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Ebay resto part xxxx MDS-JB920

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M1JWR

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bought a cheap 920 off the bay to play around with, it had two broken feet on the disc drive, i have successfully fixed those, however another problem exists, and just looking for a bit of confermation, i am not fermilliar with 5a drives, more fermilliar with the 7a's as you all may know.

the player plays fine, it appears to record as vu's register, when the recording is done it wont play that perticular track, it may register one second in every 20 seconds in real time, no output, when i eject disc it will erase disc after toc writing, infact if other tracks are on the disc recorded by any other machine it will erase those aswell, i take it the over wite head is shot.

i take it also same units as  je330/520 etc

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In my (limited) experience, a head is busted or not. What sounds to me off (here) is mechanical alignment, sled motion, head updown, etc. It can't exactly be the OP wandering off track as it wouldn't play, methinks. There's really nothing to break (other than it being bent out of shape), so I would be starting to look at the little motor and the gears of the head lifting mechanism (vertical stepper).

I will defer to Kevin or Gyula (NGY) as to how to diagnose this. Jim, where are you? All the customers we coulda sent you........

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5 hours ago, M1JWR said:

the player plays fine, it appears to record as vu's register, when the recording is done it wont play that perticular track, it may register one second in every 20 seconds in real time, no output, when i eject disc it will erase disc when toc writing,

I am neither Kevin, nor Jim :-), but here is where I would begin:

- check how much did this particular unit run (service more, error dp mode, total rec/total play hours) - this would give an idea, whether or not the "tiredness" of the OP is an immediate suspect

- lifting the top cover, visual inspection of all moving parts of the drive, the OWH at very first, but just as well the OP, the gears, etc., as Stephen already suggested

- before going deeper in to disassembling the drive, gently clean the OP with some propanol and a Q-tip, and do a quick write/read test

- pull the drive off the chassis, on the underside there are 3 screws that hold the BD board (incl. OP/OWH/sled) in the drive frame. Lift the board assembly (remember the holes for the screws), and check the toothed rack that moves the sled, if all teeth are there and in good shape, and that the spring is also there for the white part of the rack

Once you are here, please get back to us with the result.

 

My first feeling: If the deck attempts playing back the recorded track, and seems it keeps trying, the OWH might be just good (though the "blank disc"  could be a sign). If all above checks were OK, then laser is next on the list. Can be a focus bias problem, also a tracking problem, as Stephen mentioned. Or, the laser diode is just worn to the level it cannot emit enough power for writing. This would turn out from measuring the actual IOP values for both modes. But when you are at this stage, you may need some special tools to continue, without "flying blind".

Hopefully, the variable resistor on the OP had not been tampered with (some people try to "revitalize" dying lasers by turning it down, that is the fastest way to kill the laser for good).

 

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hi, think ive found the problem, at the end of the owh its suspended by two thin bits of, i'll call it wire

one is broken, maybe above my soldering capabilities, even then it would never be right

the other details are as follows

total record time 6h

total play time 164h

iop 58.8

laser power 0.9mw$10

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Great you found the cause and it is - relatively - easy to fix. With a weak laser it would have been a much tougher ride.

See some photos below, how I repaired a fully broken off OWH head piece. If only one leg/wire is broken on yours, you will be able to solder it easily. All you need then is to gently align the repaired head that it lays flat on the disc surface, when lowered in recording position (first I use another OWH to compare with - as on last photo). It will do fine - the one below on the photos serves its owner since about three years by now. (I have done several similar fixes, and they all hold ever since.)

As for your laser age, this one is a slightly used machine, great buy then.

As for IOP: I guess you read it from the service menu. Just for future reference: that value is not necessarily the real value, it is just a note, after previous (or, actually first) fine setting of the OP. Nonetheless, you won't need the actual IOP value for quite while.

 

And the promised photos:

10140.jpg   20137.jpg   30152.jpg

40160.jpg   50638.jpg

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I’m no use round here - @NGY is your man! My only suggestion would have been to carefully measure continuity of the OWH but since by inspection you’ve seen the lead frame is indeed fractured then you’ve done the job just fine with the excellent analysis equipment installed in your head! Hope you can fix it - interesting to see the OWH strips do take solder. Depending where the break is, you might need to separate the plastic parts away to avoid melting or deforming them. Then maybe - advice from @NGY needed here - lay a short length of copper wire across the break and solder either side. Tinned copper wire if you have any, if not maybe a single core from some small CSA twin and earth cable. 

