Sony MDM-X4, Yamaha MD4 and about 15 years

I am conducting an experiment on my equipment that is hopefully to your benefit, but I am not a repair person, and if you blow up your gear while referencing this post, my sincerest condolences will have to suffice.  Use this information at your own risk!

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OK, so the truth is, my absolute favorite recording device ever invented was the Sony MDM-X4.  It was the first somewhat affordable digital device (I paid $899 at a time when I had no business paying $899…but then, isn’t that how ALL the best music gear is acquired?).  So, one day, I worked with a friend named Wayne back in Arizona to bump all the minidisc content to a compact disc.  Then I sold the Sony.  Then I lost the compact disc.  I still have the jewel case for it… it surfaces from time to time just to mock me.

IN 2008
So, in 2008, as a side project, I fired up the crazy bazaar known as e-Bay, and found a Yamaha MD4 for $50.   It was listed in working condition, but it turned out to be flakey – I got it working for a couple sessions, but by the time I decided to pursue a refund, the seller had long since disappeared.  So I set about repairing the thing.  This hasn’t gone so well.

IN 2010
But while I have the unit gutted, I thought…hey, maybe I could share what I have learned…little as it may be! And so it is 2010, and here is what I can tell you about the Yamaha:

  • The two most common issues I have read, to date, are about discs getting stuck in the drive, or generally non-readability of the discs
  • The only way to work on the drive is to take the unit apart.  The good news is, a regular phillips will go a long way on these nice 1990s parts.  The bad news is,  the drive is not easy to access.
  • To access the drive, turn the unit upside down and remove all the screws around the edge (6), and all similar size screws from the bottom (the larger screws anchor the power supply, no need to touch) – there are 8 screws on the bottom (total 14).
    First set of yamaha MD4 screws
  • After removing the 14 bottom screws, the entire base plate should come out without resistance.  If you have resistance, double-check you got all the screws.
  • Next you will need some foam, or towel, and a maybe a pair of needle nose pliers if you are like me and need help fishing screws out (no, I don’t use magnetic screwdrivers).  To access the disk you will need to remove the power supply which is anchored by four larger screws (at the edges, not the four you saw through the bottom – those we don’t have to touch ever), and some smaller screws.  The power supply will lift without resistance, so position the foam or towel (or gym socks) so the power assembly can literally fold back on to the other components (hence the cushion between so nothing gets damaged).
  • Now you will have access to the drive unit.  This is where my memory gets fuzzy because I modified my drive (as you will see), but from here you are free to tinker and I will talk about some of the stuff you might see!
  • There’s a number of ribbon connectors – these are very delicate so be careful.  And you’ll want to make note which way the metal connection of the ribbon is facing when you disconnect them.  To open the connector you pull the two sides with equal pressure towards the ribbon.  Once open (about an 1/8th of an inch), the ribbon will slide out easily.  Sliding it back in sometimes takes a little more finesse…
  • Another thing you will notice is that the MD4 uses a combination of mechanical and electronic switching to determine the state of the drive door. I am not entirely sure why, because I think the mechanical switch combined with the door sensor should have been enough.
  • The reason I took mine apart is because the disc got stuck and after 2 days of off and on fiddling I couldn’t get it free.  I traced it to a set of gears that turn in order to slide a  small metal piece out of position (enabling the door to open…and blocking the door from opening even if you press the mechanical eject button).  So I was able to spin this gear the correct direction and that allowed the door to open.
  • So, what I decided to do was modify my drive.  That way I could access this assembly in a pinch to manually open the drive.  What I did was remove some stuff (yeah… that’s as close as I can get, sorry)…
  • Then I used a twist tie to anchor the drive-open switch so the drive always reports it is closed (the unit won’t function if it thinks the drive is open – go figure).
  • Last I connected the ribbons with the drive on the OUTSIDE of the chassis – this is fairly risky, but I was desperate 🙂
  • After reassembling the chassis, I have full access to the drive.  But my new error now is an ERROR 07 which is a tracking error.
  • The unit, as it turns out, isn’t tracking because of that same gear that controls the electronic latch for the drive.  Because of my removal of parts, I have disturbed the circle of life (which was already broken anyway).  Basically, I have to manually turn the gears one way to open the latch, then when I load a disk I have to spin the gears the other way to close that latch.  This will allow the OW head to make proper contact with the disk surface when the unit is powered on.
  • The above is my work-around for the disc not ejecting properly, but I am left with my original problem… this unit takes about 20 minutes to warm-up and play a disc properly. So, here’s what I am thinking: This unit was built in 1996.  The two failures are both tracing back to gear-related issues (electric drive-latch, tracking mechanism). When was this unit last LUBRICATED?  1996.  That will be the next thing I try.  True, maybe if I had put some silicon on the electronic latch, I wouldn’t need to take the unit apart and modify it at all…but, so be it. EDIT: And, now that it is all lubed up, it still takes 20min to warm up. Fine by me.

