Minidisc Repairman Q&A #3

David Popovits
Sigma D.O. Electronics
3, Sheinkin str. Tel Aviv, Israel
Tel. 972-3-6290339
Fax. 972-3-6203579

July 2000

These questions from readers on these 1 2 3 4 5 6 7 8 pages followed David's original article about portable MD recorder repair

  1. Followup Suggestion Regarding question no.3 in the 2nd FAQ, I got the following messege: Dear David I have just read your excellent Q&A articles on the site. A suggestion for getting the Aiwa backlight to stay on - use a small external battery pack which connects to the dc input on the MD. Then the MD will think it is powered from the mains and leave the light on permanently. Worth trying before messing around with the electronics anyway. Regards Andy Taylor (Bill Hemphill wrote a similar remark).

  2. Question Hi David! Just reading through your article and returned emails at and it's great! It's good to see that someone is out there willing to offer advice to problem-stricken MD owners! Keep it up David! I am actually one of those 'problem-stricken' MD owners. I own an Aiwa AM-F7 and have had it since July 1998, so it has served me very well for a few years. It is a Japanese import model and because I live in Australia (240V 50Hz), I use a step-down transformer for the supplied adapter (AC-D401). But that's just extra information for you, I don't think the power-supply caused any trouble. The problem is that a month ago, I dropped my MD severly. Severly in that I mean the headphone cable got caught up in my legs and as I stood up from my chair to walk away from my desk, it pulled the cable and my MD went flying off my desk! Literally! It hit the carpetted floor with a big THUD and that's it. I picked it up and there were no visible dents on it, just a scratch. I thought that would be the end of the MD but I found out otherwise! It could still play all my existing MD's! Wasn't I surprised. OK, so it plays... but it cannot record anymore! (although when it's playing and I tap the unit from underneath with a relatively strong force, the unit will stop and read the TOC again!!!) When I try to record, like you said, it actually looks like its recording (sound coming out of the headphone jacks, and the LCD showing it's recording etc...) but when I actually try to listen to the recordings, I hear nothing most of the time although sometimes, I do hear little snippets of the music (like 2 seconds worth) and then nothing. The time gets stuck at where the snippet is (or wherever) and you can hear the MD actively trying to seek something, but amounts to nothing. I try pressing fast-forward and can hear it trying to but the time stays still. The tracks are actually created during the recording process, and I even can still delete tracks with no problems. I've taken the unit apart but cannot actually see anything wrong with it. Even the magnetic record head looks ok... but would I be correct in assuming that the white magnetic record head is to blame? What can I do? You're advice would be very much appreciated! Regards, Robert

    Answer Hi Robert, Sorry for your MD. The recording problem can be related to the small electromagnet encapsulated in plastic as you assumed. I have the feeling that it is not broken, based on the facts you tell me regarding the ability to delete tracks. There are a few possibilities 1. The recording head is not in the right position. 2. The recording head is ok but there is a problem with laser power during recording. In both cases it is not an easy task to deal with. In addition even if you fix those problems you will never know what other problem is hidden due to its falling. You may consider turning it into a player only.

  3. Question Hi, After reading your informative answers on Minidisc repairs at the Minidisc Community site, (, I'm wondering if you have any experience with SHARP bookshelf units, the US domestic model MD-X5 in particular. My unit is in good condition, but I would like it to display japanese "kana" text which I have titled using a Japanese portable recorder. However, all it displays is, for instance, ^kana^ for the japanese word 'kana'. I know that this model is capable of displaying Japanese text (for some reason when in 'titling mode' the japanese text shows up), but I believe there is something hindering it. Do you know how I can access the service mode in this unit, and if so how i can change the settings to display Japanese characters? Thank you -matasho

    Answer Hi Matasho, I usually put the MD's in test mode using soldering iron near the 'system control' chip, as all the MD's I see I need to disassemble as they are broken. Regarding your MD I will try to find you the manual test mode. Truly yours,

  4. Question hi, i've been reading your articles on about repairs, and i've a question about the sharp 722 US model. I bought it about a year ago on the internet, and well it worked fine for about a month, and then it died out by giving me those horrid U-TOC errors on all the blanks i had, i sent it back to one of the sharp approve places becasue it was still udner warranty, then i got it back and it ws working fine for about anothr month mayeb month and a half, well after that it stopped workign agian by giving the U-TOC errors, it's been out of service ever since then now, and i was wondering is there any way i can repair it myself since the warranty ended long ago? also i notice that the screw off to the side where the lever to release the minidisc is missing also, i'm not sure when that happened but ciould that be the problem? and do you think i should jsut go ahead and buy a new MD\ recorder/player such as the 831 from sharp or something? I'm not sure anymore ever since i kinda got ripped off it seems from sharp. Thanks for your help

    Answer Hi Joe I wrote several remarks regarding the UTOC problem in Sharp MD's, my best advice will be to hide the 722 far from your eyes. Buy yourself an MZR37 or even a 831 (seems better then the 7XX series).

