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Sony MDS-JB940 Repair Problems

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M1JWR

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i have a mds jb940 that has a weak laser, well thats what i suspect as it will play some discs and not others, its not disc make spacific, or how the disc is recorded eg sp or mdlp, it just dosent like some discs, i have 1 shop soiled one that i bought 20 years ago new, californication by the chilli peppers, it wont play that it gives c13, the ones it will play, it does each time and the ones it dosent well no cigar every time, i did clean the laser gently and have replaced the belt.

all discs play no problem in the other player which i will get onto, i realise that replacing the laser is not easy, the other is a mds je470, i know they have the same disc drive, after some reading in the two service manuals, i checked the pin outs on both players to see if the bd board connections are compatable, in the service manuals the pin outs do the same exept they are numbered opposite way round,

i would like to swap disc drives as the 940 is far the better machine, and i will experiment with the 470 at a later date, has anybody done this swap or encountered any issues doing so.

regards   john

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you might want to talk to Kevin (kgallen) - he has a LPM (Laser Power Meter) and is very good at the details of electronics. My first inclination would be to see if you can't adjust the laser. He's done the kind of swap you are talking about, but at the time he didn't have the LPM.

Stephen

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Stephen is being over generous with his recommendation!

However yes, both decks use the MDM-7A drive so go right ahead and put the 470 MDM into the JB. Use the drive only. Keep the two ribbon cables and the mounting bushes of the JB in the JB. There might be a chassis flying lead on the 470 drive. If there isn’t one in the JB then just unscrew the lead and leave it off. You don’t need to change any service settings! Just swap the drive and give it a go. 
 

Once you have a working JB then we can put the ‘bad’ drive in the 470 and mess about with the laser if you feel inclined. If it goes all wrong we’ve only lost the ‘cheap’ 470.

There is an exact match of MDM so there should be no electrical issues here. I’ve had success with some slight mismatch. For example a 480 (MDM-7S1A) works in an MDS-E10 (MDM-7SC) but a 440 (MDM-7A) doesn’t. (ETA IN hind sight this might not be true it’s possible I got both types to work in the E10. I have documented this in one of my long rambling threads on here somewhere.)

Buying a cheap donor deck is the easiest way to save a higher end model when the drive is at fault.

Typing on a phone for now (yuk). I’ll check back later (UK time).

 

Kevin

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hi

yes i did try some laser adjustments on the jb it was originally at 10, i tried it 2 steps either way, no change, on the jb there are the two ribbon cables and two what i would call earth straps,

the 470 has only one, the screw hole is there for another, i did not see any flying lead on either, not shure i know what you mean by that, i take it thats these earth straps, they screw onto the drive and clip onto the chassis, are the mounting bushes the rubber parts where the four main screws go.

my minidisc history goes back 20 years when i moved on from tape and bought a new jb930, several years later i sold the 930 and bought a nice 980 for £100, those were the days it seems,

you cant get those for that now, it was for net md at the time, i still have the 980, at around the same time i also bought a mint mzr 909 for £20, also bought heaps of unused discs, around that time 2007'ish it was boom time if you wanted any md releated gear.

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If the JB drive has two earth leads on the MDM then transfer these over to the donor drive. I referred to them as flying lead to avoid the "technical term" earth strap. They are there for audio reasons.

The 4 rubber bushes and the shouldered screws are unique to the chassis design and set the correct height of the drive to the loading slot. So you need to use the rubber bushes and shouldered screws for the JB in the JB.

