Hi, i was hoping you guys/gals could help me with repairing my old minidisc players. I actually have two cosmetically nice players in the MZ-1 and MZ-2P. Sorry for the long post but I wanted to provide some info in hopes that someone could share their similar experience or point me in the right direction. Thank you so much in advance for your help. ISSUE #1 The MZ-1 has always worked perfectly, but after putting it away a year or two ago and not using it since, now all of a sudden some of the face buttons have stopped working - the numbers/letters, the pause button, and the skip track buttons. Strangely enough, the other buttons still work, including ENTER/REPEAT, PLAY, STOP, and Search (FF/RW) buttons. ISSUE #2 My next issue is also with the MZ-1. It plays discs perfectly when using batteries (2x 18650 lithiums with custom adapter), but when I plug it in with the official 10.5v power adapter (AC-MZ1) it won't read any discs. It just immediately says "DISC ERROR" for any disc I put in (prerecorded or recordable). I'm actually not sure when this issue started because I only ever used it with batteries before I bought the MZ-2P a couple years ago. At that time I put the MZ-1 away. This really isn't a big deal because I can keep using it with batteries (if I could get those face buttons working). ISSUE #3 Finally, the issue with my MZ-2P is that it has trouble playing recordable discs. It will read most of my recordable discs and will play many of the tracks just fine, but it gets "hung up" often. However, it reads and plays prerecorded discs perfectly though. From my research, this seems to be a pretty common issue and probably has something to do with the laser and/or the power of the laser. I did try adjusting the CD read power by turning the RV519 potentiometer. Although, I don't have an oscilloscope so I couldn't do it properly as per instructions on page 31 of the manual. QUESTIONS At this point I'd really just be happy to get either one of these units in working condition. Do you think it's worth trying to remove the the laser (optical pickup) from the MZ-1 and putting it in the MZ-2P? The MZ-1 uses optical pickup KMS-130B. The cover of the MZ-2P service manual (and other places online) says it uses KMS-130A, but then on page 65 of the service manual it lists KMS-130B. Hmm. I wonder if they're interchangeable? I'm not sure if I can just do a mechanical swap and see what happens or if it's imperative to do the electrical adjustments steps afterwards(?) with an oscilloscope as per the service manual. Or perhaps the issue with the MZ-2P is not the laser and instead it needs some capacitors replaced? Regarding the face buttons on the MZ-1, could that be a fuse or something? I'm confused as to how some of the buttons are working and others are not. SUMMARY Has anyone run into these same issues and found a solution? I'm clearly over my head here, and I'm getting close to just taking them to a repair service, but I would love to figure out these issues myself. While I don't have much knowledge in electrical engineering, I am handy with a soldering iron, I have the service manuals, and I'm very eager and willing to learn. I hope someone can help point me in the right direction or share their experience with fixing these issues. Of course, I have searched high and low on the internet and youtube, but I haven't had much luck finding help. Thanks so much.
The MZ-1 is a pretty complex device and while I'm not familiar with it I want to share some thoughts regarding your issues: 1. The reading "pressed" discs and not reading recorded ones is an indication the laser is on its way out. But given the vague description I cannot tell if that is your problem. However if that's the case, adjusting the power is the worst thing you can do because it will shorten the lifespan of the laser diode dramatically and will only be a temporary fix. You don't need an oscilloscope to adjust the power, that adjustment is done so the current draw is a specific amount usually written on the optical pick-up block. Current needs to be in a specific interval, you should not increase it. It's one of the adjustments that should never be touched. You say "hung up", what do you mean exactly by that, it freezes and keeps repeating the same 2-3 second passage ? As for capacitors causing such an issue, I would look elsewhere. First you need to clarify what the issue is exactly, cause I'm confused. 2. Face buttons stopped working: this can have many causes including dirty contacts (although it would be hard to believe all are dirty suddenly), a missing ground, a missing power supply on the pull-up resistors or even increased contact resistance if the buttons work by reading an analog voltage off a divider ladder. I don't know how they are implemented in this device (could look it up if you provide a service manual), so cannot say what the fix is. And no, there's no fuse that can cause this problem. As for how the buttons are working, there are 2 main possibilities: - they are pulled to a power supply via pull-up resistors and they connect to ground when pressed. The microcontroller reads the logical level directly and triggers an interrupt in the CPU. - there is a resistor ladder which creates a different analog voltage when a particular button is pressed. The ADC of microcontroller reads the analog voltage and triggers a specific interrupt. 3. About the MZ-1 power supply, first of all check the power supply. Does it have the correct voltage ? Does it have excess ripple ? Unfortunately you need an oscilloscope to check the ripple. Open the supply and check if there are any bulged capacitors inside it. However, I have an impression the MZ-1 operates on a lower voltage internally and there either a linear regulator(s) or a buck converter(s) that create the lower voltage and that's most likely what's causing the problem. But again, without a service manual, I can't get you the details. Repair can be as simple as a bad capacitor or can be more complex. The KMS-130A and KMS130B may be interchangable. Question is if they are physically identical and if the flex cables have the same pinout. You can check this in the service manuals.
