Noisy CDM

[Scorpio(DDMF)!]

One of my cdm4/19 (sourced from a Marantz CD41 player) has an annoying quality: it's a good bit louder when playing when compared to others...

The problem manifests itself like the increased spindle motor noise when playing.

The interesting thing is that it's noisiest when playing original (pressed) CDs, and relatively quiet (normal) when playing cdr and cdrws which leads me to believe noise is reflectabillity-related...

The mech itself works great and reads everything with no problem. It doesn't need much trimming to achieve the 50mV laser current optimum, from which I can conclude that the laser itself isn't in a bad shape.

So far, I have lubricated the spindle motor, transferred the arm to another (good) cdm4/19, switched players, but to no avail...

My last thought would be that some of the smd element/s on the arm itself has gone bad, but apart from resoldering them, I haven't done anything else about that (I'm not very optimistic about changing smd elements on a flex foil ).

Searching the board, I've found only one reference to the problem, but in an unrelated thread: http://www.diyaudio.com/forums/showt...929#post872929

Originally posted by 405man
I have a CD player that uses a Philips CDM4/!9 and when playing original CDs there is a chirping noise from the mechanism which is disc speed related when I play copied CDs the noise is considerably reduced or not present at all. This suggests that there is a difference in the amount of work the servo does with different discs. I have not yet had a chance to investigate further

Stuart

I would be grateful to any fresh insights.

Cheers!

[stephensank]

It'd been my experience with CDM4's that I need to use a number of different cd's(but not cd-r's), of a varying age/qualty as possible until I consistently stay within a 50-60mV window as much as possible. You may have the current level set toward one end of the spectrum, and, since the whole servo system relies on the current adjustment, it is therefore noisy with cd's at the other, probably more average, end of the spectrum of disc quality.

[Mooly]

Hi, Is there a "Focus Gain" adjustment.If the gain of the servo is too high a sound like "white noise" can come from the coils on the lens assembly.This is very noticeable on the KSS xxx and similar units.Does the noise disappear "between tracks" ? Edit Is the motor a hall effect type or D.C. type.
Regards Karl

[stephensank]

The later CDM-4 based units had a focus offset adj in addition to the previoulsy-solitary laser current(LD power adj measured by PD current, which is rather strange), but, anywhere near mech center on that adj has no real effect on performance or noise. It's all about getting the current adj into the right range on these guys.

[Scorpio(DDMF)!]

Thank you for the answers.

Hi Stephensank,

Since I don't have the required Philips Test Disc, all the calibrating is done with a cd which has the highest reflectivity in my collection - in this case, a pressing of Miles Davis's "Kind of blue" - this CD has been proved to cause the highest laser current when played.

Sadly, the "annoying whoosh" (a better term for the noise) doesn't decrease even if the laser current does (on pressed discs).

Also, I've tried the "by ear" method of adjusting where I play the disc while listening for "crackling" in the playback to determine the right laser current (by this method you can set lc a little lower, but some cdrw-s wont be played), but that hasn't lowered the transport noise.

Hi Mooly,

There is a focus offset adj. and it's adjusted to the SM recommended value: 400 mV (using the CD mentioned earlier).

The perceived noise doesn't disappear between tracks, also the CDM4/19 motor is a regular "toy motor"/w brushes.

Cheers!

[Scorpio(DDMF)!]

Any fresh takes on this?

[Malefoda]

Up for this,
any news?
Can't it be the top clamp? On mine it does a "schwiip schwippp" at each revolution, depending "mood".
When it makes noise it's too loud, no way to listen at music at late night, but an "open/close" can be enough to cure the noise...

So if anyone has a linked problem and even better any answer that would be great.

Regards,
Matthieu