WEIRD problem with CD player

That type of motor normally has many connections to the stator coils, which are a comparitively heavy assembly in themselves. I would suggest that the first move would be to resolder all of those connections, if you can even get at them.

Arfa

I agree with Arfa, sounds like loose solder somewhere on the wires or on the pcb. Sony also had problems with ribbon cables.

Sparkey

Its more likely the laser focussing circuit is off somehow, and only actually locks onto the disc with the mechanical lean to one side. A gentle!! adjustment of laser power, Fgain and Foffset (remembering their original places) may help.

If however there are squeeking noises from the laser while the disc doesn't spin then its possible you have a spindle drive problem.

Sorry Cliff, but having worked on Sony CD players since they first came out, I would absolutely dispute that your scenario is " more likely ". Focus servos will lock a normal focus motor ( and indeed likewise the tracking servo will do the same for the tracking motor ) at ANY angle, including upside down. The lens, lens suspension and tracking and focus motors, do not have enough mass to be sufficiently affected by gravity, that any such effect is not easily compensated for by the power of these motors. I can't remember *ever* having had a situation where focus gain and offset adjustments have drifted on their own to any degree anyway, and still less, have caused a problem that could be corrected by imposing a mechanical tilt to a deck.

Also, I would absolutely advise against adjusting the laser power - not even gently. It is NOT a valid adjustment on any Sony player, and in fact, on very few players of any other manufacture, Pioneer being a notable exception. Indiscriminate adjustment of laser power - even by a *tiny* amount, can readily result in destruction of an otherwise good laser. Focus gain and focus offset should only be adjusted with the benefit of a service manual, and the proper equipment, or by long experience.

The comment about being able to hear the servos squealing, if you rock or rotate the disc by hand when it's not turning under it's own steam however, is a good pointer. If you do hear the squeal, there's a good chance that the focus and tracking servos are locked, and the spindle motor is just not being driven. If there is no servo squeal, then probably, the servos are not locked, which is causing the system control to inhibit the spindle servo. I would still be looking at the spindle motor stator connection soldering first, and also at any connectors and wires going to the spindle motor board.

Arfa

Hi!

even

Okay...not that I disagree or anything like that, but why is this adjustment provided if you're not supposed to use it when servicing the player? Why spend the money to include such a thing? Is it for "factory setup only"?

William

Lots of adjustments are critical in various electronics. What about high voltage regulation adustments in CRT based sets. Would you just randomly tweak it up if the pix was weak? Most LP adjustments are not going to do much beyond shortening the life of the pickup.

Leonard

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Hi!

You'd get no argument from me. I know the critical nature of adjustments in electronic devices, and even understand why some of them are not made to be adjusted. But that's not really answering what I asked. I suppose it is possible that I'm asking a question that only CD player manufacturers could answer. :-)

I'm not wanting to come across as impolite. I'd simply like to know why this is done.

William

Your question is not impolite, and I'm sure would not be taken as such by anyone on here. Asking is how you find out.

The manufacturing tolerances of the optical block itself, are subject to an amount of spread. These are compensated for when the block is manufactured, by putting it into a test jig that sets certain conditions that should result in a certain range of drive currents to produce a specific level of laser diode output. The pot which sets the drive current is adjusted to achieve what the manufacturers consider to be ideal for that particular laser diode in that particular model of optical block. Once this setting has been made, the pot is very firmly sealed, not just to make it vibration proof, but to indicate that it should not be adjusted from its set position. This is the case for almost all optical blocks. Other characteristics that may result from mechanical tolerances of the deck that the optical block becomes fitted to, or tolerances in the circuitry that the block has to work with, are often provided with adjustments which are intended to be moved as part of a servicing procedure.

Examples of these are focus offset, where the zero point of the servo is set to match the average mechanical zero focus point, which should of course be the mechanical resting point of the lens suspension, but may not be if the turntable height is not set exactly correctly. Likewise, tracking offset does the same to compensate for mechanical errors in the tangential or tilt directions. There may also be adjustments which set the gains of the servos to take into account spreads in the servo circuitry. However, many players from the last 10 years or so, have no service physical adjustments at all. With these players the chipsets used have fully electronic internal adjustment systems.

As I said in the previous post, one notable exception to the "don't touch it !" rule, is Pioneer players. The laser power pot is a minuscule little thing located on the laser flexiprint, and is adjusted as part of the setup procedure. Pioneer provide a set of testpoints in a single row on their players, and detailed instructions in their manuals, on how to adjust the entire pot-set, which is often a total of eight pots, and which includes the power pot. Interestingly, Pioneer lasers very seldom fail or wear out. I think in 30 odd years, I have only ever replaced perhaps two of the original types ( there were several, but all pretty similar looking ) and maybe two or three of the later ones which have a couple of tiny pots on their PCB.

