Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Old June 14th 16, 06:53 PM posted to sci.electronics.repair
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Default Denon UD-M31 CD Problem

On Monday, 13 June 2016 21:52:24 UTC+1, wrote:
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?


Look at the BA6287F IC. This is hte motor driver IC and is separate from the signal processor. The signal processor will trigger the driver, but the driver itself may be the problem. If the driver has been weakened or damaged 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 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 http://www.repairfaq.org/sam/cdfaq.htm#cdstupseq

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) servo 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 focus then the disk will not start. This is what is confusing me as I believed 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 whole thing wrong in my mind.

Regards,
Rupert

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Old June 14th 16, 06:54 PM posted to sci.electronics.repair
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Default Denon UD-M31 CD Problem

On Monday, 13 June 2016 22:17:01 UTC+1, Gareth Magennis wrote:
And I assume you have removed the soldered safety short that is shipped with
a new laser pickup before trying to use it?


Gareth.


Yes, I did remove the solder blob when I installed the replacement.
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Old June 14th 16, 07:13 PM posted to sci.electronics.repair
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Default Denon UD-M31 CD Problem

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
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Old June 14th 16, 10:25 PM posted to sci.electronics.repair
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Default Denon UD-M31 CD Problem

On Tuesday, 14 June 2016 18:13:21 UTC+1, wrote:
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


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