MZ-R91: Loud mechanical noise during playback (different depending on battery or wallwart)

[pastic]

Hi!

My MZ-R91 is making ugly mechanical noises during playback. The other day I resurrected it from a box in our cellar. It makes a very loud mechanical noise when I play minidiscs (any of the 72 discs that I own). There are two kinds of noise: one intermittent at regular intervals during playback when powered by battery, and one constant during playback when powered by original Sony wall-wart (though sometimes there is about 50 seconds of initial silence before the constant mechanical noise begins, see 2a below).

The unit’s been in a box in the basement for about 10 years, and I can remember that back in the days there was the intermittent noise (1) when powered by battery, but I can’t remember the constant noise (2) when powered by wall-wart. And I don’t think it made any noise at all when I bought it new in 2000.

I have made a few recordings of the two noises, one could be normal but the second I think is not:

1) The first sounds as if a motor is revving up and then down after a few seconds. The whole thing lasts 10 seconds. This sound can be heard when I put in a minidisc into the unit and also when navigating between tracks, so I am thinking it could be normal. However, this revving up/down comes back at regular intervals every 50 seconds during playback when powered by battery. Then the unit goes silent for another 50 seconds before it revs up/down again, and so on. It is irritating because you can hear the revving through the music.

2) The second sound is the most irritating and it appears only when the unit is powered by wall-wart. Basically, after the initial 10 second revving when initiating playback, it never revs down but keeps revving through the entire playback session.

2a) A peculiarity when powered by wall-wart: when I stop playback the revving sound is heard before the unit comes to a halt. However, if I immediately re-initiate playback the unit will play silently for 50 seconds, after which it revs up, but instead of revving down after 10 seconds it just keeps on revving and remains throughout the entire listening session. Every minute there is some strange rapid sound, after which it keeps revving for another minute and so on and so forth. This initial silence proves that the unit is capable of silent playback also when powered by wall-wart, but only for 50 seconds until the first revving cycle.

Does anyone have a clue as to what kind of noises these are? Might I be able to repair the unit myself? (I found the service manual on this great site)

I would greatly appreciate any help!

 

Noise recordings @ SoundCloud with time notations explaning the sounds heard:

https://soundcloud.com/user-514969654/md-battery

https://soundcloud.com/user-514969654/md-wallwart

https://soundcloud.com/user-514969654/md-navigating-tracks

 

 

[sfbp]

One of the gears needs lubricating or replacing.

The silence is because the music is buffered (read into memory ahead of time).

[pastic]

On 1/14/2016 at 3:37 PM, sfbp said:

One of the gears needs lubricating or replacing.

The silence is because the music is buffered (read into memory ahead of time).

Thanks!

(So it doesn't buffer when powered by mains/wall-wart?)

Do you think it would be stupid of me to try disassembling and lucricating myself? I am not prepared to pay for servicing it, so either I a) fix it myself, try to sell it "noisy, but working", or c) wrap it in sound dampening cloth and putting it in a drawer (that's the only way I can't hear it when it plays.)

 

[sfbp]

The only problem might be if the gear is partially stripped.

You'd need the right lubricant and hopefully you have some experience working with tiny equipment.

We had an expert in such things but he doesn't come by here any more.

Prepare yourself for an adventure ... we will try to help. The best means to learn stuff like this is to compare with a working unit, which in some respects defeats the point. But nevertheless may be your best strategy. They are not hard to find.

[sanchaz12]

Yes, I know this is an old topic, but I want to share my experience with others facing the same 'issue'.

From what I can remember, my MZ-R70 has always produced a mechanical noise (still does) but works perfectly fine. It sounds exactly as in your recordings on SoundCloud.
It is even mentioned in the manual (page 44 of the R90/R91 manual and also in the R70 manual);

"Note on mechanical noise
The recorder gives off mechanical noise while operating, which is caused by the power-saving system of the recorder and it is not a problem."

The fact they had to put it in the manual suggests to me that the noise was louder than people would expect.
As long as it doesn't sound like a grinding/clicking sound I would not worry about it.

EDIT

Below I've attached a recording of my MZ-R70 when the lid is being closed. It reads the MD and buffers the ~40 seconds of music of the first track.

MZ-R70 noise.mp3

[PhilippeC]

Sound like a vacuum cleaner your MZ-R70...

[sfbp]

One comment: any time a MD recorder makes noise, the battery playing time will be significantly reduced. On the super light weight models (eg my E909 and on the E10 I imagine) this can prevent playback completely especially in MDLP modes. There is no service procedure specifically - just engineering common sense as to how you reassemble it, which take patience and practice to get right.

Kind regards