BearBoy Posted March 12, 2020 Report Share Posted March 12, 2020 I'm not having much luck with my MiniDisc decks at the moment. My MDS-JB940 and my main MDS-JB980 are both having eject issues (I think the belts have gone). I've ordered a replacement belt so hope to get one of those fixed this week and, assuming it's successful, will order a belt for the other. Whilst those two machines were out of operation, I put my spare MDS-JB980 into my office system but I am having some issues with it. I bought the device a few years back and, after some brief testing, it has sat in its box in a spare bedroom. It seems to play MDs without any issues but I am having issues with recording. I have carried out two types of test today using three devices (the faulty MDS-JB980, an MDS-JE500 and an MZ-N910) with these results: Test One Insert blank disc into MDS-JB980 Record CD via optical input – tracks show but do not playback (mechanism whirring but never displays 0:00 and starts playing) Eject MD – TOC writing Re-insert MD – shows as blank disc Insert recorded disc into MZ-N910 – shows as blank disc Insert recorded disc into MDS-JE500 – shows as blank disc Test Two Insert blank disc into MDS-JE500 Record CD via optical input – playback works fine Eject MD - TOC writing Re-insert MD – playback works fine Insert recorded disc into MZ-N910 – playback works fine Insert recorded disc into MDS-JB980 – playback works fine Enter track name using MDS-JB980 Eject MD – TOC writing Re-insert recorded disc – shows as blank disc in all three devices Yesterday it seemed slightly better at recording and some tracks (although never the first recorded track) would play back on the MDS-JB980 and the other devices but then the "blank disc" issue would occur after trying to name tracks or re-record the first track that wouldn't play back. The first disc I had the issues with was a brand new sealed Sony MDW80T. I initially wondered whether it might be a disc issue but have had the same results with a different disc (and the discs work fine when recorded on using the MDS-JE500) so I think it must be the deck). Any ideas as to what the issue might be and whether there is anything I could do to fix it? Quote Link to comment Share on other sites More sharing options...
kgallen Posted March 12, 2020 Report Share Posted March 12, 2020 Sounds like an overwrite head (OWH) issue. The "making a disc blank" issue in the 980 is probably because the laser is still working during recording and heating the bit position to the Curie point, but the OWH is not providing the polarising magnetic field which orients the bit to encode a digital "1" or "0". This is the "magneto" bit of "magneto-optical" (MO) drives, minidisc being a classic example. If you have a DVM, first step with the machine OFF and the lid off is to do a continuity check on the overwrite head. Poke me if you need more detail. Second step is to find another machine with the same drive and do a transplant! The drive in a 980 is an MDM-7S1A and these are (only) found in the 480, 780 and 980. You might be able to find a cheap 480 on eBay. This is not so cheap (£50), but "cosmetic damage" is what to look out for as a donor machine as long as it's otherwise listed as working. Then strip it for parts like the drive. https://www.ebay.co.uk/itm/Sony-MDS-JE480-MiniDisc-Player-Very-Heavy-Cosmetic-Damage/324036319093?hash=item4b7211d775:g:tL8AAOSwljFeFf9g Quote Link to comment Share on other sites More sharing options...
BearBoy Posted March 12, 2020 Author Report Share Posted March 12, 2020 Many thanks for the reply Kgallen. I've got one of THESE if that's what you mean by a DVM? Sorry, I am far from being an electronics expert. If it is, I would be very grateful if you could give me some instructions as to what to check with it. Good to know I could use an MDS-JE480 as a donor machine. They're generally a lot cheaper than a replacement MDS-JB980 and my faulty machine is cosmetically immaculate. Is a drive swap a complex task? Quote Link to comment Share on other sites More sharing options...
