OK, Here Is A LONG Shot, But....

You're right, long shot. Very long shot.

Why bother fixing it?

I got it for free; it seems like a (fairly) nice CD player; just curious about the sound.

I really don't know if I actually need the schematic. I'm pretty sure it's a bad op-amp. The CD spindle motor won't activate, even though the motor tests fine and so do the transistors responsible for supplying the motor voltage.

It's just something to tinker with on a rainy afternoon, that's all......

I got it for free; it seems like a (fairly) nice CD player; just curious about the sound.

I really don't know if I actually need the schematic. I'm pretty sure it's a bad op-amp. The CD spindle motor won't activate, even though the motor tests fine and so do the transistors responsible for supplying the motor voltage.

It's just something to tinker with on a rainy afternoon, that's all......

The fault you describe really is a bit "my car won't start even though there's fuel in the tank. The engine cranks so the battery is fine. I suspect it might be a bad radiator ... "

Sorry to put it that way, but very few problems with discs failing to spin up, are ever anything to do with the motor's drive electronics, *unless* the motor was faulty in the first place, in which case, occasionally, the motor driver IC, where one is used, will be damaged. Where the drive is from a four transistor bridge, it's very rare for them to have failed, bad motor or not. The disc failing to spin up, when it's definitely *not* a motor problem, is almost invariably because the system control is not releasing the motor servo into a 'run' condition.

First checks should be :- If you move the laser down its track manually, then open and close the drawer, does it then home ? Does the laser burn ? Does it attempt focus ? With a disc in, does it achieve focus ? Does it attempt to rotate the disc at all ? Are any pots in it way off centre (if you don't know its pedigree, the phantom pot-twiddler may have been in there before you ... ) d;~}

Collect a bit more info, then let us know, and we'll see if we can suggest some more things you can look for.

Arfa

Arfa:

Thanks for the helpful information.

All I know at this stage is that the CD will not spin under any condition...HOWEVER, when you turn the power off, the CD will spin maybe a quarter of a turn while the unit is powering down.

And here's a strange fact: The other day I started messing with the player after having it sit for a couple of weeks. I switched it on and inserted a disc. Quite unexpectedly, it spun the disc and the disc's track information appeared in the digital readout window!

At that point I should have pressed "play" to see what would happen, but I ejected the disc and re-inserted it. Back to square one--the disc didn't move.

This has been the one and only time the player has ever spun a disc since I acquired it.

I have measured the voltage coming off of the four-transistor bridge. Whenever a disc is inserted, the necessary 5 volts appears for a MICRO- second, and then the voltage goes back to zero.

Respectfully, you emailed me first about this player. I assumed you had actualy looked in the CD repair FAQ. Apparently, that wasn't the case. Instead of taking up everyone's time answering basic questions, please go to the "startup problems" sections there and attempt to determine exactly what it is or is not doing. Then, everyone can be of more help.

As has been noted by others, the spindle motor failing to spin is almost never a problem with the motor or its immediate driving electronics, but rather with the optical pickup not getting focus lock due to any number of causes. With your erratic behavior it could even be a something mundane like a bad flex cable. And, it could still be a dirty lens.

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ase.

Hi, Sam:

I really apologize, but I don't think I e-mailed you about this player. Unless I am having a severe case of amnesia, my original post here is the first time I have discussed this player online. I did have a question about a Yamaha player a couple of months ago, but that issue has been resolved.

If I did indeed e-mail you about this player, please accept my apologies. I will consult the CD repair FAQ as you have directed.

My apologies. It was someone else. Probably the "long shot" part made me think it was you. :)

Anyhow, do read the CD repair FAQ and then you can post your findings.

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I have looked at the CD repair FAQ (very informative!), and I have done the following:

1. I have cleaned the lens with isopropyl alcohol.

1. I have discovered that the laser pickup WILL NOT re-center itself under any condition if I manually move it away from the motor spindle.

2. As far as I can tell by simple observation, the laser pickup DOES NOT light up under any condition. (I looked at the lens from an oblique angle about 6 inches away from it in a darkened room.)

1. I have verified that the lens drive motor AND the CD spindle motor do work OK. (I unplugged each motor's wiring harness and applied a small DC voltage.)

2. I have cleaned the contacts on the little leaf switch that opens and closes whenever the CD drawer opens and closes and verified that the switch is opening and closing normally.

1. I have verified that all wiring harness connectors are clean and well-seated.

Somehow, this player simply will not turn the CD playing circuits on when the drawer closes. I think the logic IC is fried. Oh well, I needed a few electronic parts, so now I have a whole box full!

Thanks to everyone for your help....

This may be the main problem. This is usually done regardless of the state of the laser pickup. So, either the sensor isn't working or there is a problem with the motor driver.

So, not even a tiny red dot?

Did you reset the sled to the center? It might not light up if the sensor thinks it's starting at the wrong place.

Else, there is a problem with turning on the laser. You did say it recognized the ToC once, right? So the laser itself works.

Could be a bad connection/bad cable.

Doubt it. :) Certainly possible, but the most complex most expensive part really isn't likely to be bad.

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Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs.