Hi, thanks so much for the reply. It was helpful, and I actually learned a lot reading it! Good to know about the laser power. I tried to put it back at the exact position it was originally. I would love to be sure about that. The service manual reads: "Adjust RV519 so that the RF amplitude (at TP102) is 1.0V +/- 0.1." Is this something I can do with a multimeter and/or oscilloscope app on my computer? That's the extent of my testing equipment, unfortunately. By "hung up" I mean it will get stuck and not be able to play a track. For example, on one of my recorded discs it will play all the way through until track 15. When it gets to track 15, on the display, where it typically shows the track time, it will show "00m00s" for around 10-20 seconds without playing any music, then it will flash the word "access". After 10-15 seconds and what sounds like the laser moving back and forth inside the machine, it will play maybe a second or two of the song. Then it will stop again, flash "access" for a few more seconds, and then usually skip ahead a few seconds, sometimes play a glitchy sound along with another couple seconds of the song, etc. Also in this example, it won't play any of track 16, but skipping to track 17, it will play that right away. It's very inconsistent. Some tracks play fine. Others simply won't play, and others will have skips/glitches/freezes ranging from a tiny blip to the more severe scenario I just described. I just checked the voltage of the power supply. It's the official Sony one, rated at 10.5V. The multimeter is reading 18 volts!! Ouch. That definitely explains why the MZ-1 won't work with the adapter, and I'm assuming it's why the face buttons stopped working. I guess it fried something. Hopefully I can fix it. I'll look into the two possibilities you listed. It's a little over my head, but it's a good nudge in the right direction for me to start learning, so I appreciate it. Regarding the KMS-130A and KMS130B optical pickups, I'll look into the pin-outs before I try anything. Thanks for the heads up. Thank you again for the reply. I've attached the service manuals if you or anyone else is interested in taking a look.
Glad my post was helpful ! I did find the laser read power adjustment (there is also a separate write power one), don't know what to say. It's possible that the manual assumes the laser is new and at that point I would do the adjustment, but on an old worn one it's debatable. Unfortunately you do need an oscilloscope for that, won't work with a PC app as you need high sampling frequency not what a sound card can do. And then question is if increasing the laser power does improve the situation or not, cause from what you stated it doesn't make any difference. Is the hang up consistent on all written discs ? Does it hang up in a similar position near the end of the disc ? There is more to investigate before drawing any conclusions, despite it does look like a laser power issue. The power supply reading 18V that's perfectly normal as it's a linear non-regulated power supply which will output a siginificantly higher voltage with no load. It's why I recommend adding a regulator to these supplies, but the supply is not your problem. If you measure the voltage with a load, like connected to the device and device on, you will see a much lower voltage. This needs a more careful look at the internal supplies and how they work. Will take a look at the service manual in more detail later on. The buttons are using a resistor divider ladder, so increased contact reasistance can cause them not to work. If the voltages are not within a certain interval, the microcontroller won't register a button press or will work erratically. It's also still possible that you have a missing ground or power supply on the buttons circuit, so broken traces (especially on flex cables) are to be checked for. The KMS-130A and 130B look to be identical and I think it's worth trying to interchange them. It's possible the the B version is just an updated version and they're identical. It's also possible that the operating currents of the lasers are different (in writing mode), this can be checked on the sticker of each laser. The MZ-1 has a section in the manual about that, while the MZ-2P seems not to have it. While there is variation in the laser current between units, if one is 50mA and one is 100mA for example, they're not interchangable.
Well, the MZ-2P is a player only. It has no recording function like the MZ-1 does. Do you think think the MZ-1 laser could still work in the MZ-2P?
Ah, didn't realise the MZ-2P is a player only. That explains why there is no writing current adjustment. I don't know what to say, please post some pictures with the sticker on the optical pick-up. Recording is done magnetically on MD, the laser just heats up the disc up to the Curie point, but doesn't actually write any data. It is possible the pick-up blocks are still the same and the MZ-2P misses only some circuits and the magnetic record head. It's also possible that the MZ-1 one has a more powerful laser diode inside that can be operated in recording mode, while the MZ-2P has a weaker one for playback only. If this is the case, you could swap the MZ-1 one to the MZ-2P, but not the other way around. Put some pictures with stickers, maybe those reveal more info.
