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freddyjollo

Swapping optical units between JB940 to JB980

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To save me looking thru all the posts can any one confirm that an optical unit from a Sony JB940 can fit into a Sony JB980 and work properly. The record head of my JB980 has broken off it seems & I have a number of JB940s that could donate a drive unit. They certainly look the same physically. Buying decks for spare parts now costs too much to consider. I bought the spare units years ago for about £70 each.

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I thought the same about the various MDM-7SC drives in my Pro units (E10, E12). But there does seem to be a small difference for some reason, maybe firmware on the drive? Had similar ‘not fully playing ball’ issues with a 440 drive in a 480 (Type S) which is essentially what you have, although I was never sure if that was down to the 440 drive seeming a little fickle even in its own machine.

The ribbon sizes and positions should be identical on your 940/980 so I’d give it a try although as above x40 is not Type S. 

Otherwise see if the OWH is swappable. I think electrically it’s a 2pin header although mechanically it might be very fiddly. 

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Greetings to everyone. Hope you all had great holidays. Also, glad to see that the forum is back. Thanks to all, whoever was involved in getting it back on track.

To the OP: swapping drives between different Sony MD decks requires pin compatibility of the ribbons (and switch-board cables, where applicable) AND the same version of the DSP chip (practically the same version of the BD board). The MCU (located on the Main Board) wants to directly talk to the DSP, thus must find the proper counterpart. Type-R and Type-S devices have different DSP-s by nature, regardless those (MDM-7) drive mechanisms/OP/OWH being quite compatible.

(In this regard, whether or not the deck itself is USB controlled has less relevance, because that happens on a higher level layer, but yes, this also means that the microcode in the MCU is different too.)

If it is only the OWH that is broken off, you may not need to swap the whole drive. The MDM-7 drives are luckily "easy" from OWH (or even OP) servicing point of view. All you need to take care of (besides the usual ESD stuff) is not to move the sled out from and/or leave outside of its parking position before powering up the device again, or you may run into the infamous "stuck in Standby”.

One more thing: if the replacement OWH has a different connection cable (yellow flat ribbon vs. white or black twisted pair), you may need to do a bit of soldering work too. With that, you can even use an OWH from an MDM-5 unit.

image.thumb.jpg.9828e4c6d702b5c8d28e79bda420f5b0.jpg

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Thank you for the much more precise answer Gyula. Hope you had a good Christmas - we are all very quiet and rather lonely here, as despite no lockdown everyone has abandoned social relationships after listening to the prognostications of our top doctors. I was painting a broad picture, and it turns out that the USB devices were all CXD-2664 whereas the PS/2 devices were CXD-2662. I've no idea if the actual BOARD can be swapped though - seems much easier (!) to swap the OWH. Regardless there is likely to be at least an alignment cycle (correct me if I am wrong on this point or any other), so for those without LPM it isn't easy "just" swapping things.

My own experiences of OWH repair are in two parts: portables and decks. The portable (MZ-N505) I and a friend managed to repair, it was a nightmare of not being able to see, trying to heat solder without melting plastic, and pure fiddliness. The only deck that I got fixed (my MDM7 in the PX-3) went off to Jim Hoggarth back in the day. I vividly recall my efforts to fix a stuck MDS-JE510 which ended with it going to the dump.

There is a bright side to machines (decks or portables) with broken OWHs - they can be used to erase disks (particularly when you have a disk that won't respond to treatment due to copy-protection after transfer by NetMD).

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Thanks for the input. I think I will just pack away the JB980 until I can maybe get a replacment head cheap. Which cheaper models of sony mini disc decks would be a good donor? Other wise just keep using the JB940 decks I have as they are really good enough. I just dont like having broken things.

On another point how easy is it to swap the mother boards of the drives over. Any one ever done that?

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47 minutes ago, freddyjollo said:

Which cheaper models of sony mini disc decks would be a good donor? 

MDS-JE480 I'd expect, it's a sub-equiped 980!

47 minutes ago, freddyjollo said:

On another point how easy is it to swap the mother boards of the drives over. Any one ever done that?

Never done it but my assessment would be this is not a trivial job - mostly down to the desoldering required to remove the old one first. No doubt some have done it but to do it you'd need a donor drive and I'd just fit that one instead.

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3 hours ago, freddyjollo said:

how easy is it to swap the mother boards of the drives over. Any one ever done that?

Yes, I did, a couple of times. If you know what you are doing, and you have the necessary soldering skills and equipment, it is fairly easy. (But more difficult than the MDM-5 drives, that are the easiest to service of all, by far.)

Having said that, replacing the BD board on an MDM-7 flavour is still a "PITA". You have to strip down the drive "to the bones" so to speak, and from there multiple things can go wrong, big time. And we all know, decks with these mechanisms are the most vulnerable to our old "friend" called stuck-in-standby (or just a simple C13). And let me repeat the importance of the ESD protection measures.

Disassembly:

- lift the drive off the chassis (be gentle with the ribbons...)

- remove the top part of the loading mechanism (easiest step, even no tools needed, though a pair of tweezers can be handy),

- remove the OWH, then the sled with the OP (OK, one can accomplish a BD swap without this step, but there is a huge risk of damaging either one or both during turning the drive back and forth, upside down, poking around with a hot soldering iron, etc.),

- desolder all three motors - making sure the copper foil is not burned off of the board,

- desolder the prerecorded/writeable media and write protect tab detecting switches,

- remove one screw, then lift the board - here is "what you get":

2559.thumb.jpg.7d634b08f183e9dd90db727cefb1c075.jpg

Assembly: steps as above, in reverse direction. As the MDM-7 has all positions switches soldered on the BD board that can easily be damaged during re-assembling, you must be very careful, what part to put where, from which angle, etc.

Once you are done with the BD swap, you have to perform a complete OP readjustment process (that requires all those special tools - jig, DMM, scope, LPM, test discs, etc.) - unless you swap the OP too, together with "its" BD board.

Bottom line: as Kevin pointed out, it makes much better sense to swap the whole drive, unless your donor has faulty components you need to exclude/replace first.

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only just stumbled on this,if its the owh its held on by one small screw and a little block connector, the 5 series has a ribbon cable, one time i bought a mdm7 off a guy and had a knackered owh,the original owh was good so i fitted it to the drive i bought and all was good,this was between a 940 and 470, though as far as i can make out the owh itself is the same as 480/980 so that should broaden you search, i am sure kevin or guyla will be along to point out if i am wrong,ive done bd board swap before again it was from a knackered 940 mdm7 to save a 440 and all seems well,however in that case again it was from same varient of mdm 7,a used cheap as possible 480 is a good option aswell for the whole unit if comes to that.

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