dr*audio
Fish fingers and custard!
After 72 minutes, if you remove the CD and put it immediately back in, will it play?
Troubleshooting CD Players
- Thread starter dr*audio
- Start date
classyharlan
Active Member
To make sure I'm clear, I meant to say at the point on the disc where 72 minutes would have passed, not that the player has actually run for 72 minutes. (though I imagine the error would be the same in the latter case as well)
For example the 72 minute on a particular disc is at 5 minutes of track 16, if I go to that track then fast forward to 4:50 it will fail when getting to 5 minutes. It will also fail when going directly to tracks 17 and later.
After failure and immediate opening and reclosing the tray, it still fails after the 72 minute mark.
For example the 72 minute on a particular disc is at 5 minutes of track 16, if I go to that track then fast forward to 4:50 it will fail when getting to 5 minutes. It will also fail when going directly to tracks 17 and later.
After failure and immediate opening and reclosing the tray, it still fails after the 72 minute mark.
dr*audio
Fish fingers and custard!
This rules out a failing laser, with the power falling off over time.
Next, play a CD and probe the laser connecting cable with a plastic pen, flexing them a bit. See if the player stops working. Sometimes the wires or flat flexible cable break. If it works ok:
Clean the metal posts that the laser slides on with alcohol until nothing comes off. Allow to dry and then put 3 drops of light machine oil on the slides on both sides of the laser, then move the laser back and forth by hand to spread it around. Then test at the 72 minute mark. If it fails:
Connect a DMM or scope to the sled motor terminals, put it in play and observe the voltage. The voltage should slowly climb up to some voltage, then the sled moves and the voltage will drop to 0V or even negative, then start over. The max positive voltage should not be much above 1V. If it consistently goes above 1V, move to the 72 minute mark, put it in play and see if the voltage goes higher still. If so, there is either excessive friction in the sled, a bad tooth on a gear (or a split worm gear) or the motor could be bad (less likely.)
dr*audio
Fish fingers and custard!
If you remove gear #15 it will free up the sled and you can check to make sure it isn't binding. The laser should move back and forth by itself if you tilt the mechanism with the gear removed. Note that there is a worm gear on the motor. Check it carefully to see if it is cracked.
classyharlan
Active Member
Probing the cables did not cause failure. Before cleaning the rails I connected a multimeter to the sled motor and observed that the voltage increase and decrease did not exceed 1V at any time. I removed gear 15 to make cleaning the rails easier, verified that the sled moved freely back and forth, and then cleaned the rails as suggested.
After reassembly, the test disc exhibited the same behavior of failing at 72 minutes, and then a host of other errors started happening--not sure if I caused the new errors with disassembly or if I just missed them initially:
- sled motor trying to move in past the home position on reading or starting to play a disc (click click click from the gear #15 trying to rotate in the wrong direction and slipping)
- spinning in reverse on startup
- skipping on search fast forward/reverse
- occasional skipping on play
- crackling on playback, ie digital conversion errors (?)
Seems to consistently affect CDs over 40 minutes, shorter CDs are more likely to be ok. After letting the deck sit for a couple hours, testing now with 3 shorter CDs (35 minutes, 40, and 16) in a row there have been no errors. Earlier two of these discs had errors when played after a longer CD that also had errors.
After reassembly, the test disc exhibited the same behavior of failing at 72 minutes, and then a host of other errors started happening--not sure if I caused the new errors with disassembly or if I just missed them initially:
- sled motor trying to move in past the home position on reading or starting to play a disc (click click click from the gear #15 trying to rotate in the wrong direction and slipping)
- spinning in reverse on startup
- skipping on search fast forward/reverse
- occasional skipping on play
- crackling on playback, ie digital conversion errors (?)
Seems to consistently affect CDs over 40 minutes, shorter CDs are more likely to be ok. After letting the deck sit for a couple hours, testing now with 3 shorter CDs (35 minutes, 40, and 16) in a row there have been no errors. Earlier two of these discs had errors when played after a longer CD that also had errors.
Last edited:
classyharlan
Active Member
Yes I do.
dr*audio
Fish fingers and custard!
Get the service manual and perform the Focus Bias (or Focus Offset) and Tracking Offset adjustments.
Also, look at the rf waveform and let me know what the peak to peak voltage is.
classyharlan
Active Member
Thank you for suggesting the offset adjustments. I did the tracking offset but wasn't able to figure out how to get an rf waveform for the focus offset as the service manual calls for (instead of a waveform I could only see fuzz on the scope) so out of frustration I just randomly turned the focus offset resistor. Turning one way caused playback to stop so I turned it the other way. After that I tested 10 discs 75+ minutes each by playing the final track and one disc failed but the rest were ok so I'm going to call that fixed. I wish I could have fixed it the proper way instead of just getting lucky but you take what you can get.
dr*audio
Fish fingers and custard!