That sums up my MD4 experiment.  I will try to get some pictures up, and maybe I will share the outcome of adding some silicone to this poor dried out machine!  In any case, I hope this is useful to either enthusiasts out there, or people like me who have content they are trying to go back and transfer to a more current format!  I see anywhere from 2 – 5 Yamaha/Sony 4-8 track minidisc units on e-Bay for any given week, so I know there are still people using them!!

6 thoughts on “Sony MDM-X4, Yamaha MD4 and about 15 years”

  1. I am having a lot of the same problems that you have listed. Originally I got the recorder from my mother after she got a disc stuck in it and my dad got it out and it appears to have broken the electrical switch that is on the outside of the disc I was wondering if you could send me a pic or two of that the small floating electrical switch is supposed to look like, and the modifications that you did to get yours working. I appreciate it.

    1. Yeah – I keep meaning to put pics up on this, maybe I will this weekend. I have the pictures, just need to scale/crop them. My modification is not a good long-term fix if you are hoping to use the unit a lot.

  2. Dennis Kronenberger

    Oooops! Lost the body of the text that should have been submitted with my last reply!

    I have a Yamana MD4, and searched out your remedies for disc eject problems. Turns out I may not have a problem with the eject feature and would like to leave a scenario for your evaluation:

    When I insert a disc (with audio), all playback functions are good; Play, Pause, Stop, etc. When I attempt to eject the disc the display shows “Disk locked”. I used your procedure for manually driving the latch mechanism and achieved eject. Noting this condition I reinserted the disc and tried to record. The display shows “Write Protect.” Based on the user’s manual, when a disc will not eject, it states to push the “TOC Write” (Stop button) to update the TOC! Well, using that technique in my case is impossible: I can’t eject the disc because the TOC is flagging the eject circuity, and I can’t update the TOC because of the “Write Protect” status! Have you experienced this problem before? Is there a common point in the circuit distribution for “Write Protect” that can be accessed? Is the logic state for Write Protect a high, or low? Short of finding a service manual for this beast these questions may go unanswered. The write protect micro-switches in the drive appear normal. Thank you in advance for your response.


    1. Howdy – I am not an engineer…just a guy with a screwdriver and healthy sense of adventure. Somewhere around resisters and capacitors is where my electrical knowledge ends (transistors are even a stretch). So I have to admit, a chunk of your discourse is write over my head (that was a pun…sorry). I have to ask, as usually write-protect means the write-protect tab on the disc itself has been engaged (that’s the only time I have seen it). Also, I’ve never had a disc “hording” issue until I got this unit… I think it has been possessed by Golem (my preciousssssss!). The odd blend of mechanical and electrical control over the state of the disc makes it more awkward to troubleshoot…almost like the two groups of engineers didn’t want to let the other decide when to eject the disc! Mechanical! Electrical!!

      I did try to put some silicon based lubricant on the gear assembly, but it still takes 30 minutes to warm-up and stop skipping (this unit also introduces audio artifacts while playing back discs…write protected or not!). I’m just doing what I have to in order to move my old tracks to hard-drive, then this MD4 is going to landfill heaven.

  3. Sup Therage3k, I happened across your page. I recently purchased a MD4 off Ebay. I got it yesterday. I knew when I purchased it that it was having issues with recording. Well it does. It plays MDs just fine. I just learned the hard way not to even name tracks on an existing MD. Since I didn’t pay a lot for it, I was willing to crack it open. Last night after only having it for maybe 3 hours, I took the plunge. I had never had one before period… I now can say that all your info is correct, after the fact. I actually got the drive all the way out with the connecting cords intact. I did completely disconnect the power module. Well I found that there was what looked to be a head or something in the wrong position. I repositioned it to no avail. Anyways, at this point If I don’t get another unit to salvage the drive, I’ll just use the mixer and rca ports until I get bored with that setup. After all that, the MD player does still play fine. So if you haven’t sent yours on to the landfill, send it my way. I may be able to use some parts off it. I have already had thoughts of removing a drive from another device in hopes of success. Not likely though. I may be able to use some parts off it. Just an idea… Sorry so long winded… lol


    1. Well, the saddest part is, now that I got this unit limping along, my Tascam US-144 has gone on the fritz. It bombs in the middle of playback… locks up and then USB reports the unit as disconnected. I wanted to use at least somewhat of a decent audio input rather than the integrated sound card on my motherboard (eww!). Not that 60-cycle hum doesn’t bring back fond memories, but a lot of these recordings already have hum…I don’t need twice as much! Anyway, when I am done, if you are still in minidisc mad-scientist mode, I will gladly ship you the unit…you might have to help with shipping, but we can cross that bridge when the time comes.


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