Denon UD-M31 CD Problem

Are you sure the drive motor is good? If it is 'twitching' as you suggest, it just may be bad. I expect it is a Hall Effect motor with the speed fixed by the clock. So, either the motor or the clock should be on your list of suspects. Do you get output to the motor?

This is, after all, a mini-system, and so may not be as rugged or as easily serviced as a stand-alone CD player.

Peter Wieck Melrose Park, PA

, it just may be bad. I expect it is a Hall Effect motor with the speed fix ed by the clock. So, either the motor or the clock should be on your list o f suspects. Do you get output to the motor?

ly serviced as a stand-alone CD player.

Thanks for the reply. I have replaced the entire CD mechanism and so have replaced the motor. I believe that the sequence is as follows:

1. Laser turns on
2. Focus adjustment
3. Motor will start if focus is OK, PLL is OK and RF output is present. I have clock (from the chip). Focus is active (lens moves) but I have no RF and the APC of the chip is not going low. Can happily email schematic and datasheet is it would help. Regards, Rupert

Check the motor driver IC. I have had these go bad from faulty motors. With the mechanism replacement, you now have a new motor, but not a new driver IC.

Dan

Calling all CD repair experts! This is my first in depth CD repair and I have the following questions: I have the above unit, that won't play CD's. I have replaced the laser mech and still have the same fault. The CD will 'twitch' but not run up to speed. Using service mode I am monitoring the output from pin 62 IC802 and it never seems to go low (thus powering the laser). Clock, data, CS and all Vcc lines are correct and the chip is being told to turn on from the processor. I have also checked the operation of TR806. Has anyone had experience of these IC's failing or is there another possible cause? Please let me know if I have missed anything! Regards, Rupert

Where did you get the mech from and how much did you pay for it?

I've bought many lasers from ebay that just don't work. That's why they are so cheap and on Ebay.

Gareth.

Thanks Dan, The motor is driven from the analog signal processor that I was asking about, but as the motor does move I guess that it is getting some signals?

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Hi Gareth, The motor was from ebay but from a supplier that I have used before and not had any problems with. What are the chances of replacing a unit and having exactly the same fault as the origional? Thanks for the idea though I am n ot ruleing anything out at the moment!

out, but as the motor does move I guess that it is getting some signals?

Look at the BA6287F IC. This is hte motor driver IC and is separate from t he signal processor. The signal processor will trigger the driver, but the driver itself may be the problem. If the driver has been weakened or damag ed because of a bad motor, it may not be able to drive the new one either.

The way these work is that the CD needs to spin up to a certain speed in a particular period of time, before the focus takes place and an attempt to r ead the TOC happens. If you are just getting a short shake of the CD, I wo uld start with the motor driver.

Hi Gareth, The motor was from ebay but from a supplier that I have used before and not had any problems with. What are the chances of replacing a unit and having exactly the same fault as the origional? Thanks for the idea though I am not ruleing anything out at the moment!

Those chances are IMHO reasonable. There is a lot of fake s**te out there.

Think Occam's razor before suspecting pin blah blah on IC blah.

Gareth.

And I assume you have removed the soldered safety short that is shipped with a new laser pickup before trying to use it?

Gareth.

about, but as the motor does move I guess that it is getting some signals?

the signal processor. The signal processor will trigger the driver, but th e driver itself may be the problem. If the driver has been weakened or dam aged because of a bad motor, it may not be able to drive the new one either .

a particular period of time, before the focus takes place and an attempt to read the TOC happens. If you are just getting a short shake of the CD, I would start with the motor driver.

Thanks for the reply. Is this routine particular to Denon as I was working on the startup sequence (as follows) from

1. Drawer closes.
2. Interlock (if present) engages.
3. Pickup resets to starting (index).
4. Laser is turned on and focus search routine is started.
5. Disc starts spinning up to 500 rpm and Constant Linear Velocity (CLV) se rvo is activated.
6. Tracking servo is activated to maintain laser beam centered on track.
7. At this point, data is available for digital processing.
8. Disc directory is read and displayed.

Thus I am assuming that if I get no output to turn on the laser then I will fail focus (I can not find an external focus OK on the driver). Without fo cus then the disk will not start. This is what is confusing me as I believe d that to spin the pre-requirements were that focus is locked and there is a clock present ready to phase lock with the data coming from the disk.

Would love to hear your comments and thoughts on this as I may have the who le thing wrong in my mind.

Regards, Rupert

Yes, I did remove the solder blob when I installed the replacement.

I don't know about this particular system, but some attempt to spin the disk PRIOR to the focus. The laser can detect its reflection without needing to be in focus. You may not see the focus attempt before the spinning.

Dan

Thanks Dan, Very interesting - I have ordered both the driver and the ASP from Denon. Will update the post when I get the spares. Best regards, Rupert

disk PRIOR to the focus. The laser can detect its reflection without needi ng to be in focus. You may not see the focus attempt before the spinning.

Hello Rupert, how did it work? I have same issue. First of all. i have UD-M30 on which the tray would not open. I found sort of loosen rubber belt. Replaced it and everything was ok . then, as we dont listen to cds very often, it got loosen again (the belt) a nd i decided to replace it as i had same from previous purchase. Found out that after inserting cd it does not spin. Only spin it does for l ike a second is when i switch to CD from previous TAPE source.

Meanwhile i ordered the whole mechanism, so perhaps it will help.

That was five (5) years ago. But:

Generalized warning: OEM belts for obsolete equipment are generally a bad c hoice, as those parts in may cases are as old and have sat around just as l ong as the parts inside the unit. I have had 100% success ordering generic O-rings from McMaster-Carr to the correct size, configuration and diameter (and at a fraction of the OEM cost). I have a choice of materials, O, [], D , 0 or otherwise, even toothed, and they are fresh.

Peter Wieck Melrose Park, PA

choice, as those parts in may cases are as old and have sat around just as long as the parts inside the unit. I have had 100% success ordering generi c O-rings from McMaster-Carr to the correct size, configuration and diamete r (and at a fraction of the OEM cost). I have a choice of materials, O, [], D, 0 or otherwise, even toothed, and they are fresh.

And? Got mine problem now, so what is the big deal?