Arfa

This is an interesting point about the Pioneer pickups. Ican't recall ever changing more than one or two myself. I worked at a store that sold tons of Pioneer (Elite, mostly) and since then have not workde on them very much. I can recall cleaning lots of spindle motors, but rarely, if ever changing pickups, Is this the experience of others? What would you attribute the difference in reliability to? Pioneer has always had very good laser products in terms of performance. Do others percieve the reliability to have been very good relative to their competitors as I do? Are the current and lower end products holding up as well?

Leonard

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I have run thru the solders on the drive board and elsewhere. The drive is fine when it runs and the "tilt" is a specific angle and repeatable with bumping and jarring having no effect.

I am suspecting that it has something to do with the laser itself since the fix (tilt) is so repeatable. It is definitely on the deck. I checked out all the switches and the board on the deck removing and replacing all connectors.

Apparently the electronics need feedback from the laser to tell it there is a CD in the deck before it will generate the drive for the spindle. >> Is this correct???

Therefore the Laser needs to see a reflection. So if the laser is tipped, the reflection won't hit the right spot on the assy. I see only a movement, apparently controlled by coils, that adjusted the laser along the radius of the CD.

When it does play, I see the sled shaking back and forth as if following the CD. Shouldn't the laser itself be moving by the coils mentioned above. I think this deck has three lasers to control tracking. I have no idea how this works. I only see one lens.

thanks for the responses.

The laser power is set at the factory. Only a few components determine the laser power and they don't really change much with age or use. The feedback circuit maintains the laser power constant should the output from the laser diode itself with respect to current descrease. One thing that can affect it though is that dust, dirt, contamination on the optics between the laser and the disc and photodiode can result in less optical power reaching the disc and/or being reflected from the disc to the photodiode. In this case, if the optics can't be cleaned - which is likely for some of it - turning up the laser power is the only real option. But it's a last resort, not a first resort! As has been stated, that's a good way to kill a perfectly good laser.

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See the CD Player Repair guide at the site below.

The sled should not be shaking back and forth, only the lens. The sled should just move occasionally to maintain the lens centered withint its range.

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One reason Pioneer pickups were so reliable is that the pickup was mounted "upside down" on many models, thus very little dust etc would settle in on the turning mirror. Still, even their models which played the disc label-up were very reliable so far as pickups were concerned. Except of course for those which had the lens fall off...

Mark Z.

SAM Excellent info! Thanks -

This assy appears to have the Laser and photodiode array swapped position wise - IE array is at rt angle to the lens.

But that doesn't tell me why I can start the CD in a tilted position then lay it flat and it will play just fine till I stop it and try to restart it. It will only START in the tilted position, but will continue to play in any position. It also must be tilted on power up or insertion to read the TOC, otherwise it won't start on "PLAY" at all. I just can't picture anything inside the laser assy that could be that free to move and also be controlled to lock it into position so that it would continue to play once started. The lens assy only rotates on the plane of the CD and doesnt appear to have movement in the "tip" position.

DOES the array need to see anything to cause it to start? DOES it search at all by adjusting the tracking of the lens or the array to FIND the CD? DOES the array adjust ITSELF to provide tracking? If so how?

thanks

Hi Mark

Have you ever managed to replace a completely missing lens, with one from a different pickup ? I had quite an argument with someone once, who said that it just can't be done, but I do it all the time - I should think at least 4 or 5 a year - did one just 2 weeks ago. I use a lens from a scrap KSS series pickup. I think that the trick to getting it to work - or indeed even replacing the 'real' lens when it's still rolling around in the bottom, is to make sure that //every last trace// of glue is removed from both the lens suspension, and the underside of the lens lip, and then to make certain that the lens is refitted absolutely flat. I then refix it, by putting a couple of tiny drops of cyanoacrylate superglue onto the tip of a tiny flat-end jeweller's screwdy, and letting it seep into the crack by capilliary action. Sometimes, I've found that the focus bias and offset need to be adjusted slightly to optimise the performance back to normal, but mostly, I've found that it just works right off, with no improvement to be gained by adjustment. I'd be interested to know what others' experiences of dealing with this problem are.

Arfa

"Sam Goldwasser" wrote in message news: snipped-for-privacy@minus.seas.upenn.edu...

