A Repairman's View of
Portable Minidisc Recorders

David Popovits
Sigma D.O. Electronics
Tel Aviv Israel
([email protected])
July, 2000


My remarks are mainly regarding portable recorders made by Sony, Sharp & Aiwa. They are based on our knowledge coming from repairs we make (5 to 10 daily) on these machines. The first part of this paper presents typical problems with MD gear. The second part gives a few tips about how to avoid some of those problems. The last part will try to answer a question about the difficulty of attempting home MD repair.

A MD portable recorder is a very complicated and sophisticated machine. Let's take for example the Sony MZ-R50, which in my opinion is the best portable recorder ever made. The unit is built from some 600 electronic components and circa 150 mechanical parts. They all have to live peacefully inside a small box. We are talking about 3 motors, a laser unit, disc compartment, recording head a couple of status switches, the user interface including keyboard, LCD display, remote control & a few sockets. In addition there is the power management including rechargeable battery, external battery and a power supply unit (PSU). The electronic part is built around a DSP, a system controller, RF amp, microphone pre-amp, headphone amp, A/D, D/A, memory, motor drivers etc. In addition we can find a few flexible multi-conductors connecting between the internal circuits and components. All the above is implemented in a portable recorder. Some manufacturers do it better in some models and some let us suffer. The main point to take into consideration is that the whole machine has to be perfect in order to make it work well.

The problems:

  1. Screws: Each MD has circa 10 screws holding the bottom cover and the upper. The size of the screws are not the same. For instance the front screw (located near the recording LED) on the MZ-R30/R35 is a self-taping special size. Replace it with another type of screw and the whole mechanism will suffer. The screw holding the arm under the cover of the MZ-R55 is a special one. Put another type and the door will not open well. On the Sharp MD-MS7XX and Kenwood there is a screw located near the front of the discarding lever. Replace it with a little bit longer screw and the disc will not get out. On the back of the same machines there is a screw that, if missing, will not let you operate the machine at all.

  2. Recording head: Here we have a real problem. The recording head is a very small electromagnet encapsulated in plastic and attached to a thin and flexible piece of metal. The electric connection to the electromagnet is with a flexible thin conductor. The connection between the electromagnet and the flexible conductor is very sensitive and is likely to break easily. This fragile part has a relatively large pressure on it while recording as it is forced to touch the upper surface of the disc. Also it may break when the MD falls or if vibrated. When this part is broken recording is impossible. Although the machine may seem to record and you can monitor the sound while trying to record, actually it does not record. The bad news is that this situation is very expensive to fix. As for Sony they do not sell or replace the recording head only but the whole laser unit, which is very expensive. This recording head problem is found largely with Sony recorders.

  3. Power supply: In my experience this is the biggest killer of MD's. To be more accurate, my statement is true when not using the correct PSU. Let's say you live in Australia and buy an MZ-R55 with a 110V type PSU. You connect it to a step-down transformer as you are doing with other 110v equipment. After a few days the machine dies completely. If you are lucky it will live longer. The sensitivity to PSU is mainly with new Sony models (MZR55/70/90/91) all working with 3V. The situation is better with 6V models like MZR30/35/50, and recorders made by Sharp and Aiwa. The Sony PSU's supplied are not regulated, they assume only small fluctuations in mains power. In addition, the safety margin of the components meeting the PSU inside the MD is very small.

  4. External Jacks: Each recorder has between 3 to 5 jacks. One is the PSU jack. Try to connect a different plug and you will probably break the jack or the PCB or both. The white input jack on Sony and Aiwa MD's serve as analog/optical input. The jack has in addition a few extra functions. It is an expensive jack that we tend to break when using cheap cables. Inside the jack there is relatively high pressure on the plug. If the plug is a cheap or bad type you may find that when pulling it out the tip remains inside. To extract it is almost impossible. As for electronic problems, connecting an analog output from a computer while it is made through the speaker output of the sound card to the sensitive MIC input while the volume of the computer is high can destroy the MD's mic pre-amp. Connecting the same signal by mistake to the MD line or headphone output can damage the line or headphone amp.

  5. Heat and moisture: MD equipment doesn't like it. Heat can stop the machine and moisture meeting dirt will put severe force on the mechanics.

