On Thu, 08 Jan 2015 23:27:40 -0800, jurb6006 wrote:

Also, there is the possibility of a bad motor driver. This is not always
an IC. It oculd be just a ocuple of transistors. If the spindle motor
starts pulling too much current it can blow the driver. If in doubt,
follow it back to whatever drives the motor to see if it is getitng
dsrive but not driving. In that case the spindle motor might be bad.

The circuit is usually simple as hell. It is off when the buffer is
almost full and on when the buffer is almost empty. And a transistor
maybe for braking, if it even has that it usually just shorts out the
motor so to load it and stop the disc. They don't use a negative voltage
usually they just calculate the mass of the disk and with the motor
loaded by the short it must stop ithin a certain time.

You say it is a combo unit ? Expect the absolute cheapest of circuitry.
In fact if it has a pop up door instead of a drawer it probably has no
braking and just has one transistor to drive the motor, on or off. Might
even be a DTC something because the current is low.

Or supposed to be.

If you can get a print and find the FOK line and check it that is fine,
but if whatever drives that motor is not told to turn on you can pretty
much assume you don't have it.

I would clean the laser. what's more if you clean the laser and it
starts working, tap on it with a screwdriver handle or something and see
if it skips easily. then you got a weak laser. It will work for a time,
BUT it is regulated so it will not last.

If you decide to tweak up the laser power ith that little pot, remember
it is not going to last long and probably will still skip easily until
it fails.

It is nice practice probaably fixing those thihgs but you are not goiung
to make a fortune at it. Also, in some cases you can get the whole CD
drive for about the cost of the laser. (I had a bad new one once and had
to frankenstein the damn thing between parts from the new and old
because the job had to go out, piece of ****)

Thanks very much to all three of you for your comprehensive answers.

The unit is an Alba CX500L which is a budget brand and I haven't been able
to find any schematics or service manual. So I have left the four tweaking
pots on the PCB strictly alone! They are marked only with schematic IDs.
However the PCB does have numerous test points marked so I may play a bit
more... Also the actuator and spindle motor drivers are combined in IC
KA9259D and I have a specification sheet for that.

This is merely a learning hobby exercise. As soon as it gets too boring
the unit will get junked; I am unlikely to spend any money on it!

Mike.