The Cause of MD Reliability Problems

Shawn Lin ([email protected])

As we probably all know, there is a common problem with Sony MD players. The optical block (laser assembly) often just goes bad. Players skip or fail, returning "Disk Err" messages. Recorders can scramble an unprotected MD. These problems have been reported in nearly all models except for the MZ-1 and the MDS-JE500/JE510/JE700/JA30ES and JA50ES. The MZ-R50 is too new to know its reliability record, but its optical block has been redesigned since the previous model.

I now think I know just WHY the optical block goes bad, and it is not because of a weak laser. It is, IMO, due to cost-cutting on Sony's part.

I received a broken MZ-E3 today, which had been diagnosed as requiring a new optical block assembly. Indeed, it was so severe it would not even play *prerecorded* MD's unless it's sitting on its side or upside-down. Since I had nothing to lose (it needed a new optical block anyway), I took the MD player completely apart. I pressed the safety switches and watched the behavior of the laser. There is a visible red component to the mostly IR laser beam, so I was able to see it through the lens. As the lens focused up and down, I could see the light source shifting towards the side of the lens. This would cause the beam to bend at a slight angle causing the resulting reflected beam to be less than ideal. The lens also shook and trembled a tiny bit while focusing. I wondered why it did this, so I took the top cover off the optical block and noticed something...

The only thing suspending the lens, is a cheap nylon spring bracket!!! I was surprised, because I've seen inside optical blocks before, and they are usually suspended by metal leaf-spring type things. Apparently, what happens is that the nylon spring's joints get worn out and loosened. This reduces tracking and focusing accuracy, so recordable MD's become more difficult to read because they require much tighter tolerances (they're less reflective). Prerecorded MD's usually play fine because they are much more reflective and permit a bit more tolerance to inaccuracy. When the MD player is turned sideways or upside-down, the force of gravity no longer affects the weakened, saggy nylon spring.

The reason the nylon spring becomes weak is because an MD player always has to focus and track. The nylon bracket has "joints" to allow movement (simply a very thin part of the bracket that is creased). Over time, these creases just wear out and become loose. In the case of the 'E3 I have, they were so loose that I thought it wouldn't be too long before they broke.

This fully explains why many MD players work fine sideways or upside-down, indicating sufficient laser power. The weakened spring can also sometimes be compensated for by recalibration, but this may not fix the problem, depending on how weak the nylon spring has become.

On my MZ-E3, I was able to fudge a repair on the optical block. There is a small membrane-type flat cable on the bottom of the optical block that connects to the focus/tracking coils. I noticed that when it is pulled tight, the lens flops around a lot less. So I affixed a tiny piece of adhesive tape to the membrane cable, pulled it so it had less slack, and stuck the ends of the tape onto the optical block to keep it in place. Now, this MZ-E3 will play prerecorded and recordable MD's just fine in any position.

Next time I take my MDX-400 apart, I'll see if I can fix it in a similar fashion (as it also occasionally skips, but not too bad, and also plays fine sideways and upside down).

When I get my digicam next week, I'll take some pics to explain what I mean. My fudge-repair is by no means a perfect repair, I don't even expect it to be reliable... but for now, it works great.

Graham Baker follows this advice to fix an MZ-R2

A user asks:

Hi, recently I am having some TOC reading problem with my old MZ-R2. It can only read the disc while it is on its side or upside down. (Common problem for old MD walkman) My question is, can I fix that myself? I remember someone here mentioned before that, one can tighten up the spring under the lens. Can you guys give me more info? I can open up the walkman, and tried to secure the screws inside, but it doesn't help. I certainly won't take it back to Sony Service, due to the high price, and afterall, I got 2 other MD player and recorder already. Thanks for any input.

Graham replies:

My MZ-R2 is doing similar things, but mine will not play, even when turned upside down or whatever orientation. It just skips & stutters continuously and then comes up with 'disc error'. I recently had it in for repairs but didn't go ahead with them due to a quote of $450 Aus for a new optical block.

I have been playing around with the lens suspension for the last few weeks and I think I can say that it is now 95% fixed. I took it apart (carefully!) and using a magnifier I was able to find the small white plastic (nylon?) suspension. I experimented by placing a minute blob of silicone sealant across the hinged portion of the suspension. Unfortunately the blob was too big and it made the suspension too rigid resulting in total no play and continuous and instant 'disc err' messages. On close inspection I found I had also stuck the tiny 4 wire flat cable to the suspension! So, after a lot of messing around, freeing up the suspension by poking about with a jewellers screwdriver I have got it to the stage where it now records and plays almost perfectly.

The only time I have trouble is first thing on a cold morning when it coughs & stutters quite a lot (a bit like me!) before settling down and playing. I would guess that the suspension is still a shade too firm, hence the cold weather making it just that bit too firm to focus correctly. Once it has warmed up it plays perfect all day. I suppose I could play around a bit more and it would be 100% but I am happy with it as is and sick of taking it apart and reassembling!

In retrospect I would say that it would have been better to use something other than the silicone sealant as once it is placed it is almost impossible to remove. Perhaps a minute piece of adhesive tape would have been better but it is very tricky to place anything on the suspension accurately.

So, IMO, Shawn's theory is correct - the Sony plastic suspension is probably the main culprit of many MZ-R2 & MZ-R3 failures. One thing that puzzles me is that I cannot find any adjusting pots of any kind for laser output etc. This is probably just as well as I do not have the service manual and I am reluctant to pay the $55 Aus for one. So, I have saved $450 and have a 95% good MZ-R2 once more

If you attempt this be aware: The circuit boards and the fine printed connecting wires are extremely static sensitive - best use a grounding wrist strap. If you power up whilst the covers are removed you could damage your eyes by looking directly into the laser/lens.

Good luck,
Graham Baker

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