamps or transistor pairs.
The power control chips in turn are managed and controlled by servo processor which gives all commands and checks if all is OK , it is called the logic. It also decides about problem management: should I keep trying, and when to give up.

Circuit No. 1. Laser focus - controls electromagnetic motor suspending the laser lens on the right height.

Circuit No. 2: Laser power - controls the emission.

No. 3 is tracking gain - which controls where the rails should be relative to the CD tracks.
To check the circuit - open the player, without any disc - move gently with your finger the laser assembly to off-center position while player's power is OFF.
Turn the power ON and see if the tracking will bring the laser assembly to the center-most position. If not - the tracking is fucked up.

No. 4 is the reading circuit - the laser beam is being read by the photo diodes and the data stream is being formed.

Needless to say - there is also the motor speed control circuit.

On the more highend machines like KSS151A, KSS152, KSS190, BU1, and other large and heavy HAAL motor magnetic rails - the power to move the mechanism (tracking) is relatively very very high. Much higher than on the mechanisms like modern DVDs, PC readers and play stations where the tracking is done by a motor with snail gearbox. The circuits that send huge current to the electromagnets are very big, their transistors and chips get hot, easily fail, and also burn out solder under their own solder joints.
These machines were gorgeous when new, but after 20 years may fail.

CD laser transplants

Well, I am not a big fan of laser transplants. Unless you have IDENTICAL laser - it may be difficult. This is doable for very advanced technicians. I am not experienced in this department.

CDM0 and CDM1 are probably possible to cross transplant. A donor in good shape is hard to find though.
These two are probably the best lasers and best mechanisms ever made. Especially their lasers which belong in military rocket science - real multi lens glass type ones.

The CDM1 MK2 is in fact not a newer MK1 but it is a CDM4 in pro version. (meaning - with metal cast sub chassis) The transplants from CDM4 to CDM1mk2 are supposedly successful and worth the hassle.
Donations the other way around would be stupid.
The CDM4 is very popular and easy to find, but there is - I counted - over 5 variants that do not cross breed easily.
The most popular ones are CDM4/11, CDM4/19, CDM4/21, CDM4/25 and CDM4/44 if memory serves me.
CDM2 is a bad mechanism that fails a lot and is probably compatible with CDM1 MK2 and some CDM4 's but don't take my word for it.

CDM9 is alone, no twin brothers, sorry, but it almost never fails. I love it.
CDM12,x and VAL12,xx and VAM12,xx are available on the market as new for 20 Euros or so, so don't bother to seek laser donors.
CD PRO from Philips is so rare that I have no first hand experience. It probably is as good as it gets.
Sony cheap ones like KSS213, Kss 240 and so on - exist in plenitude on after market.

WARNING: a man of knowledge told me that there are NO GENUINE spare NOS lasers or mechanisms on the market today - all of them are either factory rejects or copies. It does not mean they are bad - not at all, but they nevertheless are NOT GENUINE. This applies to both Sony and Philips units. Chinese factories make tons of lookalikes.

Links to sites about CD lasers and mechanisms:

When looking for a laser transplant - the first place to visit is Vassili list of players to see the possibilities of donorship.

http://www.vasiltech.nm.ru/files/cd-players/CD-Player-DAC-Transport.htm - list of DAC and transport

There is also this cool laser list - incomplete but at the same time - very detailed for some manufacturers:

LASER LIST FROM JAPAN

There is also a must read web site from Netherlands at the Vintage knob service.

interesting read about CD history:
http://news.bbc.co.uk/2/hi/technology/6950933.stm

About the RED BOOK
http://www.nationmaster.com/encyclopedia/Red-Book-(audio-CD-standard)

WIKI
http://en.wikipedia.org/wiki/Compact_Disc

http://www.answers.com/topic/compact-disc-player

Adjusting the CD mechanism adjustment pots

Oooouuugh this is a tough subject.
If I advice you to turn these pots, I will end up being forced to answer 10 000 emails begging for help.
My advice is NOT TO turn the famous pots which adjust the laser, focus, tracking etc. But you will do it anyway, I can't help it.
All I can say, that after fixing 100 player lasers - I know how to do it and THAT'S WHY I know I should beg you not to try it at home.

However, if you have a dead player, and you read all the above article, and you think you have nothing to loose - try turning the pots.
FIRST MARK THEM WITH MARKER PEN TO BE ABLE TO RETURN PRECISELY TO THE STARTING POSITION. Your wife's nail lacquer is a good alternative but leave it to dry.

After marking, read the descriptors on the PCB silk-screen:
Philips uses 2 pots - one for focus one for tracking.
Without manual you can identify them because when you observe the laser lens while turning the focus pot - the lens will also move up and down.
The Philips pots are adjustable with hex allen key
Philips machines like CDM are usually easier to adjust than Sony breed - with their 4, 5 or even 6 pots. But in Philips machines these pots are usually hidden below the transport. That's too bad. Sony allows us to turn easily while playing.

Sony Machines have descriptors marking the pots: FG (focus gain) FB (focus bias or balance) TG - tracking gain and TB - Tracking balance.
There is also absolute power adjustment and one more which I cant remember.
If you don't mark the starting positions with pen - finding the G spot again will be as possible as winning the lotto. Don't even try it.

Only turn the pot responsible for your problem: focus for focus, tracking for tracking etc.

In 90 % of cases the pots are OK in the center position. If the pot must go (or it is already) in extreme position - it is an indicator of big trouble.

pots

note the blue pots are for focus, white for tracking, and the copper radiator is for power control chip. The micro CXA1081 provides the servo logic. Actual photo from Sony 227ESD player which has magnetic rails tracking and KSS151A laser.

WARNING: Each time you move any pot - the drawer must open and close to reset the setting memory of the servo.

So any change of pot must be followed by the drawer opening cycle.

There is also a technique of finding the pot position by ear - mis- adjusted mechanism make noises like constant focus-finding noise or tracking skip noise. You can HEAR the laser being unhappy. If all is OK - the laser system should be silent and quiet at playback. Listen carefully to the laser while turning the pot.

Having said all that - avoid opening the Pandora's box of pot turning process at any cost.
If you are so stupid to ignore my warnings - it is THEN when you will really fry the laser and you can really report it dead. Dead DEAD.