General > General Technical Chat

The Curse of the Old Music CD Player: Optics or Motors?

(1/7) > >>

.o:0|O|0:o.:
I am about to open up several faulty music cd players (protable and small kitchen type stereos). They all seem to have a similar problem, the "signs and symptoms", as it were, are very similar, and all of the units just seemed to have died of old age; i.e., they never sustained any trauma or damage.

When you put the CD in, the base motor rotates for a while and the other motor moves the laser diode up and down a couple of times before failing to establish a connection, and eventually it eventually gives up. Some units display "error", some display "no disk", some just turn off.

While the CD is spinning, you can even skip through the tracks, but the system is never able to lock on to the selected track.

In my opinion, there is nothing wrong with the control electronics or the processing side, but that the problem lies either with the motor(s) or with the optics.

When repairing old equipment one of the first things I look at is the electrolytics near heat sources like power transistors. Nearly every TV I have fixed had failed due to a "dried out" cap.

My understanding of electrolytic caps is that they have a mean life expectancy of 10-12 years, which makes capacitors a legitimate concern. Hence, sometimes people just recap an old board without too much investigating. However, I am not convinced it is the capacitors, because the problem seems to by the same for each unit (so then why that same capacitor when these devices are low powered and don't get that hot?).

I have looked on the internet for some clues, but I didn't find anything of substance. It seams most people just throw away their old CD players and buy a new one (I use an MP3 anyway, so please don't suggest buying one as an answer). I could quite easily throw them in the bin and forget about them, but then I would still be left in ignorance about this problem.

My reasoning tends towards the diode or phototransistor having deteriorated over time, so a disk is detected but the system effectively behaves like the CD is scratched or dirty (which is not the case having tried with multiple CDs - obviously).

What is the best way of testing my theory (the diodes), without an oscilloscope? I have some old working CD-ROM drives and could possibly exchange the diodes, but I was wondering if there was a better way, since it may not be the diodes at all, maybe the motor or driver circuit.

What do people think?

.o:0|O|0:o.
P.s. Someone once suggested that the expiry date is built into the system (like the Blade Runner movie), but I think that is unlikely, though technically possible.

Simon:
it is the laser diode. I have been banging on about this for ages. I personally have made a choice to not buy any more CD players because they are deliberately made with weak laser diodes and they fail often after only 3 months. I replaced the cd drive in 2 of my dads HIFI systems, the drive cost half the cost of the whole system and took my up to 2 hours to replace making it unviable. My dad now uses a computer CD drive I rigged up for him plugged into an old amplifier, ok he canot skip tracks back and forward he can only play the whole cd but that is all he needs and the damn thing does not keep breaking,

naturally the fault is those bastard manufacturers in china and yes they are bastards !. if I were the uk government I'd have all cd players examined before allowing import. they bang on about us being green with energy but don't have  problem with millions of electronic devices going to landfill because they were made to fail.

end of rant !

Mechatrommer:
one var resistor need to be tuned to get back to the "tune", the problem is, you need to find which. i'm suspecting some voltage reference has been off calibration value ;)

qno:
Have you tried to clean the laser lens with some alcohol?

Check out the motor wires, sometimes the tiny plugs on the wire cannot handle the startup current of the motor anymore.
If the logic does not get correct data within a few seconds it stops.
If it works after some fumbling on the connector the contacts are burned.

Simon:
cleaning the laser helps in the beginning but after that it is a permanent problem. generally the CD will spin but will not read the CD and will report no disk

Navigation

[0] Message Index

[#] Next page