kgallen Posted March 12, 2020 Report Share Posted March 12, 2020 14 minutes ago, BearBoy said: Good to know I could use an MDS-JE480 as a donor machine. They're generally a lot cheaper than a replacement MDS-JB980 and my faulty machine is cosmetically immaculate. Is a drive swap a complex task? Exactly, for the reasons you say - cheap and perfect donor into a nicer machine. Easy-peasy to swap the drive. Lid off, 4 mounting screws, 2 ribbon cables, maybe a chassis lead. Pop the new one in, reverse the above. Happy days. Kevin ps I know the 980 is a little "fancier" (and I don't have one) so the drive might be embedded in the chassis assembly more, but all of my machines are as easy as above. pps I've just downloaded the Service Manual, and from the assembly diagram it does indeed still look as simple as the above. Some machines I think have sliding trays (not sure which models) and these might be quite different. Quote Link to comment Share on other sites More sharing options...
kgallen Posted March 12, 2020 Report Share Posted March 12, 2020 25 minutes ago, BearBoy said: I've got one of THESE if that's what you mean by a DVM? Sorry, I am far from being an electronics expert. If it is, I would be very grateful if you could give me some instructions as to what to check with it. Yep, that's one of 'em. Do you want to go down this route? If we find the OWH is open circuit, for all practical purposes we swap the drive. If the OWH isn't open circuit, then there is a fault in the drive circuit. For all practical purposes we swap the drive. If one of my machines had this problem, I'd probably try and diagnose it more, but only for simple issues like there was a lose or broken wire, or the lead wasn't plugged into the PCB. After that, I'd swap the drive. Kevin This is a picture of the overwrite head assembly. It's on the top of the drive. The OWH head itself is a tiny patch on the underside of the end. There are two metal strips that run the length of this moving assembly. Checking continuity (with the unit OFF!!!) between these two metal strips would determine if the OWH was open circuit. But there probably is no real benefit of going there! There will be two black wires that come out lower down, terminated in a 2-pin connector. Check this is mated ok with the other part which is soldered to the controller PCB. You can do all of this with just the lid off, no need to remove the drive itself. The drive might have a metal cover over the rear of the drive - they do that on the expensive machines, but leave it off on the cheap ones! There are 4 screws to remove the cover but this east easier with the drive out. NEVER have the machine PLUGGED IN with the lid off. The laser is invisible and can blind you instantly. Also there are exposed parts a full mains voltage even when the machine is "off". Quote Link to comment Share on other sites More sharing options...
BearBoy Posted March 12, 2020 Author Report Share Posted March 12, 2020 Thanks Kevin - that's really helpful. I might pop the lid off and see if there is anything glaringly obvious but it sounds like I just need to pick up a donor deck from eBay. Quote Link to comment Share on other sites More sharing options...
kgallen Posted March 12, 2020 Report Share Posted March 12, 2020 Pop the lid off and let us know how you get on. Meanwhile keep an eye out for a 480. Quote Link to comment Share on other sites More sharing options...
BearBoy Posted March 12, 2020 Author Report Share Posted March 12, 2020 Argh! So I went ahead and tried to replace the eject mechanism belt in my "good" MDS-JB980. Followed the instructions elsewhere on this forum. Getting the belt on was a bit fiddly but I took it slowly and was very careful. Put everything back together, turned on at the mains and the small red standby light came on above the power switch but the deck won't turn on. Have tried the button and via the remote and nothing happens. I have checked the two ribbon cables and they both appear to be undamaged and seated correctly and I reconnected the two earth leads back to their original locations. Help! Anyone got any ideas about what might have gone wrong? Quote Link to comment Share on other sites More sharing options...
BearBoy Posted March 12, 2020 Author Report Share Posted March 12, 2020 Okay, panic over. No idea what I'd done but I took the drive mechanism out again to see if I could see any damage anywhere. Everything looked okay so I put it all back together again and this time it turned on. When I reconnected the power the first time there was a faint click when the standby light came on. Following the reassembly there were two. I must have done something wrong but no idea what. Just glad it appears to be alive again. And the eject mechanism works fine now. Quote Link to comment Share on other sites More sharing options...
kgallen Posted March 12, 2020 Report Share Posted March 12, 2020 Well done! Sorry other than a bad connection I couldn’t think what could cause this. Badly seated ribbon cable would have been my only suggestion. Glad you’re sorted now and the eject works. Thanks for letting us know! Kevin Quote Link to comment Share on other sites More sharing options...