OK. Well your biggest clue there is that the laser never homes under any circumstances. This means, probably 75% of the time at least, that the problem is power supply related. I don't know if on that model, any psu voltages are silk screened on the board by links, test points, or connectors. If they are, look for the 5v that feeds the system control logic, and the 8v (typically) that feeds the motor circuits. It's usually called something like "+8M" or "M8v" or "Mot8v". If you can't find any markings, look for 3 terminal monolithic regulator ICs - like 7805 and 7808 and 7909 and so on. On all types, positive and negative, "out" is the far right pin with the heatsink away from you. On 78 positive types, "in" is the left-most pin. On 79 negative types, it's the centre pin. Check for correct output voltage, and that the voltage is 'clean'. Failure of the little decoupling electros by the sides of them, can cause them to oscillate, which wreaks havoc in the following circuitry.

If any have low output voltage, check them to see how hot they are getting. If they are cold, and the input voltage is at least 15% above the expected output voltage, suspect the regulator itself. With the 5v logic supply, it is *particularly important* that it lies between 4.8 and 5.2v, and preferably as close to 5v exactly, as possible. Also that it is very clean (check with a 'scope).

If it doesn't have 78 / 79 series regulator chips, look for regulator transistors, which may be either flatpak types, or those taller than normal D-line types (like a big TO92 package). Look particularly, for any where the pcb underneath looks scorched or discoloured.

As another bit of a test before you start digging in to component level, you can try having a look at the voltages on either side of the 'tray closed' switch, and just make sure that they do change when the tray *is* fully closed. Also, you can push the laser all the way back home by hand, and just see if the laser does then burn, and the focus seek operation starts. Should be enough to get you going.

Arfa

Arfa:

You hit the nail on the head. The problem appears to be related to the power supply...or at least to a component downstream from the power supply.

Right next to the connector that leads to the laser assembly, one of the contacts is labeled "5V". Measuring this contact gives me less than half a volt under all circumstances.

This 5V contact leads directly to the collector of a 2SA1270 transistor. The transistor checks out OK, although the same half a volt reading is measured at the collector. There is a jumper wire that leads to the emitter of this same transistor. It is also clearly labeled "5V", and it measures a healthy 5.08V.

The base of this transistor is connected, via a 10k resistor, to the middle lead of a very small transistor with "C114" on the case. If it is a 2SC114, I cannot readily find a replacement for this transistor, and I cannot find a datasheet, either, so I don't know how to check this transistor. It gives me weird readings whenever I test it in standard NPN or PNP pin configurations. IT DOES NOT SEEM TO BE DEFECTIVE, HOWEVER, because there are several "C114" transistors and they all give me extremely similar readings whenever I attempt to measure them in standard NPN and PNP pin configurations. There are also a couple of 100uF/16V electrolytics in this circuit used as couplings to ground, but they check out fine with my ESR meter and my analog ohmmeter.

I am going to attempt to keep checking upstream to see where things break down.

Hmmm. I haven't specifically looked up this transistor, but I think you would be correct in assuming that it is "2SC", in which case, it is NPN by default. However, that said, if the readings are 'odd', and compare similarly with others of the same number, then it's probably one of the types which has internal resistors connected to some of the terminals - these are very common. From the configuration that you are reporting, I would suspect that this is in fact a switch circuit, probably driven by the system control micro, so it may or may not be faulty. At an 'experienced guess' I would think that you would be expecting to see some change in voltage level at the 10 k resistor, and further back at the base leg of the small transistor, as a result of shifting the unit from some quiescent state to an active one i.e. from "standby" to "on" or from "stop" to "play". If you do see such a level shift, but the 5v never appears at the output of the

2SA1270 (which will be PNP, incidentally) then you do have a problem in this circuit. If you're brave, you can always link the collector of the 2SA to its emitter, thus 'simulating' the switched on condition, and see what happens. It will at least tell you if the primary problem is anything to do with this voltage apparently being missing. If you're not quite brave enough to do it by putting a screwdriver tip across the transistor leads, solder a 1 ohm fusible resistor across there.

Arfa

The "114" is indeed a digital transistor, a DTC114.

Mark Z.

Thanks Mark. There you go then. Mark confirms that it is a DTC114 digital transistor, which means that it is a conventional bipolar type, but with internal resistors. This all but confirms what I was thinking, and that it is a switch stage for a 5v rail to somewhere, derived from a permanent 5v rail, that you are looking at.

Arfa

Arfa:

Are you saying that I should suspect the DTC114 or the 2SA1270? Or something else?

I'm betting on the DTC114 being the culprit.

Well, it may be the culprit, but you did say that it seemed to compare favourably, with others of the same type. It should be easy to check if this stage is working or not, with a couple of voltage measurements. Just check at the base of the DTC114, to see if the voltage there ever changes when you alter things i.e. open and close the drawer, hit the PLAY button, hit the STOP button, go from standby to on etc. If the voltage does change, then check at the collector or emitter, and see if there is a corresponding, or inverse change there. If not, then the DTC may well be faulty. If there is never any change at the base of the DTC, then this is likely not the stage that's at fault, and it's probably just not being switched by the system control micro, as a result of some other condition not having been fulfilled. As I said previously, you can always 'force' the stage, and make the 5v appear on that second link ...

Try to be logical with the fault location process. Try to understand how the stage that you are troubleshooting works, and then formulate a set of tests that will prove out the various sections of it. Only do one test at a time, and analyse the result against what you were expecting. Use the result gained to re-evaluate the next test you had planned, and see if it is still valid, or could be altered to provide you with more information, based on what you've just found out. Try to remember that fault finding is a dynamic procedure, which produces 'branches' and deviations from a basic 'model' that you work out for your tests, at the beginning.

Arfa