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Mini disc repaired but keps saying PROTECTED

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jonmig

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HI gUYS

I own a virtually unused MDS-J3000ES , unfortunately just the other day I got a disc stuck in the transport mechanism ,after managing to get it out I unfortunately damaged the pick head therefore I purchased a donor unit off Ebay and replaced the head however taking the mechanism apart seems to have caused a problem as even though the unit plays and reads the discs ok it just will not go into record mode anyomore and all I get is the PROTECTED warning in the display, I have checked the microswitches cleaned the laser but for some unknown reason it has developed this fault , is there anybody that knows these mechanisms inside out and can point me in the right direction please of why I keep getting this error..

 

kind regards

Mike

 

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If it plays ok, the problem is certainly with the write-protect mechanism, which is mechanical, and relies on the detection of the gap in the MD case. You will have to make sure that the closure of the microswitch does its job in the circuit. Sorry I cannot be more specific than that but you'll need some electronics experience with voltmeter and/or soldering iron, most likely.

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Thanks sfbp , I notice that there are 2 micro switches where the write protect part of the md case rests not sure why there are 2 one is slightly shorter than the other ,I did think that the casing was not touching these at first but I can see that they are flush against the corner , there are also 2 other microswitches on the left hand runner side one is near the motor which somebody said could cause problems but I've checked this one too ..and then there is a kind of slide microswitch , the pickup head also doesnt seem to engage to touch the disc but of course I guess it wont move any further whilst it is being inhibited by the protect warning circuitry ?

 

attached pics (from a donor mechanism) 

one showing the corner protect microswitches (why are there 2?)

the other showing the left hand rail microswitches what are their function?

 

Screenshot_20190322-155412.png

Screenshot_20190322-154715.png

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I think the two switches are: "present" and "protect". It's normal for one to be shorter, I don't recall which is which. You can tell which is the write protect by looking at the location of the protect slider on a writeable disk. It's just possible there's a sense for CD vs MO (the precorded disks), I am not able to look right now so relying on my memory. There's a THIRD sensor hole on 1GB Hi-MD disks to allow the HiMD units to detect that medium.

There's an interlock mechanism on portables, but I don't think you have to worry about that on a deck.

If you are not that famliar with MD, perhaps you didn't know about the write protect setting on each MD disk. OPEN means protected, CLOSED means writeable.

Keep the questions coming, I have a hunch this is solvable easily.

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hi sfbp

Yes I am aware of the holes on the MD's casing just wasn't sure why there were 2 , its a shame because this unit has been treated like gold I even flight cased it as I used it briefly for gigging back in the 90's ,it was only the other day that a disc got caught in the mechanism and unfortunately not knowing anything about the inside I clumsily tried to get it out but damaged the pickup head and also dislodged the carriage , so I purchased a donor machine to see how everything fit back and also to repace the broken pickup ,managed to put it all back together again and thought I had succeeded in the repair until I pressed the record button and nothing happened except the PROTECTED message comes up on the display...

It must be something minor that I'm overlooking here sfbp but I'm blowed if I know what ,so near but so far :(

kind regards

Mike

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I've checked all the microswitches with a continuity meter and they are working fine ,the short pin if pressed causes a cd error the long pin is indeed the protect one but still

the unit is locked out of recording mode..

 

if anybody else has any ideas it would be much appreciated  ;)

 

 

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OK, that's good, you verified that the switch works.

Next I'd be inclined to force a reinitialization (like what happens after you've serviced the drive).

Ah.... I know, you replaced the head but you didn't align the drive yet. It's not automatic. You're going to need some gear. If you don't adjust the laser power for that laser, you will blow it (literally). Just as well it's smart enough to know it needs servicing. Time to get the service manual .

https://elektrotanya.com/sony_mds-j3000_mds-j3000es.pdf/download.html

There isn't one here or at minidisc.org.

They're all the same in outline, only the details.

When you're ready to move, please keep asking....

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hi sfbp

 

Thank you for the links  ,very helpful  ;)

I only replaced the overwrite head so I would presume that the laser is calibrated correctly,  gut feeling is that its something to do with a microswitch and positoning of the cradle mechanism at certain points of its travel ,everything worked perfectly before I dislodged the mechanism and accidently broke the overwrite head as its sooooo fragile ..

kind regards
Mike

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hi sfbp...

 

After a lot of head scratching I have finally solved the problem and she is up and running again , as I still have the components from the donor player I decided to try a few board swaps I exchanged the tiny board which is on the back of the motors that has a few microswitches and this seemed to do the trick therefore I am thinking that when I reconstructed the carriage I may have damaged one of the microswitches with the carriage leg ,even though I tested it for continuity there could have been a damaged contact still ,its actually mentioned in the service manual with a warning so this is probably what happened ...

Thank you again for your kind attention sfbp I really appreciate all your help ... ;) 

Mike

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You're probably right, the OW head laser power setting is 10x the power of the read head when reading. It is the READ headpower (ie the laser) which absolutely must be calibrated within very fine limits. Conceivably differently resistive OW heads might cause slightly different results but all in all, if it works, you're in shape. Well done!

From your post which I skimmed in my usual haste, I thought you had replaced the whole laser assembly.

(updated as I must have been dazed when writing that).

 

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hi sfbp

no it was just the write head and the mechanism that I replaced with a donor player, because I didnt know what I was doing I just went in there hamfisted trying to get the disc out ,after mending it I wish I had been more careful when I tried to get it out ,but we live and learn ;)

 

kind regards

Mike  UK

 

 

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