I agree with Sam. As to whether the player needs to see a disc on the turntable to spin it up, this depends on the unit. Some players will just go ahead and turn on the laser, and spin up the disc, as soon as a 'laser home' signal is detected. Some coarse speed adjustments then take place, along with focus seek, until the spindle servo starts to see valid data coming off the disc, whereupon, it will lock, and the rotational speed will stabilize to the correct value. Other players will switch on the laser as soon as the home signal is detected, and go ahead and look for a reflection from a disc. Coarse focus search will take place at the same time, until the focus servo locks. At this point, the drive to the spindle motor will be switched on, and the data search will commence. Some players, if they fail to detect an initial reflection, will pulse the spindle motor to rotate the disc some, in case there was a jammy fingermark right above the lens, so there is no simple answer to your question regarding the point at which the disc should start to spin.

Whether or not the deck is on the tilt, the outgoing and returning beams, should not hit any different place on the disc, or the pickup photodiode array. This is the whole purpose of the tracking and focus servos. The lens suspension is very soft, and the mass of the suspension and lens is very small. The focus and tracking motors, which are actually like tiny loudspeakers acting on the lens suspension in all directions, are plenty pwerful enough to hold the lens in the right place, irrespective of gravity acting on the pickup in any direction.

When the disc is rotating, you should be able to see the lens moving up and down a little, as it follows the irregularities in the flatness of the disc ( don't believe the specs about disc flatness and eccentricity ... ) You may also be able to see *slight* side to side movement of the lens if the disc is particularly eccentric. To see these movements, you will need to be on the last track of the disc so that the lens is at the disc edge. These are the only movements that you should see with the disc playing normally. The laser is moved on by another motor via a gear reduction system. Approximately once every four to six seconds, you should see the whole laser head move on by about one tooth. This movement should be smooth and regular, and there should not be any overshoot. You certainly should not see any shaking or violent movements of the lens, or pickup, in normal play. If the problem is within the laser, then I think that it would have to be something like a loose critical-angle mirror, that only lays in the right place with the laser tipped, in which case, the only solution would be a replacement laser. What laser type is fitted, as a matter of interest ? Many Sony lasers are really quite cheap. Also, I take it that the disc is clamping correctly to the turntable ?

Regarding your question about the three lasers. It does not have three lasers as such. It is a single laser diode, whose output passes through a splitter, to create three beams. The middle one of these is the one which should be centred on the disc's spiral data track. This is accomplished by keeping the two side beams an even distance either side of the track. To do this, these two beams are focused onto two diodes in the pickup array. They are called the "E" diode and "F" diode - hence the servo adjustment "E-F balance". When the middle beam is exactly on the disc track, and the E-F balance adjustment is set correctly, the outputs from the E and F diodes will be equal, and there will be a null servo condition. As soon as the beam moves off track, the E-F output will become unbalanced, and a positive or negative servo condition will be created to correct the beam path. Focus servo operation is likewise based on signal imbalance, but this time as a result of the central beam being focused onto the "A", "B", "C" and "D" diodes. When the beam is correctly in focus, it will be circular, and all four diodes will be equally illuminated. If the beam is out of focus, an astigmatic condition will be created, illuminating two of the diodes by a greater degree, creating an inbalance, which drives the focus servo in the appropriate direction to restore correct focus. Which two diodes are illuminated more, depends on which direction the beam is out of focus. Data output is the result of adding the outputs from these four diodes.

Not all optical blocks are 3 beam. Some are single, and use a completely different scheme for deriving the servo information.

Arfa

I don't know if I will ever get this working right, but I sure am learning a lot.

I'm sure this has to be looking for a reflection before it decides to starts up the spindle.

I can't see the lens with the CD in. If I put a clear protective disc in, nothing happens because it sees no reflection.

The unit is a CDP-302, a high end unit. The tag on the laser assy is BU-1

119712

And from its construction, to replace it might cost the same as what I paid for the unit new.

Since it will play in any position once started, is it possible the focus/tracking drive isn't working till it starts and the at rest position is causing the reflection to totally miss the target.

I re-attached a lens just the other day, but have never tried using one from another brand pickup. If I don't find the original rolling around in there, I just consider it a lost cause.

BTW I have found that Pioneer lasers which oscillate have the lens coming loose but hasn't fallen off yet.

I don't use superglue because of the danger of it fogging the lens.

Mark Z.

Point taken on the lens fogging. It actually happened to me on one of the first that I tried to reattach some years ago. That is why I now only use the tiniest drop, and let it draw itself into the gap. Fuming and fogging is then not a problem. Next time you get a missing lens, just give a Sony one a try. If it's a lost cause already, you've got nothing further to lose !

Arfa