  6. Pressure: Sony (new models) Aiwa and Sharp have their buttons mounted on top of the machine. Pressing too hard on the buttons in general (and even when being very gentle), one can find that after a while the upper cover is bent. This puts pressure on the recording mechanism and can cause many problems. Under the cover of AIWA MD units there are many screws. Pressing the buttons can loosen the screws and oops! they fall directly on the laser unit. Last week I repaired a AM-F75 having the ``DISC ERROR'' message on the display. The unit was 4 months old. I found a 2mm screw inside the laser unit, which moved the lens from its position. The owner was lucky as it started working fine after taking the screw out. As for pressure on other parts of the MD. Putting too much pressure while holding the MD or a bent cover can put extra force and pressure on moving parts inside the MD. You will hear funny and sad noises as the motors are trying to pass the obstacles.

  7. Right disc: Some discs will cause us problems. Using types that have low reflectivity will put extra stress on the laser unit. A too flexible housing on a disc can bend the MD, some non-metal shutters on discs tend to bend, mainly in hot regions, destroying the loading mechanism.

  8. New designs of electronics for MD makes repairs expensive: The DSP and control IC's in new Sony recorders e.g. MZ-R90/91 cannot be removed from the board due to a packaging design in which the pins are mounted under the chips and cannot be accessed for de-soldering. When these chips malfunction they are impossible to replace and the whole electronic board must be replaced at considerable expense.

Tips - how to avoid some problems related to MD gear

  1. Buy the right MD. If possible, buy a portable player. Those tend to have less problems than recorders. Do your recordings on a MD deck, It's easier. If you cannot have 2 MD's as stated above buy a recorder that is known to be strong as possible. Try those having hard metal covers (MZ-R90/50) and those that are not known to have recording problems. You may refer to opinions brought by members of the MD Community Page.

  2. Protect MD screws from falling. Apply transparent nail polish over the heads of the screws to avoid their falling out.

  3. Protect the recording mechanism. As much as possible avoid dropping and vibrating the recorders. If you must run with a MD use a player instead of a recorder. Place the disc inside the unit while it is in parallel with the cover to avoid touching the sensitive recording head. Many recording heads (mainly in AIWA MD's) get damaged because of bad insertion of the disc. If you want to clean the optical units do it with a cleaning disc, otherwise the cleaning must be done with removed cover, so as to avoid damaging the recording head. Do not use an air compressor to clean the inside of the MD. It may cause damage to the recording head and other sensitive parts.

  4. Use high quality cables for recording and playback. One reason is that such a wonderful machine deserves good cables, but to be more practical bad and cheap cables can deform the jacks and can cause unexpected short circuits etc. I don't ask you to buy those multi-$ cables, something in the middle will do the job. As all the cables connected to the MD have 3.5mm (1/8'') plug, you may mistakenly connect the wrong cable to a jack. To avoid this, mark the plugs with a tape having the same color as the jack it is intended to be connected to.

  5. Use the correct PSU. For units having an original 110V adapter, almost no problems are to be expected when used in the United States and North America. In other countries use an original adapter with the mains input rating the same as the mains of that country. For e.g. UK it should be 240V, etc. You may use a step-down transformer for 220 mains voltage countries if you have a 110V original PSU only if the mains voltage in your country is known to be very stable. Pay attention because some units come from Japan, where the mains voltage is 100V. For new models of SONY recorders working on 3V, even if the mains voltage in your country is stable, a 220/110V transformer will cause problems. You will have to use a 220/100V step-down transformer. 10% difference in the input voltage (110/100) will cause 10% difference in the output voltage and the MD's hate this situation.

    How about countries with unstable mains voltage? (Some parts of India and other countries). For those even an original Sony power adapter with the right input voltage can cause damages. 60% of all new Sony MD's we are repairing (MZ-R55/70/90/91) came to our desk due to PSU problems. We solved this problem by developing a special line of PSU's based on our knowledge of the electronics found inside the MD. They are highly regulated and stabilized in output and self adapted to any voltage between 100-250V. It means one can travel with this MD all over the world, even to India and face no problem due to electrical system differences. We have PSU's for 1.5V, 3V, 4.5V (for Sony & Aiwa MD's), 5V (for all Sharp MD's), 6V (for MD's & Sony DAT), 9V, 10.5V (MZ-1), 12V etc. None of these PSUs we make has ever damaged a MD and they live well for many years without complaint from our clients.

  6. Maintenance: Do not lubricate mechanical parts unless you are well trained in fixing MD's. Only special lubricants will do the work without making things worse. In extreme cases mechanical parts will refuse to move due to dirt build-up around lubricated parts. Clean the outer covers with a soft cloth. Check for dirt and clean all jacks with a dry soft cloth. Avoid letting sand enter the machine. If you go with the MD to the beach, hold it inside a well-protected bag. After using the MD do not leave it connected to the mains unless you need to charge the battery. A sharp spike over the mains will kill your MD and if you have an MZ-R55 you may end up with the famous self-activating record problem.

