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MDS-JB980 Erratic Laser Issues !

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Unfortunately the laser of my beloved MDS-JB980 seems to have a mind of its own at times and is losing its position whilst reading the disc, as well as making a clicking noise. It reads and plays a prerecorded disc for the most part but even then wanders off course sometimes. The unit hasn’t had a lot of use. Any thoughts ?

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(Waffle, not a solution...)

There is something weird going on at the moment... all these machines "suddenly" not working.

On my side today, the CD section of my Tascam MD-CD1 has just stopped working - I just played Toto IV quite happily. That finished and I put in another disc. Nada. Won't read it. Won't read anything. Huh? Fortunately the MD section is still working, so I'll use that - which is what I'd prefer to do anyway :-)

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Is your MO disc an 80 minute one? Try a 74 minute one, the track pitch of 74/60/CD discs is the same. It's finer on 80 minute discs.

I know that is no kind of solution but it's probably reinforcing the "I'm getting just very slightly stuck" symptoms - as opposed to "my laser is broken". We don't want to go there (and we do have a tendency to immediately jump into the "my laser is broken" "diagnosis").

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You do know at this point I'm going to suggest re-seating the two ribbon cables don't you. Well, it brought my 530 back from the C13!

Not convinced it's this but stranger things have happened if there is nothing else obviously bust!

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27 minutes ago, kgallen said:

(and we do have a tendency to immediately jump into the "my laser is broken" "diagnosis").

So true ...

I remember when I made my first LPM and had the first successful repair with the help of it. It was such a liberating feeling, that I immediately fell under the "law of the instrument" (aka: "if the only tool you have is a hammer, you tend to treat everything as if it was a nail" - although we used to say this proverb slightly differently: "give a moron a hammer, and ... etc.")

:-)

 

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The drives I believe are interchangeable in these two variants of the same product. However the ribbon cable result is interesting.

Hopefully you didn't overly handle the exposed connections at the end of the ribbons when doing this. Unless you do some crazy static electricity dance first, being sensible here shouldn't result in any ESD damage. But there are CMOS-based chips at either end (on the drive and main PCB) and some connections do go directly to inputs (albeit usually via series termination resistors) so we should take reasonable care not to cause irreversible damage to the devices.

Given this has changed the prognosis, maybe we should explore this a little more for oxidised terminals. Probably at this point lots of other Forum members are slapping their foreheads, saying "oh gawd he's off on his ribbon cable thing again". But anyway, if you do have any isopropyl alcohol and some cotton buds, with both ends removed, maybe you could give the exposed contacts a clean. Also if you can do this without creasing them, I'd insert and withdraw them a couple of times into the sockets on the drive and main board. We're trying here to scrape through any oxidation that might have built up. Let's not kid ourselves here, most of these machines are around 20 years old if not more.

However what we don't want to do is make that machine any worse, so please take care. If you have an antistatic wrist strap or can grasp for a few moments a grounded piece of equipment (like the case of a desktop PC- a non painted part) then all the better. So long as you don't have any existing un-tripped earth faults in your house that is!

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13 minutes ago, kgallen said:

Probably at this point lots of other Forum members are slapping their foreheads, saying "oh gawd he's off on his ribbon cable thing again".

Well, ribbon cables can trick you in several ways. It must became a routin to always check them first.

Here is one example - I reseated this one a quite few times, but the fault did not want to change. It took me a while to actually look at it, not just reseat it. Visual observation can also help a lot.

ribbon1.thumb.jpg.5633c7f004b1028c2fe7d3c9f2be6d7c.jpg

 

And I would like to add another one on the "broken records" list: do not move over to the next thing to check, before you are done with the previous one. You must conclude that it was not the cause, and prove it for yourself, then you can move on. Otherwise, jumping back and forth between different potential causes might lead to a total chaos in your head, and would definitely not help to find the way out. You just stand there and can't see the wood for the trees.

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On 6/5/2020 at 7:16 PM, MD4ME said:

I don’t have any isopropyl alcohol, is there another equivalent ?

Vodka? :-)

No, I am serious. Certainly not "equivalent', but it is a fairly "clean" spirit, with relatively high content of alcohol.

Anyway, isopropyl alcohol is there in several other liquids around the household, like rubbing alcohol, eyeglasses cleaner, window cleaner, stain remover, etc. All these materials may do a good cleaning on those contacts. Mineral spirit (white spirit) would also do it, though the odor is not that good, and probably not the best for such delicate parts.

And a trick: sometime I use ordinary eraser to remove the oxides from those galvanised contacts. Carefully though, not to wrinkle the ribbon itself.

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I’ve tried cleaning the ribbon cables with alcohol and an eraser but alas I’m getting the same erratic behaviour. As I mentioned earlier I also have a MDS-JE480, would it be possible/wise/a good idea to swap over the whole laser & loading assembly from either the 480 into the 980, or vice-versa ?

