temperature problem, which parts ?

[Bernhard]

Hi,

I have a CD player that needed 10 minutes to warm up before it liked to play a CD.
After changing the laser everything seems to be ok so far.
There are 3 small polarized lytic caps, one resistor, one transistor and a pot on the small pcb attached to the laser.
Is it the laser ?
I do not believe the whole thing does warm up much if the player is on stop ???

Other question, which discrete parts like to make crackling noise ?

[davidsrsb]

A Philips transport?

What might be happening is that as the laser degrades the feedback circuit increases the drive current to get a constant level from the monitor diode. The led modes will increase and the output beam may be less ideal, blurring the spot and causing the servo to become confused about focus.

I see the diode inputs to the servo go negative at startup even with the drive disconnected, which is hard to understand without a negative power supply. I suspect some strange bug in the DSIC ADCs. Many players over the years have used various generations of the DSIC eg TDA1301, with basically the same circuit. I am certain that there are signals from the diodes from disk reflection in my players, but the servo does not attempt to start the motor, so maybe the software requires valid focus to detect a disc and does not get this when cold.

[Bernhard]

It is a Yamaha CDX-5000 , no typo...
There is the laser power pot on the small pcb, so isn't the output constant ?
I have adjusted output power of both, old and used spare laser, so that when playing CDR, pickup makes no akustic noise.
It suddenly starts getting noisy above a certain amount of power.
Beside having the temperature problem, the original laser does not read CDR as good as the spare. But pot position is nearly the same on both.
I could change those small caps and put the old laser back but it is a horror to do it because the cables to the laser have very thin & sensitive wires and it is hard to remove the plugs on the pcb.
Laser is MLP7.