CD player with distortion. laser?

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#61
Mooly said:
Tilt test showed nothing then... had to be done.

This sounds odd too... you see that coil with a ferrite core (do not attempt to turn it.

With CD playing if you "finger" the underside of the coil pressing your finger onto the area around it, does the audio improve ?

What that does is alter the tuning of the coil, again may or may not prove something. If the player throws a wobler just switch off and on again.
Click to expand...

you are going to think me a right novice, which picture is that on? (the coil)
 
#69
Mooly said:
Think you are going to have to try it on the external DAC if poss as that splits the player in half. See what that proves.
Click to expand...

I want to repeat this as it's a very good point, not just in this case, but for all troubleshooting.

My uncle Bill spent over 40 years at the same factory as lead electronics tech. His approach when troubleshooting something where he didn't suspect a specific problem was: "I start in the middle of the schematic and test. Then I know whether to work upstream or downstream. Saves a lot of time."

I like the approach because it quickly shows you which half of the circuit the problem may be in. Of course if it's a problem you've seen before, or similar, you'd go right to that part. But if you don't know, this works well.
 
#70
Darn it, not the PSU caps, although I could not replace one as they didnt have it, doubt it would be that simple to be the one I couldn't replace.
Its a shame that I cannot get the sound on here so that you can listen to it.

So its not the laser assembly or control area, DAC not the PSU caps or regulators.
Like my Dad said, really need a scope to see what its doing.

Still determined to get it fixed.
 
#74
all the music is there in the background, its like someone has stuck a much louder fluttering modulating sound over the top of it as well, that runs with the track, so if there is a quiet part the 'distortion' is quieter as well.
So its picking up the complete signal from the disc, but adding something else to it, that is what it seems like, could it be something I have overlooked, faulty connections, or is that unlikely.
 
#75
zottinger said:
Where did my reply go?
Probably won't be of much help, but the symptoms sound awfully similar to the issues I have with a Toshiba CD player, also based on cdm4/tda1541a.
Since the problems with my player started after I took it apart to fix a broken rca socket my guess was the problem being a faulty connection of the data cable from the laser assembly to the pcb, since it was a pain to get it back in with the cable being really short and the connection placed under the transport.
So it might be worth a shot to check all the connections. I didn't get around redoing the connections yet, cause frankly I'm not really motivated to go through the annoying process of fiddling the cable in under the transport without being sure if that will solve my problem.
So I'm really interested if you're able to find the root of the problem cause it sounds like we're having the same issue.
daniel
Click to expand...

I am curious, as you say that you are getting a similar sound issue after you had the unit apart?
So it was working fine before hand, and since you have removed and reinstalled the cable you get the same modulating sound laced over the main track that is playing, is that true?
 
#76
So it's front end related.

As you haven't a 'scope I think it's well worth confirming the laser current if you can find the appropriate test points and method.

I know they are weird things I keep suggesting 🙂 but again a low output will cause this type of effect. You've replaced the laser itself... that doesn't mean there's not a problem though. The transistor that feeds the laser has been known to fail before now.

If you do measure I would recommend first soldering wires to the test points and securely connecting the meter first... poking around with it on could spell disaster either by an inadvertent short or just "spiking" the laser.
 
#77
Ah, so this transistor that feeds the laser might not be feeding the correct voltage, makes sense to me.
Would it more than likely just be one feeding the laser.
I take it that I can find the correct current that it needs to be supplying the laser from the philips service manual?
 
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