CD player not recognizing disc

[jarthel]

When I insert a CD, it just say "No Disc".

It was working 1 minute and suddenly the player stop working.

I opened the chassis and have traced the wires for the motors.

When I open the tray, the voltage going to the tray motor jumps from 0V to -2.5V. When I close it, it jumps from 0V to +2.5V.

I know that for a CD to be recognize, the player does an initial spin after closing the tray. This is not happening for my player. When I measured the voltage going to the motor that spins the CDs, it remains constant at 30mV.

Any ideas?

Thanks for the replies.

ps. from memory it uses the PHILIPS CDM1210 transport if that helps

 

[hacknet]

its probably a wonky lens. the symtoms all sound right...

 

[jarthel]

Would cotton with some isopropyl alcohol works?
---------
I still have my doubts the lens is at fault. For the player to recognize the CD, the CD spins for a short time after the tray is closed. During this spin process, the lens would then works its magic to recognize that the CD inserted is an audio CD. Since the CD is not spinning, the lens is never given the chance to work.

These are just assumptions though but it seemed logical to me.

 

[tubenut]

Depends...Check the limit switch, also some mechs focus first, then spin like CDM9

whereas CDM4 spin before focus.
Please check the limit switch(es) on the loader tray.
The switch is what initialises reading of TOC.

Good luck

 

[jarthel]

Re: Depends...Check the limit switch, also some mechs focus first, then spin like CDM9

whereas CDM4 spin before focus.
Please check the limit switch(es) on the loader tray.
The switch is what initialises reading of TOC.

Good luck

where will I find them? How will I identify this switch? Thanks

 

[tubenut]

Look near the front and back top right edges of the loader (CD face plate facing you). I am not familiar with the 12.XX versions of Philips lasers.
Look for 3 brass terminals. Generally only 2 terminals are wired up.
If you manually slide the tray open and closed, look for a plastic "finger" that gets pushed in and out. CDM4 uses 2 switches, one to sense open and one senses closed. CDM9 does this with one switch at the top front right of the loader.
On the CDM4/19 this switch is a PCB mounted push button below the mech linked to the tray with a complex lever system.

Sliding the tray in and out and looking carefully at what moves and pops in and out of place there should be a good chance to ID the switch. Look for wires going to the PCB from the mech. There are only a few sets:
Spindle motor, Tray motor, Laser (but that is a foil) and the tray switch (if not a pcb mount affair)!

If you want to clean the lens use distilled water, isoprop can take some protective/glare coat of the lens according to some on this forum!!! If you have none at hand, boil a kettle and catch some steam on a cotton bud..

 

[jarthel]

thank you. I'll try that