Sony Minidisc decks with C13 Disc Error - my learning path

[NGY 26]

UPDATE: I have changed the original title "MDS-JE510 Disc Error" of this thread. I intend to collect my C13 Disc Error cases into one topic.

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MDS-JE510

What a silly error I faced today...

Yet another 510 that came with the known troublesome load/eject. I have already fixed half a dozen of 500 or 510 with this problem (or sudden switching on from standby, or disc error upon loading a disc - as these all root in the same issue), so I performed the usual routine (fairly straightforward fix, but requires a complete strip down of the drive, and some delicate repair work on miniature parts). When completed, I put the drive back into the deck and powered up. Upon inserting a disc, I heard it spinning up, so far so good. It tried to read the TOC a couple of times, changing revolution and seeking OP, but then it spat out the disc, again with "DISC ERROR". OK, let's check the laser I thought, but both the settings and the measured mW values were spot on. Then I checked the error rate, and it was very high - increasingly higher in the MID and OUT ranges, that called for a deeper inspection.

I removed the lid to take a look at the drive. It became obvious, that the disc hit up and down quite a bit, ~2 mm on the edge. I thought it was my much (ab)used test disc. With a known good disc, the same happened. First I suspected the axle of the spinning motor, whether it got bent once the last disc the deck had eaten, was pried out violently. But the shaft was running true. After trying several discs, and most of them got ejected with the error, I took a closer look at the magnetic hub that holds the disc in place, and found this: a little bulge, probably some burr left by injection molding of the part. Once I cut this little piece of plastic off, discs began running way smoother After properly adjusting the traverse and focus bias I rebooted the deck, and voila, no more disc error, and it plays/records as it should.

But what bothers me, how on earth this deck had worked so far at all? Or, is it that the laser tracking/focusing mechanism did compensate for the rocking discs, but only until it got somewhat "tired"?

  . 

[NGY 26]

MDS-S40 (apropos of the similar case of an MDS-JA22ES)

This is just a link to a C13 story in another topic - everything is detailed there, so I would not duplicate everything here.

Essence in a couple of words: a broken part in the OP positioning mechanism caused the error.

 

[NGY 26]

MDS-JE520

Yesterday night I played with a faulty deck, and here is what I found. I bought this MDS-JE520 on ebay for parts originally, it was fairly cheap, so I did not mind stripping it down. But as usual, first I wanted to understand, what is the cause for the fault. The deck would not accept any discs, after loading one, it would try to read it, but then it would eject with C13.

I had already some idea, that there can be multiple reasons for a deck rejecting a disc, however, here came another one I would have never thought of.

Before jumping on it, here is a little puzzle: can you spot any differences? Left one is the drive of the 520 exhibiting a C13 error, right one is another 520, that works OK.

  . 

 

Yes, one part is missing, a spring! Here is the "difference":

 

I had no clue, where actually the spring was, because it was not inside the deck when I opened it. More than that, how could that spring jump off? It takes an effort and a tool to take it out of its place.

OK, but then what's the problem? It looks that the drive loads the disc halfway only, and cannot lower it into its nest, because this spring is responsible for holding the loading tray in the required position. Once the disc is not fully loaded, it would certainly not spin, and the laser would not read anything - disc error, eject.

On the left the disc is stuck halfway, on the right it is properly loaded (well, I did it manually, for the sake of the photo):

  . 

 

For a quick test I lent the same spring from the other 520, and presto, the C13 error disappeared!

Now, how can I destroy this unit for parts, when it is in full working order :-) ?

 

[Jimma 4]

It looks like you're going to have to keep it in one piece and just welcome a new member to your MD family:)

[kgallen 5]

This may be an "old" thread, but I'm "Liking" it because I like the simplicity of the diagnosis and the fix. We all need to remember that "laser broken" is not the first thought we should EVER have! Good one @NGY, thanks for the cross-reference link that got me here.

(And also, as my 520 was my first "MD love" I'm happy that this 520 is also still alive and well...)

[NGY 26]

We have seen here on the forum quite a few C13 errors recently. There is one thing that is more true than ever before: lots of possible causes can led to the actual C13 error (or "DISC ERROR" on certain models). For this reason, there is no generic recipe, how to solve a C13 issue.

I decided to post here my silly little "itinerary". This is not a magic formula, not even a nice, polished, completed flowchart. It is just a brief list of steps and comments I collected based on previous cases (mostly Sony MD decks), and that I normally follow when facing a C13.

Although this text below is still in "rough" format, I tried to build up a - sort of - logical order, coming from trivial to complex, from "outside" to "inside", from easy to hard to perform. Some checks do not require any tools (OK, maybe a screwdriver), while some do require at least a DMM and a soldering iron (with adequate soldering skills), and as soon as one deals with the OP, those special tools are a must.

I encourage you to add/comment based on your experience.

C13.txt

[kgallen 5]

Maybe I missed it. I would add that motors and switches can be checked with a DMM without desoldering from the BD. Motors are driven from H bridge drivers so the motor is not in parallel with any low impedance and they are single winding motors not steppers. Hence DMM across the motor contacts should measure a small number of ohms (don’t know exact value, from single digits over about 4 to a few 10s of). Switches on the BD just pull to 0V against a pull up resistor so again a DMM across them should go from open circuit to very low resistance. 
 

Talking here for MDM5 and MDM7 but other drives are likely to be similar. 

[NGY 26]

Thanks for your additions.

3 hours ago, kgallen said:

motors and switches can be checked with a DMM without desoldering from the BD.

If I may, I cannot 100% agree with this part (noting that I did not write that switches should be desoldered, except the protection switches, and those only in order to remove the BD when needed).

In essence: I cannot make sure if someone follows my "advices" here, cannot go wrong and make a bigger trouble, but my  intention is to reduce the risk as much as possible.

An "amateur" might not be fully aware of all the risks of poking around on a PCB, with a "loaded gun" DMM. What I mean is a DMM provides a certain DC voltage (in the range of 1...3 Volts) on its probes for resistance (and continuity, and diode) measurements. A wrong pick with those probes can burn vital components. It can be the voltage level itself or a reverse polarity (or ESD related).

The switches are directly connected to the respective legs of the main system controller IC. Although the I/O ports of the cpu are certainly able to handle bidirectional voltages and currents (to certain levels) by design, my recommendation to those without such a deep technical understanding is do not touch the BD with a DMM in resistance (continuity, diode) mode. Luckily, the position switches are on separate boards on most of the drives but the MDM-7 variants, therefore no soldering is necessary to test them safely, enough pulling the respective cables out. In case of the drives with the switches directly soldered on the BD board my recommendation is using an ESR meter. Why? Because ESR meters work with very low voltage signals (couple of 10 mVolts only), that is way too low to result any semiconductors to "switch on", thus risking a potential silicon damage.

Regarding the spindle motor: I agree an H-bridge drive would not influence the resistance measurement of a DC motor's coil (as long as we can exclude the fault of the driver IC itself). Also agree that these DC motors are simple and very robust. My recommendation for testing a motor is still desoldering and probing it from an external power source (the best would be a PWM generator, but let's just stay on the ground of the amateurs :-) ). Based on Jim Hoggart's notes, even with a proper (looking) ohmic value that motor can still have a fault (as he wrote once, "a blind spot", if I recall it properly).