Replacement of an optical block assembly by a normal person: Yes or no.

To answer Eric's question:
``It might also be interesting to hear your assessment of how easily a normal person could undertake something as serious as replacement of an optical block assembly.''
I will tell a small story. A few years ago one of our clients brought us a mysterious machine called the MZ-2P. He told us that the display shows DISC ERROR and asked us to repair it. Among other things we do in electronics we repair all kinds of electronic equipment. As for myself I admit I know to repair airplanes as well as video cameras and complicated computers and industrial equipment. I took the MZ-2P into my hands and opened its covers, trying to start repairing it. It was the first time I held an MD unit in my hands. After 2 minutes the MZ-2P stopped working completely. No sign of life, no messages on the display, nada. It took me 7 days to bring it back to the original DISC ERROR problem and another long time to fix the problem. It was a very shocking experience. Then I decided to take things seriously and I learned the material very well, so today I am fixing 5 to 10 machines daily.

If one is about to fix his MD unit he should be very good in electronics and mechanics. Second step - he must have the service manual for the unit. Some new MD's cannot even be opened and still remain undamaged unless you follow the steps outlined in the service manual. In addition you must use high quality tools: precise screwdrivers, excellent tweezers, anti static soldering iron, etc. You must wear an antistatic wrist-strap in order not to damage the components and especially the laser unit. It is a good practice to wear rubber gloves so as to keep the internal parts as clean as possible. If you don't have the service manual and still want to continue, write down the location of each screw and use a small magnet to hold the screws and other small metallic parts. Remove the bottom cover and look inside. Are you impressed? I'm always very impressed. Now I would suggest that you close it back up and do not attempt to fix it by yourself. If you are well experienced with repairing MD's you probably don't need my advice on how to repair them and if you are not, my best advice to you is to close it and do not attempt to make things worse.


I asked David for clarification about the number of machines he was repairing, 10 a day sounded like an extraordinary quantity in a small country where MD is expensive and not so popular. He responded as follows.

Let me explain to you the situation with MD in Israel. During the last 3 years it has become very popular especially among teenagers.

The problem is the high prices of MDs in my country. This situation is due to almost 100% customs and 17% vat. Add the profit of the importer/distributor/retailer and you get an MZ-R55 for $500, MZ-R91 for $600 etc. Ispar Ltd, the representative of Sony in Israel, is the only representative that sells Sony MDs. The Aiwa and Sharp importers do not import MD gear at all, neither do they service those machines. Of course there are shops not related to the importers that import MDs from dealers in Japan and other countries. I would say that most MDs in Israel are bought outside of Israel, mainly in the US and Far East by people visiting those countries, or at a tax-free shop at our international Airport when one travels. You may buy at those shops without paying customs for MDs priced no more than $200. These days they sell Sharp model MD-MT15.

Regarding repairs the situation is more complicated. Sony in Israel recognizes guarantees for MDs bought in their shops in Israel only. So even if you have an international guarantee from Sony they will still charge you fully. Also there is a laboratory for MDs bought at the free tax shop in the airport. All the others have to look for service and pay for it. At Sony you pay very much for every repair. Not everybody is ready to pay those high prices, and on the other hand I believe my shop is almost the only one that is ready and capable of repairing all MDs. It is not easy, as it is difficult for me to get all the parts I need, but as we give this matter our greatest attention we manage to repair almost all the MDs brought to us. Yesterday, for the first time, I repaired a JVC MD unit. It is a very nice machine and looks like Palm Pilot, but is rather heavy. It came to me completely dead due to wrong PSU. In addition there was no sound coming from the earphone socket, and it was not recording. I do not have any documentation or service manual for this MD unit but I fixed it completely. A transistor in the power circuit was damaged. At the amp output 2 "muting" transistors where exploded completely and I had to guess what the original ones were. The recording head was bent completely but somehow not broken so I could fix it, and now I have another happy client.

As for the numbers. I respect your question and your effort to have real facts in the texts placed at the site you are managing. To be more specific, I hold daily more than 10 MD units. Some of them have very small problems, which I repair at the counter (missing screws, etc). Full repairs I do on 70 - 100 MDs monthly. Regarding pictures. In the future I will try to send you more interesting pictures than simply a picture of myself, i.e. pictures of the tools I'm working with, special tools I've made myself, the measuring equipment etc.

Truly yours,
David Popovits

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