How strange you may say? Well strange as it seems I have tried about 10 other CD's and not one of them will play other than the player giving me a "Mash" of noises as the laser tries to read them and that CD turns out to be YES 90125.
I got this Technics SL-PC33 for free because it was declared unfixable... in other words the CD mechanism is strange unabtanium. The first thing that I found was that the spindle motor was very noisy, so I rebuilt it and it runs much better but I managed to source some new ones that look identical, so that was problem one that I think is solved.
So now here is my question, why would it read only ONE CD out of like 10?
I notice there are 6 pots on the mech board... can these help me at all?
Any help or ideas are greatly appreciated! 😀
I got this Technics SL-PC33 for free because it was declared unfixable... in other words the CD mechanism is strange unabtanium. The first thing that I found was that the spindle motor was very noisy, so I rebuilt it and it runs much better but I managed to source some new ones that look identical, so that was problem one that I think is solved.
So now here is my question, why would it read only ONE CD out of like 10?
I notice there are 6 pots on the mech board... can these help me at all?
Any help or ideas are greatly appreciated! 😀
Perhaps the one CD it does play is actually one that is defective or at the limit of some tolerance (seriously).
Have you used a 'scope and looked at the RF signal. Without a scope and you are just stumbling blindly along. You need to see what the RF looks like on the disc it does play.
Have you used a 'scope and looked at the RF signal. Without a scope and you are just stumbling blindly along. You need to see what the RF looks like on the disc it does play.
I once had a SHARP cd player that would only play my Eric Clapton cds and no others!!!!
No amount of adjustments would solve the problem.
Andy
No amount of adjustments would solve the problem.
Andy
Playing only one disc usually means that the laser pickup is rooted.
Disc turntable height is critical, you need to be sure that it is correct.
mark the positions of the trimpots before you touch any of them.
Better still, get hold of a service manual.
IIRC, that mech has a very small belt that drives the sled worm screw...these stretch and slip but probably not the cause of fault.
Dan.
Disc turntable height is critical, you need to be sure that it is correct.
mark the positions of the trimpots before you touch any of them.
Better still, get hold of a service manual.
IIRC, that mech has a very small belt that drives the sled worm screw...these stretch and slip but probably not the cause of fault.
Dan.
Technics CD players have relatively narrow tolerance of what I would call "field of operation" (disc surface reflectivity, pit definition, focus and tracking). As they age, their tolerance gets even narrower. Your player simply likes your disc (I think it got an an abnormal height offset in the production process) and so the player manages to read it out. This could be a direction in which to work: to adjust the spindle height. I doubt the laser is dying because the reading would fail towards the outer edge of disc. Get the service manual and try the adjustment procedure.
Thanks guys! I will have to try to track down a service manual and continue adjusting the spindle clamp height, since I did not keep track of it exactly but I did try to get it so that the CD was as close to the laser as possible, maybe it is too close.
There is also still a fair amount of motor vibration and noise (not nearly as bad as it was), luckily I found a source for new motors and have a handful on the way.
The CD tray moves by means of an electro-magnet on a shaft and movement is determined by a wiper on a plastic film resistor rather than a worm drive with a motor... very unusual... not sure how reliable this is but if it works than whatever.
I do have a scope, never thought of looking at the RF signal, how would I go about this and what should I see?
There is also still a fair amount of motor vibration and noise (not nearly as bad as it was), luckily I found a source for new motors and have a handful on the way.
The CD tray moves by means of an electro-magnet on a shaft and movement is determined by a wiper on a plastic film resistor rather than a worm drive with a motor... very unusual... not sure how reliable this is but if it works than whatever.
I do have a scope, never thought of looking at the RF signal, how would I go about this and what should I see?
The RF should look like in this post,
http://www.diyaudio.com/forums/digital-source/226288-sony-cdp790-kss240-restoration-project.html
It should be as steady and clearly defined as in the picture. The amplitude is typically around 1.2 to 1.5 volts pk/pk for a majority of players. You should be able to pick the RF up without a manual, it may even be marked. If you get stuck then look up the data sheet for the chipset used and locate it that way.
The spindle motor should have no detectable vibration or noise. That is definitely something to look at and work on.
http://www.diyaudio.com/forums/digital-source/226288-sony-cdp790-kss240-restoration-project.html
It should be as steady and clearly defined as in the picture. The amplitude is typically around 1.2 to 1.5 volts pk/pk for a majority of players. You should be able to pick the RF up without a manual, it may even be marked. If you get stuck then look up the data sheet for the chipset used and locate it that way.
The spindle motor should have no detectable vibration or noise. That is definitely something to look at and work on.
Thanks Mooly! That is a very useful in depth guide, and once again I have learned some new tips and tricks.
I can't disagree with you in the sonic quality aspects of the album, the music itself I like but not my favorite album by them... it is disappointing in the aspect that I cannot get a good feel for how this player compares to my modded CA Azure 640C... probably not good, but then again I have yet to come across a 5 disc changer I actually like.
Yes 90125 is horrible, both musically and sonically
I can't disagree with you in the sonic quality aspects of the album, the music itself I like but not my favorite album by them... it is disappointing in the aspect that I cannot get a good feel for how this player compares to my modded CA Azure 640C... probably not good, but then again I have yet to come across a 5 disc changer I actually like.
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