BearBoy Posted March 12, 2020 Author Report Share Posted March 12, 2020 So now I have two working MDS-JB980s. After sorting the belt issue on my first one I thought I just take a look inside the other and see if there was anything obvious that might be causing the blank disc issue. I had noticed two white wires soldered onto the over write head when I was changing the belt on my first machine and was wondering, probably somewhat optimistically, that it might be as simple as one of these having become disconnected. It actually turned out to be something even more glaring. I am not sure if this is common to other Sony MD decks but the MDS-JB980 has a rectangular metal plate stuck (literally - it is held on with a combination of double side sticky tape and glue) to the underside of the case lid. I know this because when this machine arrived it made an alarming metallic clunking sound when I removed it from its box. I was really worried at the time that it had got seriously damaged in transit but it transpired that this plate had fallen off and, luckily, had not caused any damage to the inside of the deck. At the time I stuck it back on with some insulation tape and then, after making sure the deck worked, packed it away as a spare. When I opened it up today I saw that the plate had fallen off again and was sat resting on top of the drive mechanism - quite probably resting on the top of the over write head. The insulation tape I had used to stick in back in place previously had re-adhered to the back of the chassis and so the plate itself wasn't moving around and making the metallic clunking sound I had heard when it first arrived. I removed the plate and ran a few tests with the lid off (just titling my test disc and then ejecting to get the TOC writing process going) and when I reinserted the disc I didn't get a "blank disc" message and the disc was playable. I relocated the deck back into my office system and have made some successful test recordings. Just wondering if I need to put the metal plate back in place? Not really sure what it does. Maybe some sort of shielding? All in all a successful evening. I've ordered a replacement belt for my MDS-JB940 now so will tackle that next. Quote Link to comment Share on other sites More sharing options...
BearBoy Posted March 12, 2020 Author Report Share Posted March 12, 2020 49 minutes ago, kgallen said: Well done! Sorry other than a bad connection I couldn’t think what could cause this. Badly seated ribbon cable would have been my only suggestion. Glad you’re sorted now and the eject works. Thanks for letting us know! Kevin Thanks Kevin and thanks again for your advice. I think it may well have been one of the ribbon cables (not really sure what else it might have been) but I did try re-seating them before I took the whole mechanism back out and it didn't make any difference. Anyhow, it's working now. I think I'll still keep my eye open for an MDS-JE480 to squirrel away as a donor deck so thanks for the suggestion. There's no rush now though so I can be patient and try to get one at a good price. Quote Link to comment Share on other sites More sharing options...
kgallen Posted March 12, 2020 Report Share Posted March 12, 2020 Great story, so glad you have both of your machines working now! Also I think you’ve found your way around your machines a bit so I think you’ve learned a lot. Same for me - 18 months ago I didn’t know an MDM from a... mmmm Malteser! Kevin Quote Link to comment Share on other sites More sharing options...
kgallen Posted March 12, 2020 Report Share Posted March 12, 2020 7 minutes ago, BearBoy said: I think I'll keep my eye open for an MDS-JE480 though to squirrel away as a donor deck so thanks for the suggestion. There's no rush now though so I can be patient and try to get one at a good price. Absolutely! I bought my 480 for £9.99 as a ‘broken’ donor deck, but it just needed a belt, so it works now too... And actually it’s my only Type-S deck! Quote Link to comment Share on other sites More sharing options...
BearBoy Posted March 12, 2020 Author Report Share Posted March 12, 2020 £9.99? Wow, that it is a bargain. Very much doubt I will be able to find one that cheap but I'll see what turns up. Quote Link to comment Share on other sites More sharing options...
kgallen Posted March 12, 2020 Report Share Posted March 12, 2020 It was only a few months back. Just prior to the Techmoan MD revival I think! :-D Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.