Problems with the Mark Levinson 390s CD player - a possible design flaw?

[Barry]

True, the Levinson ML 390S uses a Philips laser reader: the CDM12 Industrial. Taken from the HiFi Advice site:

Not only Philips and Maranz used these transports: various other players were outfitted with these massive cast-iron swing-arm Rodenstock glass-lens mechanisms. Today, many of these products are still around, spinning CD’s as happily as before. They still produce excellent sound and as it turns out these transports are virtually indestructible.

CDM 12 IND (1994)



Of the various CDM12 incarnations, especially worth mentioning is the CDM12 IND, short for Industrial. This was the first generation of the CD Pro family of professional compact disc modules. It was the first to include a heavy die-cast metal frame and a servo/decoder circuit board as an integral part of the module. This mechanism was very successful in the high-end audio market as well as in the jukebox market, because of its robustness and reliability. The CDM12 Industrial can be identified by its extension plate, which reads “CDM 12 Industrial.” It’s model number will read “AH03.”

While it may seem that the CMD12 IND is nothing more than a cheap transport with a fancy housing, there are certain other details that have been improved such as double metal guide rails instead of the plastic slide pad of the cheaper models. Also, the CDM12 IND is fitted with a full metal spindle/disc turntable. This is an important aspect for its longevity because the plastic CDPro turntables had a tendency to crack over time.

The CDM12 IND is pin-compatible with the later CDPro and CDPro2 mechanisms. Also, the laser pickup part inside is compatible with that of a wide range of CDM12 mechanisms, such as the CDM12.4. While the turntable motor is not a part that tends to break down, it is also compatible with that of the simpler mechanisms.

[Macca]

Does it need to be 'virtually indestructible'? What sort of use-case will put that to the test?

Laser will eventually start losing power and although that can be tweaked to stave off death a little longer, it will eventually start struggling to read and need binning even if the mechanical parts will linger on in landfill until the sun dies.

[Barry]

The phrase "virtually indestructible" was that of the author of the post from the HiFi Advice site I cribbed. Agree, when it comes to domestic audio gear, such a requirement is unnecessary. But as it was one of the first series of laser mechanisms developed by Philips, they probably pulled out all of the stops to develop as reliable a product as possible; especially as they had the professional and CD juke box market in mind.

Regarding the lifetime of the laser, the MTBF of the diode is 25,000 to 50,000 hours, depending on the current driven through it. One of the reasons for laser diode 'failure' is not failure of the chip itself, but of the oft-used plastic lens which, with time, becomes statically charged and attracts dust affecting the ability of the device to read the disc. Readers fitted with glass lenses, such as the Philips CDM-12 (Industrial) do not suffer from this problem, and their lifetime can be many decades.

But let's stay with a figure of 25,000 hours - that's at least the playing time of 25,000 CDs.

[Macca]

The phrase "virtually indestructible" was that of the author of the post from the HiFi Advice site I cribbed. Agree, when it comes to domestic audio gear, such a requirement is unnecessary. But as it was one of the first series of laser mechanisms developed by Philips, they probably pulled out all of the stops to develop as reliable a product as possible; especially as they had the professional and CD juke box market in mind.

Regarding the lifetime of the laser, the MTBF of the diode is 25,000 to 50,000 hours, depending on the current driven through it. One of the reasons for laser diode 'failure' is not failure of the chip itself, but of the oft-used plastic lens which, with time, becomes statically charged and attracts dust affecting the ability of the device to read the disc. Readers fitted with glass lenses, such as the Philips CDM-12 (Industrial) do not suffer from this problem, and their lifetime can be many decades.

But let's stay with a figure of 25,000 hours - that's at least the playing time of 25,000 CDs.

Yes a low hours one isn't going to fail anytime soon. Things like belts and plastic cogs go before the laser does so good build quality isn't pointless. But there's a limit to how good it needs to be for the purpose.

No-one ever used the CD jukebox in my Uncle's pub because it was too expensive so that mech had an easy ride.