MZ-R50 no "Disc Error" only when playing upside down

[Robert L.]

Hello everyone

 

I recently bought a MZ-R50 in a nearly perfect condition. I was able to clean it inside, lubricating the worm gear, lens slide and also the lens with Isoprop alcohol. What I have recognized: when playing a pre-recorded MD all is perfect. The MZ-R50 reads instantly TOC and plays fine all tracks backwards and forth. However with recorded MDs it needs long time for TOC reading or showing Disc Error. Also when playing it's much busier in searching tracks. But when I turn the device upside down all is perfect as with pre-recorded MD's.

 

What I've meanwhile read in the Forums: pre-recorded MD's are reflecting the laser better than the recordable MD's. So as it plays pre-recorded MD's without any issues, would you recommend to perform the Test Mode so that the MO test routine align the laser new? 

 

I don't want to make it worse so any hint from the experienced  experts are welcome.

 

Thank you.

 

Best regards.

Robert 

[sfbp]

Hmmm the upside down sounds like some hairspring which holds things in place not needed when you invert. Check the assembly with the Service Manual very carefully.

[Robert L.]

Thanks sfbp for your quick reply. Unfortunately I didn't find anything special in the Service Manual. Question is what could hold a thing in place for a MO MD which is not needed for a CD MD, as the CD MD is playing absolutely fine. 

[sfbp]

(in the night, so maybe I won't make sense at all) That would tend to suggest something with the overwrite head. But generally playing a CD MD is a much easier assignment for the mechanism. That's why you do the CD alignment first as it is quite coarse by comparison with the MO. Have you actually done an align? I realise on these old models it's way less automated, but maybe you are more technically competent than I in such issues, and can do it.

 

Does it by chance erase the whole disk when you try to make a track mark? (obviously you'd better not put anything precious in it for that reason) That's an indicator of the OW head circuit being broken, usually a defect/crack in the very thin cable.

 

If not then I think your idea of running the align makes sense. I've never even done it on one of these oldies, so I had better defer to the experts who have. Because CD reading is completely different from MO reading, it's quite possible that the laser isn't working and your observation of it working correctly upside down is kind of "lucky".

 

Don't mind me too much, I am blathering and hand-waving at this point without too much content. If you have the gear to fix it, we shall be most interested to hear how your fixed it.

 

The other thing that might be gravity dependent is a micro-switch that depends on a spring? What does the second hole do? The one on the underside of the disk which is absent on a CD?

 

 

[imkidd57]

There are some very fine linear springs in the OPU assembly on which the lens 'hangs'. Focusing on the disc track is achieved by a small electrical coil linked to the lens, which moves the lens up and down until it obtains an authentic location address on the disc. It may be that something is impeding the coil from moving the lens upwards against the push of the springs, whereas with the unit upside down it gets assistance from gravity, as @sfbp says, to move further towards the disc surface. The CD discs could be read OK because the range of the lens is still within the tolerance, given the higher reflectivity and that the information is in the form of true pits and lands, rather than relying on the MO disc substrate polarisation effects to read an MO disc.

 

Some possibilities:

1. Lens is not completely clean
2. Something mechanical obstructing the lens movement and preventing the upwards travel
3. Weak circuit voltage which means the coils can't pull the lens up enough, against the force of the spring
4. A combination of undervoltage and weak laser

The first is easy to test: try cleaning the lens again, but this time with some distilled water. I have found that some isopropyl alcohol leaves a slight haze on the lens.

The second.. have a close look at the OPU under magnification and check for hairs or dust that might be interfering with the lens travel

The third and fourth: this will probably require the adjustment procedure of the unit, but for the MZ-R50 is requires a bit of soldering to get it into test mode; it can't be done from the remote as for newer models. Before doing this though, one thing may be worth trying. With a full battery, open and close the lid of the MZ-R50 without an MD in it, and leave closed for around 30 sec; then repeat this 15-20 times. This action forces the OPU mechanism to move the lens up and down to its fullest extent either side, to check if a disc has been inserted, and it may be that a bit of 'exercise' might be of benefit. If your unit is in near mint condition, then it may not have been used very much for a long time and so using it more could free things up.

 

[sfbp]

There's an answer I could never have given. Well done! Certainly sounds like it fits the observed behaviour.