Kevin

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Hi

i can now report the results of the drive swap

as per kevins recomendation i retained the jb gromets and screws

i am happy to say the 940 is playing all discs, it does now also record from analogue, as in the recent past it only showed up on vu meters and no sound actually recorded, however it did previously record from cd player direct via coaxial input.

however there is a suprise here the 470 with the 940's drive in it also plays all discs, so the 470 still lives !!!

wonder if all that was wrong was slightly iffy connections on ribbon cables into drive itself, we will never know.

cheers guys i have one more job to do before it can be put into front line service.

its possibly typical of a machine thats been out of action for a long time as many will be

hmmm what now to do with the 470, now i know the drive is ok

regards john

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14 minutes ago, M1JWR said:

i am happy to say the 940 is playing all discs, it does now also record from analogue, as in the recent past it only showed up on vu meters and no sound actually recorded, however it did previously record from cd player direct via coaxial input.

sp: There's the clue it' could be some electrical fault (now gone) rather than anything to do with adjustment. Have you checked the power supplies on both machines? There are weird and wonderful strappings on some of the MD deck power supplies to reconfigure the same components to produce 100, 110, 220, if I recall.

 

So the key question is: does the 470 (with its BD-transplanted heart) record from analogue input or not. If yes, then all is happy and well in the garden. If not, then you've found at least one symptom of the failing drive. Kevin, I'm sure, will have comments.

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Great news!

It’s quite possible a ribbon cable connection oxidised over the years and the act of withdrawing and reconnecting them cleans them up sufficiently. So much so that after typing this I’m going upstairs to do just that with my errant 530 because I’m not sure I ever did the same!

On your initial survey it would be interesting if the same subset of discs read and the same set don’t or whether reading was just generally intermittent. It’s great the JB drive is working in the 470. Give it a good soak test. Then check again tomorrow! (Because with my 530 I’ve thought it all working only to find the following day it doesn’t!).

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Glad to hear you've fixed your MDS-JB940 John. And looks like you now have a working spare player too!

I had a bit of a panic the other night when replacing the belt in an MDS-J980 as it wouldn't turn on when I connected everything back up following the belt swap. I removed the drive again and then put everything back and, hey presto, everything was operational again. I can't be sure but I suspect it may have been down to one of the ribbon cables not being seated correctly.

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it was last night when i did the swap so when test the 940 played 4 of the 17 discs i put in that would not previously including the californication one thats shop soiled.

havent tested with the other 13 yet.

includes 2 maxell golds and a sharp disc they played no problem this time, a lot of my discs were recorded 20 years ago from vinyl with the 930 deck i had then in sp

fast foreward to now, i have put it back on, put the sharp disc in and away she went no problem

i will soon test the 470 and do a recording from vinyl and report back

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19 minutes ago, BearBoy said:

Glad to hear you've fixed your MDS-JB940 John. And looks like you now have a working spare player too!

I had a bit of a panic the other night when replacing the belt in an MDS-J980 as it wouldn't turn on when I connected everything back up following the belt swap. I removed the drive again and then put everything back and, hey presto, everything was operational again. I can't be sure but I suspect it may have been down to one of the ribbon cables not being seated correctly.

did it still have a disc inside, ive had that problem before

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On the stuck disc issue I’ve had this lots of times trying to fix various decks (pain of well documented here!). As ever the main thing is not to force. Depending on the drive usually you can get a finger onto one of the gear wheels involved in disc load and rotate it bit by bit with a finger to eject the disc. My experience is with the MDM5 family of drives (520,530 1998-99 type vintage) and the MDM7 family in my E10/E12 and x40/x80 ranges we’ve been talking about more recently. MDM5 can be done in-situ as there isn’t a belt and all the gears are clearly accessible at the rear of the drive. 

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yeah just had a problem with that on the 470, it went into the constant toc writing stage, it would probably do that forever

so off with the mains, there are two, looking from the back broad ish whits slots, when its off give the broader one a wee and i mean wee push first

the stuck md will go towards out for about quarter inch then give the outside one a wee push keep going till disc is all the way out

no harm done as i switched on and put disc back in only difference is the recorded track the toc hasent wrote isent there anymore

it played the other two tracks normally

still must be some crud on that drive connections, somewhere down the line i will give connecting block a smite of switch cleaner or ipa

and see if that helps

dosent help that 530 you have in that respect i suppose

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anyway i will get back to the 470 experiment md player in the near future

i think its just connectivity probably with the 940 drive sitting for years

ive still got a couple of jobs to do to the 940 they will need a soldering iron to sort i am quite compliant with one of those, not on those microbe bits you get nowadays

its ok its got nowt to do with playback or record its just that two of the opticals have had a knock over the years, there is no damage to main pcb

they have been removed prior so i will replace them when replacements arrive, there is 1 in and 1 out affected they are the older type with trianular

locating lugs modern variety have just two lugs, as optical plugs are either rx or tx 1 of each was required.

dont need to remove main board as with back panel off there is plenty of room for the iron.