  5. Question Thank you for the advice and information you've been giving on the web site, it's a big help. I have a sharp 702 which can no longer play discs. It can record perfectly, but when I try to play anything, it will pause on its own and then continue playing. This problem was very slight at first; it would only pause once or so per disc. I thought it was a disc defect, or just vibration skipping, but pretty soon it became un-listenable. It almost sounds like it is stuttering now. The player is over a year old so it isn't under warranty. Should I try to repair it, or will the record feature continue to work? I do have a portable player (the ST55), so it isn't really necessary that my 702 can play. Thank you for any help you can provide, Owen Williams

    Answer Hi Owen The Sharp MD do not stop surprising us. To help you let me know few details. 1. Do you have a relatively heavy hand while pressing the keys on your 702? 2. In any case, inspect the upper cover of the MD is it bent even a little? 3. Did it fall ? The reason for my questions is based on my guess that the upper cover puts some sort of contact on the recording head, positioned exactly under it. During recording the pressure disappears because the recording head is lowered in order to touch the upper side of the MD. Since the recording head is moving together with the laser unit, pressing it will stop the movement of the laser and the unit will stop playbacking. It is not a severe problem and the repair should not be expensive. (But if I'm not right...) Truly Yours

  6. Question Hi I was reading alot of your responses for minidiscs. I have a sharp 722. I read the response of why it gets "toc error" and "utoc errors". Mine will still record and play but will do it random. Sometimes it wont record or play at all but sometimes it will do 1 or both. When I put a disc in it will usually say "toc errora" but if I keep taking it out and putting it back in it will read the disc fine and play it. I will note that almost all the screws are mssing also. I am in the U.S but all the shops around here will cost at a minimum of 100 dollars just to look at it. Where should I send it? How much does it usually cost with these types of problems with you guys? I can get it new for 199 u.s dollars now, would it be cheaper to buy a new one? Thanks for your time.

    Answer Hi We don't buy new car whenever the ashtray is full. It is not a mater of money, it is the way we behave with our things. I would suggest you will take the MD to a service shop and put all the screws back. (The correct size in evry location). It is not expensive at all. Then clean the laser unit with a cleaning disk. Press "PLAY" and if something is still wrong feel free to email me again. Truly yours

  7. Question I found your repair information on Minidisc players and recorders to be most informative. In particular, I was interested in your comments about the Sony PSU regulation. Because I disliked the way the unit switches to charge mode everytime you press stop, I elected to buy a set of NiMH standard cells and a separate charger for them. Now I only use these cells in the unit (MZR70) and never connect it to the mains at all. I have learned this lesson from laptop computers where I have seen a lot of units fried when the hapless user (a) connects the laptop to its PSU, which is normally ungrounded (b) plugs an external monitor into the VGA port on the laptop. The PSU presents a significant capacitance to ground which is enough to allow destructive currents to flow momentarily from the monitor into the laptop - presto, destroyed machine. This can happen even if the laptop is turned off. I figured that plugging in cables to the minidisc recorder would probably be safest if there was no ground connection, even capacitively through the PSU. Since the terminal voltage on NiMH cells is 1.2V I assume using them would be quite safe,as long as I never plug the PSU in with a NiMH cell installed, and certainly I've had no problems. They also have a much better capacity (1100mA/hr) then the supplied NiCD cell (700mA/hr). I have four of them and just rotate them around as necessary. It will be interesting to see how reliable the Sony unit is, given some of your comments. I will certainly look out for the write protect interlock switch problem and also insert the discs with considerable care. It sounds like I should take the disc out when not using the machine, to avoid the risk of head damage if it is dropped, too. Mind you, I am extremely careful and gentle with precision electronic equipment and treat everything like a delicate watch. Things last longer if you look after them.

    Answer Hi Andrew Your remarks are very interesting, they show good understanding in the electronic gear surrounding us. Regarding laptops connected to external equipment or any other electronic devices connected one to another there is always a risk of importing problems from one to another. When recording (analog) from the computer to the MD the last sees the ground path of the computer through the speaker out output of the sound card, and hence it is exposed to dangerous electrical shocks coming from the computer PSU. I must state that most MD's and Sony above all have some protection devices against those troubles. In any case my suggestion is to pay attention to every connection you are doing. The recording problem mentioned can be avoided using optical link between the MD and the computer. Most expensive computer cards have optocouplers at the i/o lines (for RS232..). We produce a small product that eliminates electrical coupling in audio path. It is based on high quality audio transformers, and can help in many cases not only to save the MD but also to save the user from electrical shock Regarding the MZR70. Charging its bat. outside the unit is a good practice, not possible with most of the MD around, and if possible the solution is very expensive. One of the advantages of the MZR70 is the possibility to work with standard AA rechargeable bat. On the other hand it is better to record using the PSU and not the bat. So it is up to you to decide what kind of risks you want to take. Truly yours,

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