Radio interference-like fault on CD playback.

[pastedavid]

Hi,

I have two Sony CD playes (one in a midi system, one stand alone) which, with a small number of CDs, produce a strange slightly-untuned-like interference. Both of the CD players use the KSS-213 laser pick up, if that is of any relevence (B version on the older midi sytem, C version on the seperates player).

Can anyone shed any light on to what might be happening? A laser unti about to expire, perhaps?

Thanks in advance,

David PAste.

 

[Mooly]

Seems a bit strange if both players exhibit the same symptom (is it on the same discs ?)

Hard to say what's going without at least some basic check of the RF on a scope, comparing a disc with the problem to one without. It sounds from the description faintly like the effect you might get when the recovered amplitude of RF is low.

 

[pastedavid]

Hi! Thanks for the quick reply!

Yes, it is with the same discs. The discs have more than the 74 minutes of a 'standard' CD - one has just under 78 minutes of audio on it (I just checked) - would this point to anything?

I'm afraid I don't really fully understand your second paragraph.

Thanks again.

 

[Mooly]

Well you see, without measurements its all guesswork with no real handle on what the issue is.

Measuring the RF (or eye pattern) means looking at the signal from the pickup. The pictures in post #1 here show the RF being measured and adjusted for real,

http://www.diyaudio.com/forums/digital-source/226288-sony-cdp790-kss240-restoration-project.html

Only by looking at that is it possible to get an idea of what is happening. If the amplitude were low then that could be a pickup issue, or it could be mis-adjustment of one of the servo presets.

Some discs (rare but it happens) have poor reflectivity which reduces the level of signal, but that is not related to total playing time of the disc. I take it you have cleaned the lens on the pickup ?

Without a scope you are very limited as to what you can diagnose and repair.

 

[pastedavid]

Yeah, cleaned the lens. It was not reading anything previous to that, but cleaning it brought it back into good use.

Thanks anyway.

 

[Mooly]

I suppose it might be worth trying a new pickup, the KSS213 is cheap and easy to fit.

I would caution that and add on the proviso the player is otherwise "original" and hasn't had any presets altered or adjusted. If it has then you need a scope.

 

[pastedavid]

Well, the player is original, except for a couple of drive bands, but...

...on further investigation, it looks most likely that it's the CD which is knackered. I tried to make an image of it in EAC yesterday, the burst mode simply replicated the distortion as heard through the CD player, and the secure mode of EAC wouldn't read it, simply kept reporting errors.

The disc is not scratched at all.

Then I remember when I ripped the disc to MP3 years ago, it took EAC (albeit on an older PC and an earlier version of EAC) nearly 10 hours to complete. So it seems that the disc has got progressivley worse over the years. Ho hum.

Thanks for your input, I appreciate it!

 

[Mooly]

Thanks for the update.

I've seen odd discs deteriorate like you describe but it is fairly rare in my experience. If you hold it up to the light can you see any excessive opacity or even holes in the reflective layer.

 

[pastedavid]

Well, I've looked and looked, but nothing yet. The thing is, the artwork on the other side might be interfering with it, so I'm just not sure. I might put it on my scanner when I get chance, see if that can pick up anything unusual.

 

[Mooly]

I seem to remember something about certain inks damaging the reflective layer. Discs with reflectivity problems sometimes look less slivery and take on a more yellowed appearance.

Try googling "disc rot"

Disc rot - Wikipedia, the free encyclopedia

Compact Disc bronzing - Wikipedia, the free encyclopedia