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57 minutes ago, M1JWR said:

dosent help that 530 you have in that respect i suppose

Fingers crossed the 530 is behaving so far. Just done a bunch of track divides on one of the MDs I dubbed from cassette last week so played/FF and done a number of TOC updates. Read fine in my MD-CD1 where I’ve just titled it up. Sounds like we’ve all had a decent day!

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i have now re installed the 2 missing optical jacks and the rca coaxial jack, tested in and out with cd player and 980 and all is good.

however as i may have said 1 rx optical remained originally, it did not work anyway, i replaced it too, it still dosent work,

ahh well i am not messing with surface mount resistors my soldering capabilities dosent extend to those, i know how to search for faults etc

betcha it will be one of those and not the thru hole cap that is inline, still ini 1 works fine. so that completes that

next, i bought a 930 that apparently has no sound most of the time, out with the transport cleaned laser re inserted ribbons a couple of times

and power connection its a 5d drive, no belts to bother with, re assembled and put in a sp1 disc and away she went, up to press everytime.

wonder if the previous owner tried mdlp discs,as this player would read disc and appear to play as counter will go round so to speak, no sound will be emitted.

if its as simple as that, bargain !! its playing as i write this.

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pleased to hear about your 530, mustve stumbled on a kinda cure for some issues

shame we cant stumble on a cure for the big headlines thats going on just now.

well the 930 is still playing, i checked its life play time etc 10hrs record and 92hrs play

its done nowt, ive recorded a track with it via optical so thats good.

got it on soak test for awhile.

470 next, that will take a bit more as that ex 940 drive aint too heathy, i am sure its got a broken bit in it

and thats not the laser, summat else is not right, found another on fleabay

will see how i get on with that, its possible it may need lasers swapped, not for the faint hearted !!

yet again its not always the laser is it !!!

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4 minutes ago, M1JWR said:

its possible it may need lasers swapped, not for the faint hearted !!

yet again its not always the laser is it !!!

Rather you than me. Having the calibration kit like IOP board and LPM is a must. Plus a decent anti-static workstation setup.

I'm not so convinced the lasers are at fault as much as appears.

Drive swap would always be my port of call unless I was really desperate - say one of my MDM7SC drives went down and I was certain (how?) it was the laser (although I know a MDM7S1A works and I can do without the serial control). Replacement lasers are costly if they can be found. A donor machine costs in easily if you can find the right type and of course a much easier swap!

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yes ive seen replacement lasers on a well known auction site they work out about 35 quid each, wont be interested in any of those, would rather scrap 470, as you say its a low end model, no harm in experimenting, i did not want to buy any more low end decks to fix low end decks, a guy was selling a 7a drive on the well known auction site so i thought why not, he did discribe it as not reading discs, we will see about that, fingers crossed.nowadays i need about 10- pairs of specs to see what i am doing !!

anyway might be lucky , fortune favours the brave eh !

i switched the 930 on today and put a disc in that said sp1 on it, as i have recordings on both modes and usually wrote what mode on the disc, it wouldent play it, then i looked again and it had 124 mins of music on it, put another in that i knew was sp1 and away she went, when the other was in the 930 did exibit the things discribed with a mdlp disc

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and the 940 too, buy a posh one in good nick with issues then buy a basic one that works for not a lot to fix it, then fix the cheepo one if you can

and if its not the actual laser itself you are laughing.

good luck will be required with the 470 !!!

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  • Richard changed the title to Sony MDS-JB940 Repair Problems

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