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-   -   Distorted output towards end of discs (http://www.diyaudio.com/forums/digital-source/212687-distorted-output-towards-end-discs.html)

Kei 15th May 2012 11:11 AM

Distorted output towards end of discs
 
I've got a clarion CD changer (CDC1235) that starts to distort/crackle on tracks towards the end of discs. It gets worse the further out it goes ending in a read error. (error 3) It'll read the TOC and the first 5-10 tracks fine then the distortion starts.

Here is a video that shows the problem. (that is playing a clean original cd that plays fine in all my other cd players)
YouTube video

I've dismantled it and cleaned all the gears and runners to no avail. I've then swapped all the motors and gears out for spares that i had lying around and still no better. (known working)

Would i be right in thinking that it's going to be the pickup causing the issue?

KatieandDad 15th May 2012 12:04 PM

This could be caused by a hairline fracture in the ribbon cable to the laser pick-up.

sesebe 15th May 2012 02:22 PM

My CD player (#1) have the same behaviour after I repared the servo system and now need calibration of procesor of servo. In you case it is possible (if the CD-player it is old) to have electrolitic capacitors with problems.

KatieandDad 15th May 2012 02:33 PM

Unlikely as it works for the first 3/4 of the disk. This is most likely a mechanical problem.

Ian Finch 15th May 2012 06:54 PM

I once had a stack of various mid-fi players with this fault. IME, it is the most common reason they are binned. The problems have been diagnosed differently by other techs but it comes down to the distance between sensor and disc varying across the play width and the focus servo not correcting it. Any slight disc warp is also accentuated by greater radial distance. 5-disc carousel players are notorious for this and all read problems,

I used to think this was just a laser alignment issue but never satisfactorily solved the problem this way, following service procedures. Replacing the laser assembly is expensive but usually did the trick in less time. I'm not proud of it but a Yamaha unit that I dropped, then began to work flawlessly and continued to for years afterward. I don't suggest the method but the mechanical issues can be this obvious.

Then, just a few days ago, I played a disc that was damaged but played fine up to track 3 then began to mistrack and continued to, right to the end and beyond the damage.
Why? If the disc was replayed, the sound began ok and if skipped forward to the final tracks, they played fine now too. It seems the error sensing has it's own set o problems.

Kei 15th May 2012 08:17 PM

A new pickup is available and not drastically expensive so if it's the most likely cause I can get hold of one. When i changed the spindle, the lower half of the clamp was also changed. When playing the discs do appear to wobble slightly though. (not that i can figure out why, as the discs appear to be flat.)

gfiandy 15th May 2012 09:18 PM

It sounds like the unit is interpolating data between successfully reads. This could be a problem with the ribbon to the laser but in my experience its more likely to be either the laser itself or the sled. I don't know the sled mech in this player but they can get stick. It sounds like you have tried this approach so I agree if a new laser is not too expensive it would be the next thing to try. But when you open it up look at the ribbon cable and see if there is any cracking of the foils inside assuming its the yellowy type foil its worth checking.

Regards,
Andrew

Ian Finch 15th May 2012 09:31 PM

Have a look at Mooly's earlier post detailing the refit and scope measurement for the Meridian with Philips transport. This gets complex when replacing just the pickup but if a pre-aligned assembly is available, take that option if the replacement is still necessary.

Kei 16th May 2012 09:26 AM

I haven't found any obvious damage to the ribbon, though there are two small scratches, but they don't appear to be deep enough to affect the conductors within. The transport is based on a sony CDXD2545Q and there doesn't appear to be any possible adjustments. (the old model of this unit used a different sony IC which did have adjustments for tracking and focus offset)


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