You need a scope with minimum 60MHz bandwidth. If yours has the required bandwidth you simply need to adjust the horizontal sweep until you can see the eye pattern. You need to connect the probe to the rf test point and ground. I think the scope needs to be set to 2uS/div.
classyharlan
Active Member
My scope is 250MHz, I must have misread the manual and not found the correct test point. (The manual was in German so maybe I get a pass on that.)
classyharlan
Active Member
Although a lot better and most discs are ok, the deck is still failing on too many.
I was able to get an eye pattern. It is very shaky. If I turn the focus offset resistor I can make the pattern blurrier but no matter how I turn the resistor I can't get the pattern stable and in good focus.
Peak to peak depends on the disc and goes from 100V to 150V.
I was able to get an eye pattern. It is very shaky. If I turn the focus offset resistor I can make the pattern blurrier but no matter how I turn the resistor I can't get the pattern stable and in good focus.
Peak to peak depends on the disc and goes from 100V to 150V.
dr*audio
Fish fingers and custard!
Supposed to be 1V to 1.5V. Check your scope settings an use a 10X probe.
When you oiled the top bearing of the disc motor, did you actually see the oil on the bearing? It sound like you oiled the wrong thing or not at all. The disc motor is the one that spins the CD. The disc table sits on top of the shaft. The bearing is at the bottom of the shaft.
classyharlan
Active Member
I miscalculated the height, the scope was set to 50V/div and the waveform height was 10 to 15 divisions depending on the disc.
No. I touched the syringe on the point where the shaft enters the motor body and then I spun the table and pulled it up and down to work the oil in. I'll do it again (this will be the third time).
No. I touched the syringe on the point where the shaft enters the motor body and then I spun the table and pulled it up and down to work the oil in. I'll do it again (this will be the third time).
classyharlan
Active Member
Panasonic SL-PS700
Insert a disc and it spins indefinitely. Doesn't react to any key pushes except tray open.
On power up or inserting a disc the lens jumps a couple times, not the normal controlled up and down, just a couple quick jumps. It doesn't jump or otherwise move while the disc is spinning.
There is some rhythmic whirring sound that sounds like when a disc is starting up or skipping to a track. I don't know what part that sound is coming from.
For the case of spinning but not reading TOC, the service manual says to check a certain pin, but the pin is on a board on the bottom of the transport which is inaccessible during playback.
https://www.vintageshifi.com/repert....php?pdf=Technics-SLPS-700-Service-Manual.pdf
Insert a disc and it spins indefinitely. Doesn't react to any key pushes except tray open.
On power up or inserting a disc the lens jumps a couple times, not the normal controlled up and down, just a couple quick jumps. It doesn't jump or otherwise move while the disc is spinning.
There is some rhythmic whirring sound that sounds like when a disc is starting up or skipping to a track. I don't know what part that sound is coming from.
For the case of spinning but not reading TOC, the service manual says to check a certain pin, but the pin is on a board on the bottom of the transport which is inaccessible during playback.
https://www.vintageshifi.com/repert....php?pdf=Technics-SLPS-700-Service-Manual.pdf
classyharlan
Active Member
Denon DCD-910
Out of 40 CDs it fails on 6, those 6 CDs fail at the same points consistently (different point for each disc), however other CDs do not fail at those same time points.
On searching to a failing track the sled moves out to the track then moves back to home and continues to try to go past home. It also does this when it gets to a failure point during playback (hits the point then moves back home and tries continuing past home).
Yes. I watched as I put two visibly sized drops of sewing machine oil directly on the bearing.
Videos of the failure on 2 discs, the first fails at around 65 minutes of a 75+ minute disc, the second fails at around 12 minutes of a 45 minute disc.
Out of 40 CDs it fails on 6, those 6 CDs fail at the same points consistently (different point for each disc), however other CDs do not fail at those same time points.
On searching to a failing track the sled moves out to the track then moves back to home and continues to try to go past home. It also does this when it gets to a failure point during playback (hits the point then moves back home and tries continuing past home).
Yes. I watched as I put two visibly sized drops of sewing machine oil directly on the bearing.
Videos of the failure on 2 discs, the first fails at around 65 minutes of a 75+ minute disc, the second fails at around 12 minutes of a 45 minute disc.
dr*audio
Fish fingers and custard!
The laser is probably bad. To confirm you need to look at the rf waveform with the scope. You'll have to solder wires on to the test points.
dr*audio
Fish fingers and custard!
Start playing a disc on Track 1. Set your scope to AC coupled input and .5V / div. Set your timebase to 2mS/ Div. Connect to the TE testpoint and ground and post a picture of the display. You must use a 10X probe.
classyharlan
Active Member
2ms was static so I attached two additional time division photos as well. I'm using a 10x passive probe.
Thank you for your continued help.