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this one maybe more difficult than those in the pics as there is the end piece then the main part, if you have bad eyesight like me you would think the end piece is suspended sorta thing,

so when you see it from the side there is a small gap that is where one of the broken bits are, wearing many sets of specs and a magnifying glass i can just see where its broken from and the end is in the plastic main part, i wonder if i could melt the end a little where it joins onto as that end is broken flush,  i have removed owh now anyway as i think the only way is to get something soldered there and have the gap as close as possible match to the other side, or words to that effect

thanks for giving me some good ideas

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1 hour ago, M1JWR said:

melting the ends is what looks like youve done

Let me make it easier for you (I did not want to go into details before you decided you give it a try, not to drive you nuts :-) )

What I actually did was I very carefully blanked those wires mold into the plastic legs, with the use of a very sharp scalpel. Very carefully, not to cut/break that thin wire, and only 1 mm, max. 1,5. Then each ends (four in my case, 2x2) I scraped the surface before properly "wetting" with solder. If you have some good quality flux at hand (like used for soldering smd parts), dipping the ends into it would help a lot.

Here comes the hardest part: use a piece of rigid carton (beer coaster for instance :-) ), and stand the OWH on it like if it was standing on the sled. Use some adhesive tape to fixture (or even you can try to use its original screw, first piercing a small hole into the coaster with a strong needle). Next you align the broken part, putting layers of paper under, until it reaches the "official" position, preferably parallel to the base. Use again a small piece of adhesive tape (here I normally use painters' masking tape, for it leaves less glue residue on the head, plus it will not melt from the heat of soldering).

Now, if you did it right, the broken ends of the wires are properly aligned, a minimal gap of 1-2 tenths of a mm is not an issue. Use the thinnest  soldering tip you have, like a needle, literally. If you don't have one, take a piece of regular copper wire (1,5 ...2,5 mm2, that is 16 ... 13 AWG, sort of ...), and very tightly turn it around your soldering iron's tip. I mean, before you turn it on. Then sharpen the free end of that wire with a precision file. "Wet" the newly made needle tip with solder. Leave a small amount as excess, like if it was a pin head. Touch this small "ball" of solder to the aligned wires, where the break line is. If the wires were properly cleaned and flux on them, you will see the solder running up on both. Immediately remove the iron, and don't touch your OWH until it cools down.

You are done.

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1 hour ago, M1JWR said:

might take some time

Sure, no rush. And you may want to practice first on two small pieces of thin wire, as Kevin suggested, aligned end to end (use the masking tape here too).

I found another photo for you, I think it shows the actual soldered joints better:

70149.jpg

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ahh, i havent done the deed yet, i am not expecting 100% with my soldering capabilities, they are quite good, i am gonna find out how good, will be a few days as i have ordered scalpel and some flux, mail here is slow because of the carona thing, so could be week end when i get to it.

ofcourse i will keep my eye out for a donor, just incase

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well, i had a go, followed instructions as much as possible, was doing quite well until another little bit came off, i was using 3 pairs of specs, i think that would be  +8 mag and a strong light, thats when i was scraping a part of it, so had to replace it with a bit of thin wire, i realise it would be never right after that, managed to solder it together, it looked as close to correct as could be, compaired to the other side and checked continuity and that was there, so ok try in the player, and the result was it is doing the same as before.

plan b, find a 330 or similar, with c13 or something as a donor, i know i have a good laser in this one, there is  one or two on the bay at the moment, cheers gyula, it was worth a try.

just a basic repairer at this end !!!

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You gave it a try - big respect.

 

12 minutes ago, M1JWR said:

plan b, find a 330 or similar, with c13 or something as a donor

The 330 is a good choice, cheap machine, quite frequent. You can go for a "fully dead" one, just ask a good photo of the OWH from the seller, to make sure.

The 520 or 530 also would make it, though used to be a bit more expensive.

 

11 minutes ago, M1JWR said:

 i know i have a good laser in this one

Your total rec/play hours certainly support this.

Nevertheless, if you keep getting the same error after fitting an intact OWH, I would stop there and measure the actual IOP against the actual laser emission. But cross our fingers you won't need to go that far.

Either way, please keep us posted on the progress.

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hi

i think there is a catch to looking at the owh on one of those 5 series drives if i am looking for a "spares or repair" and its dead or c13, the owh is fairly well obscured by the drive unit top part, lots of sellers that have them like this wont have any discs to test so they can show you. as i can see from this machine you can only see it when a disc is in situe, and a lot of them dont give a toss anyway, they will go "theres that old minidisc player in the garage, bang it on ebay and get a few quid" its usually the case as we say in the uk risk it for a buscuit, to get one as cheap as possible, i have written down which other players use this drive unit, 330,520,s39,s40,s41, and m100 whatever that is, but ,yes 330 and 520 most common, i have in another thread a 940 that had a shot drive unit, it did have a good owh though, i bought a 470 as donor, swapped units then found another 7a unit with a shot owh, installed the 940's old owh to that and put it into the 470, result 2 fully working players.

as for eyesight i think i will stick to oldish amps nice big components in those !!!

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8 hours ago, M1JWR said:

i have written down which other players use this drive unit, 330,520,s39,s40,s41, and m100 whatever that is

The S39 has an MDM3 flavour of drive, the OWH is different from yours in the 920. Rest on your list are OK for this repair.

