What If The CD Player Doesn't LIKE The Disc?

All CDs are full of errors. The encoding scheme is designed to invisibly correct these errors, provided that the number of errors within a single block is less than the maximum the encoding scheme can handle. One player may be able to read a pit, or the absence of, better than another player. I think that in this case, your Magnavox reads enough errors in a single block so as to make it incorrectable. In most areas of the disk, this would simply produce a click. However, if the error is in the TOC (table of contents), it could glitch the firmware in the player.

Bob Morein (310) 237-6511

I'd say the CD player doesn't like the disc then.

The disc may be faulty in a way that matters to that player , but possibly not others. You get that...

geoff

Overall poor reflectivity of the CD (and thus a reduced contrast and reduced RF signal "eye" quality) might cause this. A player as old as the CDB650 might have two things working against it, with regard to such discs:

- It's old enough that it probably has a lot of hours on its laser. Output may be dropping, weakening the signal detected by the photodiode.

- It's pre-CDRW, which may very well mean that its photodiode/sensor circuitry doesn't have an AGC feature. If the problem is just one of poor reflectivity, there probably isn't much that can be done with regard to this particular CD player.

The disc could have other sorts of defects, too. Check the inner rim, and see if there's any excess plastic "flash" which makes the inner hole less than perfect. If so, it could prevent the disc from sitting evenly on the player's spindle - the disc might wobble when rotated, and be difficult for the laser/optic assembly to track properly.

--
Dave Platt                                    AE6EO
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Since the identity of your CD is apparently a secret, we have the option of speculating that it might be one of those (supposedly ordinary) discs they tried to put "copy-protection" or "digital-rights-management" on.

On 08/12/2008 08:21 PM, EADGBE sent:

Hello to All:

Wouldn't this be a good time to try a gentle lens cleaning per Sam Goldwasser's tips? Mfgr'd in 1980? Recently cleaned? Worth one last try I'd think...

Cheers to all.

--
1PW

@?6A62?FEH9:DE=6o2@=]4@> [r4o7t]

I'll second all that the others above have said, and agree with Geoff here. It's not at all unusual to see players that simply won't play - or have a lot of trouble playing - just one or two discs out of an owner's collection. I have had them send in players for repair with an example disc, and they are quite right, it won't play it, and of course, they have always "tried the disc in the neighbour's machine, and it's fine !"

But if the player is trouble free with every other disc that you - and they - put in it, including 'official' test discs with deliberate errors for checking servo performance etc, what can you do ? You can never see anything wrong with the eye pattern on such players, and I've even tried replacement lasers, without altering the symptoms a jot, so I think that it must be a case of too many errors for the player to correct, but who can tell ...

As you surmise, and Geoff says, the CD player just doesn't like the disc then :-)

You know, I've just had a thought. Long long time ago, I had a Pioneer that had playability problems just on certain discs. It's very very rare for Pioneers to suffer a bad laser, and the early ones are unpleasant to replace because of the diffraction grid adjustment that has to be done. I was loathe to suspect the laser, so I gave Pioneer Technical a call.

In those days, they had the best guys in Tech Support that you could ever wish for (they're actually still there, but a lot more difficult to get to talk to now). Anyways, I asked them about this problem, and they pointed me at the rubber deck suspensions, saying that the problem was caused by age, and them having collapsed some. As you might imagine, I was sceptical about this, but I ordered a set and fitted them, and lo! it cured it completely. I can only assume that with little or no suspension left, if a slightly eccentric or off balance disc was put in, instead of the whole deck being able to freely 'wobble', with the deck touching the sub-chassis, vibration was instead transferred to the lens suspension, making this vibrate at high speed.

Given the age of the player in question, might be worth a look at ??

Arfa

Hi, Geoff!

The problem with the insulators was just that the disc would "barely" scrape while trying to play. It was indeed a common problem; replaced many of them. Sometimes the drive IC would even brown the circuit board as a result.

To the OP regarding the one disc that would not play: try cleaning the disc itself - sometimes that helps - or perhaps the store you bought it from would let you try another copy.

As another poster suggested, cleaning the laser lens is certainly worth a try.

Magnavox (Philips) players were sometimes picky about discs, with nothing that could really be done about it. When people would complain, the standard response was, "the disc is out-of-spec, not our problem". A good example of this was the CD-63 series having problems with discs longer than 74 minutes.

Mark Z.

Yep. I have one from that series, and it chokes on many extended-length pressed CD's. There's a place in Connecticut that can modify the pickup circuit to handle off-spec discs better, but then CD-R playback suffers.

Thanks, as usual, for all the great info so far.

I forgot to mention that I did try cleaning the laser lens. I used

91% isopropyl alcohol, which usually works pretty well, unless there is a better method that I don't know about.

On Tue, 12 Aug 2008 20:21:15 -0700 (PDT), EADGBE put finger to keyboard and composed:

Whenever I have compatibility problems like this, I burn a copy of the disc. The copy usually plays flawlessly. If it doesn't, then I'd suspect something is wrong with the contents of the disc, perhaps copy protection as mentioned elsewhere. Is it possible that older players can't handle CDs with combined audio and data, and is your CD one of these?

- Franc Zabkar

--
Please remove one \'i\' from my address when replying by email.

I would ask how large the data is on it. Some players cannot handle a disc with more than 80 mins of audio on it. Some have a problem with more than 74 mins. I have a factory Madonna CD that is 74:30 and it will not play in one of my players, but it is fine in all the others. Audio CDs can contain up to 99 minutes of data (874MB), but they have to be carefully written at a very low speed.

- Tim -

On Wed, 13 Aug 2008 17:50:24 -0300, Tim put finger to keyboard and composed:

I have an old Philips/Marantz player that won't play 80 min CDs. As for wobble, ISTR I once played a CD that was either recorded eccentrically, or was not clamped centrally. The player's voice coil positioner visibly wobbled from side to side but tracked the disc perfectly.

- Franc Zabkar

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Please remove one \'i\' from my address when replying by email.

An option is to dupe it to a good quality CD-R. But if the laser is a bit 'down' it may not like CD-Rs either....

geoff

Should be adeqate, and if there was no obvious change one way or the other, the lens was probably clean enough.

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IPA is fine, although 'electronics grade' is usually a little purer than that at 99.7%

Arfa