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Old 30th March 2012, 06:39 AM   #21
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by PlasticIsGood View Post
Sorry, I mean the motor runs forward, fast. Not like pressing the fast forward key. The buttons all click and work as far as expected with no CD loaded and the motor permanently running. It's not an earthing thing either, and the boards are all seated properly and appear relaxed.

Having solved the problems it had when I got it, I'm now upset and it's in disgrace. I'll look at it again when I feel calmer. Thanks all the same.

Ian
It has to be something physical if this happens when the front is fitted. Loss of a rail or a clock or data signal... could be many things but hopefully a little careful prodding and bending of the boards will locate the area.

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I think we agree that the processor is not getting the right information. The problem is why not.

I'm surprised that the machine relies entirely on feedback from the laser to determine its spin speed. I'd assumed two nested loops, with the inner one derived from the motor itself. Oh well...logic isn't always the best guide.
When the laser initially finds focus on the stationery disc (stationery because it's easier to find focus on a still rather than moving object), the disc is spun or "kicked" up to an approximate running speed. A clock signal is now extracted from the signal off disc and compared to an internal crystal generated clock. From the difference between the two an error signal is determined that is used to alter the motor speed and bring the two together. That is called CLV or constant linear velocity and why the disc slows down as it tracks toward the outer edge. So the speed is crystal controlled.

So for any disc to spin up and play means that initial focus has been found. The player will have a FOK (focus OK) signal proably marked on the system control/servo IC/s.
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Old 30th March 2012, 10:37 AM   #22
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Originally Posted by Mooly View Post
That is called CLV or constant linear velocity and why the disc slows down as it tracks toward the outer edge. So the speed is crystal controlled.
Exactly that's the answer. The CD's are recorded CLV (means that the Linear Speed is constant, loop controlled), but people tend to think it is CAV (constant RPM, like in an LP disc).
CD cannot work without a focus. It will "start" in a certain position, at a certain speed, where it "knows" what RPM is expected to be (beginning of the disc, inner part), but further than that, the loop it really needs the feedback signal from the laser to extract the Linear Speed information.
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Old 31st March 2012, 09:51 AM   #23
Sonus is offline Sonus  Singapore
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Hi, just to share some encounters on my CD6000ose KI. Few weeks ago i done some cap replacing but had reversed the polarity of one of the cap that link to a 7918 regulator. When it power up it able to detect the cd and play along. But around mid track the cap burst. I try my luck by replacing just the cap with correct polarity inserted. The cd able to load into but does not spin. So replace the voltage regulator solve the spinning issue.

My cdp had been having cd reading issues for quite sometime and strange enough i did not notice the sound had became very dull and lack of details till i connect to my Audioengine A5+ for a listen. So yesterday i bought a new lens and replace it. Wow, the details and musicality had come back. Today i had let it run-in couple of albums, the sound start to smoothen out cos' initial play sounds harsh and bright.

ps My cdp had been chuck one side for almost 3 yrs till i bring it out for improvement project. Thanks for reading.
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Old 31st March 2012, 10:34 AM   #24
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OK guys, it has been fixed.

I took out the laser unit from an old Philips CD692 which by chance had the same VAM1201 unit. Since that was a Cd player which I found at the local garbage dump (and in still working condition!), I cannibalized it for the laser unit.

The Marantz recognizes now everything. CD-A and CD-R.

Now I need to wait when my DAC kit arrives from China, and make a very nice CD player.

Thanks for all the help guiding me into the correct way.


Haik
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Old 31st March 2012, 01:35 PM   #25
Mooly is offline Mooly  United Kingdom
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Pleased to hear you have fixed it.
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Old 1st April 2012, 09:03 PM   #26
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Quote:
Originally Posted by Mooly View Post
It has to be something physical ...
I think you're right. I replaced it with the Kenwood but neither shame nor jealousy has made any difference. Actually the problem's become permanent, which I'm a bit happier about. I've determined that the motor control signal from the decoder chip is set at full duty cycle, which is where it goes normally when accelerating from stationary, i.e maximum "too slow" error.

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if this happens when the front is fitted. Loss of a rail or a clock or data signal... could be many things but hopefully a little careful prodding and bending of the boards will locate the area.
I suspect the ribbons between folded boards. There's two connections from the front panel processor to the servo processor, and several to the loader microswitches, so I'll look around there when I've got manual and plenty of time. I won't learn if I blunder on regardless.

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When the laser initially finds focus on the stationery disc (stationery because it's easier to find focus on a still rather than moving object), the disc is spun or "kicked" up to an approximate running speed.
Mine gets permanently kicked, focus or not

Quote:
Originally Posted by Mooly View Post
A clock signal is now extracted from the signal off disc and compared to an internal crystal generated clock. From the difference between the two an error signal is determined that is used to alter the motor speed and bring the two together. That is called CLV or constant linear velocity and why the disc slows down as it tracks toward the outer edge. So the speed is crystal controlled.
That follows from sensible constant data density and inevitable constant demand for data. The only external signal to the motor driver comes from the decoder chip.

But that chip gets signals concerning the motor from sources other than the laser circuit, and I guess they depend in part on the front panel processor. Specifically, there should be a not(motor stop) signal (dead man's handle). At least there is on the CDM2 machines I worked on before I settled on the CD50.

Quote:
Originally Posted by Mooly View Post
So for any disc to spin up and play means that initial focus has been found. The player will have a FOK (focus OK) signal proably marked on the system control/servo IC/s.
Not as such AFAICS but I have no manual for the CD50 or anything with the same mech. I've just arrived at the CDM4 and wish I'd kept an earlier machine with better quality plastic.

cheers, Ian
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Old 2nd April 2012, 06:38 AM   #27
Mooly is offline Mooly  United Kingdom
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A good procedure is to pull the data sheets for all the IC's and to work around each pin in turn checking that every pin has the expected voltages/signals/clock etc.I always used a scope for that, even for DC voltages. You check everything... even ground pins. Do the same for ribbon connectors checking their source and destinations with a scope.

Good luck with it when you get around to working on it.
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Old 3rd April 2012, 02:49 PM   #28
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Thanks for your help, Mooly.

Ian
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Old 7th January 2013, 08:17 AM   #29
T Leung is offline T Leung  Hong Kong
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Marantz CD4000 is a good cdp.
I would say CAS is the trend. A good DAC (esp. DIY KIT ) may not cost so much more than the laser or lens assembly

Last edited by T Leung; 7th January 2013 at 08:45 AM.
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