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my mistake about s39, ive just bought a 520 for £35, spares or repair inc post, standard thing here, switches on says no disc and seller has no discs to test, and looks like its been up a loft for 20 years, if nobody has been inside it then fingers crossed !!!

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thought you had a 530 kevin, anyway transplant complete, now have a 920 in full working order and 520 will remain as looks like play only until summat crops up whenever that may be, also the 920 shows the 520's record and play time totals, i did not think it would do that.

got an old cdp 970 cd player to look at next, skips if you tap the top of front facia, its a big heavy old beastie, the cd tray is made of aliminium, dont make them like that anymore !!

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21 minutes ago, M1JWR said:

the 920 shows the 520's record and play time totals, i did not think it would do that

I guess you replaced the whole drive mechanism, didn't you? Error dp information is stored on the BD board.

I would love to see whether or not marrying the "bad" drive and the good OWH makes now the 520 recording. It would confirm that only the broken OWH was the cause, or something else. Just to give a heads up for later visitors, what to look for in similar cases (besides swapping a complete drive :-) ).

 

21 minutes ago, M1JWR said:

transplant complete, now have a 920 in full working order

Congratulations anyhow, the 920 is a nice QS machine.

 

 

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i did have a 470 drive with a knackered owh once and put on a good owh from a knackered drive with positive results, however in the knackered drive i dont think the bd board was at fault, it was mechanical, dont know it that counts.

diddent kinow the 920 had 2 current pulse dac chips in there, no wonder md sounds better than you think it would.

yes i swapped the whole thing over, maybe next time.

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11 hours ago, M1JWR said:

thought you had a 530 kevin

I've got a 520 and a 530 (amonst a lot of others!). The 520 was my first MD "baby" (receipt attached, oops, sorry it's so big!). The 530 was purchased a couple of years back from eBay with the aim of using MD again at my AmDram society (which, due to the 530 issue, got me into Tascam MD-350, then Tascam MD-CD1, then Sony MDS-E12 and E10... which then got me into 440 and 480... which then got me into... the rest of the list on my profile!!!).

11 hours ago, M1JWR said:

anyway transplant complete, now have a 920 in full working order and 520 will remain as looks like play only until summat crops up whenever that may be, also the 920 shows the 520's record and play time totals, i did not think it would do that.

Excellent! As @NGY says, the BD board (EEPROM) holds this data - along with (I believe, possibly disputed) - the Iop settings for the laser. This is why you can swap drives between machines and the main PCB CPU knows how to configure the BD.

IMG_4261.jpg

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1 hour ago, kgallen said:

attached, oops, sorry it's so big!

I thought others might find this little hint useful too.

There is a nice feature of this forum engine: after you attached a picture and inserted into the text, double-click into the photo (the inserted "copy" of it), that brings up a configuration window. There you can set the size of the thumbnail, how the picture will appear in the post. Say 120...200 pixels wide (heigth follows it proportionally), and it still gives an idea of what the photo is about, yet the post remains compact, easier to view, scroll, etc.. Then readers just click on the thumbnail, and can see the picture in its original size.

 

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8 minutes ago, NGY said:

after you attached a picture and inserted into the text, double-click into the photo (the inserted "copy" of it), that brings up a configuration window. There you can set the size of the thumbnail, how the picture will appear in the post. Say 120...200 pixels wide (heigth follows it proportionally), 

Done. Thank you!!! :-)

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1 hour ago, kgallen said:

the Iop settings for the laser

I don't want to seem like a stickler, or doing any hairsplitting here, so please don't take my words below anything like that. And I know you had "laser power settings" on your mind when writing the above.

I just felt it was important to mention, that  - at least on the Sony MD decks I met so far - there is no such thing in the service menu, as IOP settings for the laser. IOP value is more of a measure (i.e., a "consequence" ), and not really a parameter or variable one can modify or pre-set in a menu.

Here is a short explanation on this (with some addition here), should anyone be interested in details.

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17 minutes ago, NGY said:

And I know you had "laser power settings" on your mind when writing the above.

Indeed, what I meant was "the information the main CPU needs to use the BD board is contained within the EEPROM", which is what allows us to plug-and-play drives. i.e. we don't need to go in and change and settings or reconfigure the main board when we transplant in a drive from another machine.

I don't have a memory map of what is in the EEPROM, I just know we can "plug-and-play" - or if nothing else we seem to be able to do this without damage! Certainly the main CPU reads this EEPROM over I2C early on in boot (I've seen this on my protocol 'scope on my forever-faulty E10).

@NGY your information and experience is invaluable, reliable and well-founded. Please "split hairs" (indeed I want you to) whenever needed (at least on my posts!!!) - this is a learning experience for me! :-)

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  • Richard changed the title to Ebay resto part xxxx MDS-JB920

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