Troubleshooting CD Players
- Thread starter dr*audio
- Start date
dr*audio
Fish fingers and custard!
What is the input set to; mV/div?
dr*audio
Fish fingers and custard!
RF looks good, a little low but it might be the disc. I want to see the TE testpoint. 2mS/div.
classyharlan
Active Member
50mv
classyharlan
Active Member
classyharlan
Active Member
TEI (pic 1) and TEO, 2mS/div
dr*audio
Fish fingers and custard!
Those look really good. I am not sure why it fails at the outer tracks. Try monitoring the RF and see what it looks like when it's going from the last track it will play to the one it won't play. If the peak to peak falls below 1V, then the laser power is a bit low.
classyharlan
Active Member
The below video is 3 discs on after the other, putting each in the tray and pushing play. Disc 1 is good, the others fail; discs 1 and 3 are 45 minutes, disc 2 is 79 minutes.
Regarding laser strength, is it correct that it doesn't matter what waveform the scope is showing, as long as that waveform is around 1V in height then it's ok?
So for the other deck (Panasonic) that I'm also currently asking about, it just spins and doesn't play so the pattern it shows isn't an eye pattern, but since the height is only 0.1V then that is an indicator that the laser is near dead?
Likewise for the deck in this video, since the waveform height is about 1V even when it fails then that means that the problem is not with the laser?
On a deck with a completely dead laser, will there be no output?
On my deck with the weak laser, since it's on its way out anyway, is there any value in looking at the rf and increasing the laser power?
Regarding laser strength, is it correct that it doesn't matter what waveform the scope is showing, as long as that waveform is around 1V in height then it's ok?
So for the other deck (Panasonic) that I'm also currently asking about, it just spins and doesn't play so the pattern it shows isn't an eye pattern, but since the height is only 0.1V then that is an indicator that the laser is near dead?
Likewise for the deck in this video, since the waveform height is about 1V even when it fails then that means that the problem is not with the laser?
On a deck with a completely dead laser, will there be no output?
On my deck with the weak laser, since it's on its way out anyway, is there any value in looking at the rf and increasing the laser power?
dr*audio
Fish fingers and custard!
Lets just deal with the Denon for now. Can you find out what is making that click, click click sound before it fails? That's a clue. The rf looks ok.
classyharlan
Active Member
It's the gear slipping as the sled tries to move in beyond the home position.
dr*audio
Fish fingers and custard!
Clean the home switch or check it with your meter on ohms.
classyharlan
Active Member
I cleaned the leaves of the home leaf switch with deoxit on a qtip. The meter reading seemed ok both before and after cleaning. The bad discs from yesterday will today play from track 1.
One failing disc from yesterday did not today have problems playing. The other failing disc (the longer one) is failing today when selecting tracks in the middle and beyond. It first moves the sled out to the track. Then it either 1) sticks on the track spinning without starting, or 2) the sled moves back to home and either a) stops, or b) stops and respins, or c) tries going past home, or d) any number or other things that I can't remember well enough to describe in detail.
When it goes back home it either does so e x t r e m e l y s l o w l y taking maybe a minute, or at the normal speed--like after stop is pressed--but with intermittent jerky motions.
I tested some other previously failing discs and they still failed today. I also found one other 75+ minute disc that failed and that I hadn't tested before. I also found multiple other 75+ minute discs that didn't fail and that I hadn't tested before.
I don't think there are currently any normal length or shorter discs that are not failing, it's only failing on longer discs. The failing normal length disc from yesterday was today ok.
One failing disc from yesterday did not today have problems playing. The other failing disc (the longer one) is failing today when selecting tracks in the middle and beyond. It first moves the sled out to the track. Then it either 1) sticks on the track spinning without starting, or 2) the sled moves back to home and either a) stops, or b) stops and respins, or c) tries going past home, or d) any number or other things that I can't remember well enough to describe in detail.
When it goes back home it either does so e x t r e m e l y s l o w l y taking maybe a minute, or at the normal speed--like after stop is pressed--but with intermittent jerky motions.
I tested some other previously failing discs and they still failed today. I also found one other 75+ minute disc that failed and that I hadn't tested before. I also found multiple other 75+ minute discs that didn't fail and that I hadn't tested before.
I don't think there are currently any normal length or shorter discs that are not failing, it's only failing on longer discs. The failing normal length disc from yesterday was today ok.
dr*audio
Fish fingers and custard!
It is very unusual for a player to have so many peculiar behaviors when failing. It almost sounds like the microprocessor is bad. If so, the part is not going to be available. The other possibility is the Sony servo processor IC, which is also no longer available from any reputable supplier.
By any chance, are the CDs that fail scratched?
By any chance, are the CDs that fail scratched?
classyharlan
Active Member
The discs aren't scratched. They also play without problem in other decks.
Is there any way for a novice to check the microprocessors?
dr*audio
Fish fingers and custard!
Not directly. We check the other systems and if everything else is working correctly but the player acts like it has brain damage, you can assume it's the microprocessor. Check the power supply for the microprocessor (Vdd) with your scope. It should be 5V with less than 100mV of ripple.
dr*audio
Fish fingers and custard!
The other thing to do is try to figure out what the difference is between the discs that play and those that don't, and monitor the rf, the tracking error and focus error while it plays the last track it can play correctly, with the scope, and see what happens when it tries to play the next track. Don't skip ahead, just play the last good track normally and let the player advance by itself. This is what I would do if I had the player in front of me. Hard to do it by remote control. When looking at the tracking error and focus error, put the scope on DC coupled, so that if the voltage starts to climb (more error) you will see it.
classyharlan
Active Member
It looks like the rf height differs by .2V between good and bad discs (1V for good and .8V for bad). However there are no other commonalities between all the bad discs or between all the good discs.
The TE and FE seem the same for all discs, except when there's failure in which case the heights of both TE and FE go through the roof.
dr*audio
Fish fingers and custard!
What I would suggest first is to find an older prerecorded CD, from the 1980's or 1990's to use as a benchmark, because older CDs have higher reflectivity. Use that CD to adjust the laser output so the rf is 1.5V peak to peak. Now play the problem CDs and see if they play. I use a Sony test CD, but I doubt you'll find one of those.
classyharlan
Active Member
Does the test disc have a formal product name or something like that that might be searchable?
I had bought one long ago (from Sony Parts Division). Here's a picture of it.
Sony YEDS 18
Ebay.ca has one for $137 US
Ebay.com has one for $138
I think I paid $25 in 1988 or 89
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