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If you take due care, that should be very straightforward to do. I've lost track of how many times I've moved MDM7-series drives between my various E10, E12, JE440, JE480 machines trying to debug an issue! When you do, the machine should flash "Initialise" on the display a couple of times when you first power it up.

Mains lead unplugged of course for this and avoid getting your hands all over the PCBs. Make sure you use the rubber mounts and shouldered screws from the host machine in the host machine.

As the 480 and 980 are probably much the same inside, for now lets say you use the ribbons from the 980 and just move the drive. That way, if it works we know the ribbons from the previously-faulty 980 are indeed in working order.

Good luck!

Kevin

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Thanks Kevin, I’ve swapped the drives over and the 480 drive works in the 980 whereas the 980 drive displays the same faults in the 480. So the problem is definitely in the 980 drive somewhere. I’m happy to leave the 480 drive in the 980 if there’s no difference to the performance, but why is there 2 little red (earth cables ?) on the 980 drive whilst only 1 on the 480 ?

What I should I be looking at next regarding the fault in the 980 drive ? Cheers.

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You can transfer over the chassis straps from the 980 drive to the 480 if you want. I don't have those on most of my machines (never there not that I've lost them). At some point Sony must have decided they wanted another common return path. The other 0V returns are on the ribbon cables and by that they are a relatively high impedance connection. That is always a bad situation for a reference connection. So I guess they added those flying leads to try and create a better return paths for the various currents. There are of course motors on the drive which are relatively electrically noisy. You don't want that electrical noise getting into your control systems or audio paths, so having a low impedance return path can help a lot there. I don't have many machines (even my "Pro" E10 and E12) with these chassis straps. I do have them in a couple of the later-but-cheaper 4xx models I bought for spares (then got them working with a belt replacement!). Sorry, went on a bit there!

As far as I know the drive from the 480 is identical to the drive from the 980. I'd have to check the SM but they are the same series (note this wasn't always true in the early days, a JE330 is like a JE520 not a JE530).

Play with the 980 drive in the 480 - rather break the 480 than the 980! Worth putting a label on the good one, you don't want to "investigate" the good one and break that.

My suggestion - look for something silly/trivial. Do a thorough visual inspection of the broken drive. Compare carefully to the good one. Check they have the same springs, that the gears seem to be "at rest" in the same positions, that other movable parts look like they "rest" in the same position (rotation/linear position).

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So far so good with the transfer ! I was rummaging around in the loft and found another, rather battered, 480 deck, so I’ve substituted the drive out of this into my back up deck.

A couple more things to mention, whilst scrutinising the various drives, with my untrained eye, for differences I noticed the one 480 had what appears to be a ‘plastic’ component on the circuit board whilst the 480 and the 980 had a metal equivalent ! (See photos). Also, is there any reason, other than ease of manufacture, for the original belts to be square cross section whilst the replacements are round ?

Thanks for all the help !0549D8BE-FB2D-484C-A4AC-8F820E3C5248.thumb.jpeg.3825760ee5ccf6866766092056a5e0da.jpeg9F9FB1D0-8F1D-4403-B0DD-BDB118190936.thumb.jpeg.32493b3588a2b74cfde1a4e7d622ba15.jpeg

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27 minutes ago, MD4ME said:

Also, is there any reason, other than ease of manufacture, for the original belts to be square cross section whilst the replacements are round ?

Both are electrolityc capacitors. In mass production it is not unknown that different batches use sometimes different components, as there are always several part suppliers that serve the OEM. Also, if there is a slight design change, for any reason engineers felt they needed, some parts can have a somewhat different specification, but essentially the part is the same. You can compare the P/N of the BD board, and see if one is a later version. As long as only the last two digits are different, they normally interchangeable.

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6 hours ago, MD4ME said:

So the problem is definitely in the 980 drive somewhere

No doubt. We began working on your 980 drive :-) , and we did it for a reason :-) .

6 hours ago, MD4ME said:

What I should I be looking at next regarding the fault in the 980 drive ?

I still put my two cents on the sled problem, that I began with. That rattling noise on both of your videos is definitely telling that to me.

The second video is more "verbose", because it shows the OP tries to play a track, then reverses back to the TOC as it did not find it, so seeks for the information again, but it could not properly read the TOC either, so keeps trying. That noise is very similar to when the sled moves back to the beginning of the dics and the gear jumps over one tooth of the rack. I have seen several similar cases. Until you don't pull the sled off the drive and take a look, we cannot really exclude this possible cause.

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I think the former is aluminium electrolytic and the latter tantalum. Probably a bulk supply decap so their other electrical differences are less critical. Otherwise as @NGY says. Look different values though, 39uF (16V) vs 22uF (4V). 

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