Troubleshooting CD Players

[bangsezmax]

This uses a KSS-210A laser, which is probably bad. Liberty Electronics on ebay sells good ones. This has a Sony chipset but the microprocessor is different and the behavior is probably due to that. Normally if it achieves focus lock it will spin the disc, for at least a couple seconds while it reads the TOC. If it can't read TOC because the laser power is low it will stop spinning. Never saw a player that turns 1/4 turn and stops. You can try giving the disc a little push and see if it spins more. If so, the disc motor is bad. If not, the laser is probably bad.

Nakamichi CD Player 4 -- spins briefly but won't read TOC (except sometimes when I help it)

A Nak CD Player 4 just came in my shop as a donation. Like others have said here, loading the CD it will spin briefly -- not even a full revolution -- and stop. No sizzling noise, it just never gets to the TOC. On the display, it will say "Disc" for several seconds (so it's detecting that there is a disc) while the laser clicks trying to search. But the disc isn't spinning so there's nothing for the laser to find.

Seeing @dr*audio say above, "You can try giving the disc a little push and see if it spins more," I did that and lo and behold it read the TOC. When I pressed play, it played the disc. I tried repeating the process and it is very intermittent. If I spin the disc manually, it'll load the TOC about once out of every 20 times. But when it does load, it plays the disc with no issues. I can search, etc, and it's all good so long as the TOC gets read.

If the transport plays through the disc just fine once it reads the TOC, we can assume there's not a problem with the motor, right? If it sometimes manage to read the TOC and will play the disc, we can assume there's not a problem with the laser, right?

So what the heck is going on?

Reading through this and other threads, it appears that people who replaced the transports had the same issues as they did before. Or at least, nobody has reported that putting in a replacement transport fixes the issue.

 

[eiraved]

I would guess the motor has the issue, as per dr*audio's instructions.

 

[bangsezmax]

I would guess the motor has the issue, as per dr*audio's instructions.

But then why would it be able to play the disc once the TOC is read? It's the same motor.

 

[eiraved]

But then why would it be able to play the disc once the TOC is read? It's the same motor.

It's possible both the motor and the laser have issues.

 

[bangsezmax]

After letting it play for a while and warming up, the motor is getting more responsive. It actually read the TOC without help once.

 

[dr*audio]

After letting it play for a while and warming up, the motor is getting more responsive. It actually read the TOC without help once.

Since you have it where you can get it to play, connect your scope up to the RF test point and look at the eye pattern. If it's less than 1V P-P, the laser is bad. If it's less than 1.5V p-p, you can try adjusting the laser power to bring it up to 1.5V. Then play an entire CD, monitoring the RF test point. If it drops off, the laser is bad. On a customer unit, if the laser power is low I replace the laser.

 

[bangsezmax]

Since you have it where you can get it to play, connect your scope up to the RF test point and look at the eye pattern. If it's less than 1V P-P, the laser is bad. If it's less than 1.5V p-p, you can try adjusting the laser power to bring it up to 1.5V. Then play an entire CD, monitoring the RF test point. If it drops off, the laser is bad. On a customer unit, if the laser power is low I replace the laser.

On this unit, you actually need another separate physical device for testing, part # DA09155A. I don't have one.

Not that it matters, because I am of the opinion that this issue is (at least partially) mechanical in nature.

Since I was able to get the TOC to load sometime by manually spinning the disc, it occurred to me that the issue might be related to the spindle platter not properly gripping the disc. So as a test, I took some adhesive tape and manually created some tackiness on the spindle platter by pressing the tape down on it and then removing it. Huge improvement. TOC will read about 80% of the time. I'm feeling like if there was sufficient grip/tack on that platter, it would work properly at least most of the time.

Now to figure out how to do that without adding a layer of something that will vertically alter the position of the CD.

 

[eiraved]

On this unit, you actually need another separate physical device for testing, part # DA09155A. I don't have one.

Not that it matters, because I am of the opinion that this issue is (at least partially) mechanical in nature.

Since I was able to get the TOC to load sometime by manually spinning the disc, it occurred to me that the issue might be related to the spindle platter not properly gripping the disc. So as a test, I took some adhesive tape and manually created some tackiness on the spindle platter by pressing the tape down on it and then removing it. Huge improvement. TOC will read about 80% of the time. I'm feeling like if there was sufficient grip/tack on that platter, it would work properly at least most of the time.

Now to figure out how to do that without adding a layer of something that will vertically alter the position of the CD.

Click on this post.

Troubleshooting CD Players

@rockrink, maybe a long shot, but could need recapping in the motor drive and servo circuits. I've had some early Technics players from circa 1984-86, that had bad electrolytics that screwed up the spindle motor running smoothly (or at correct speed), thereby throwing off the ability to read a...

audiokarma.org

 

[bangsezmax]

So check out this spindle platter --

Surface 1 is metal and rather slick
Surface 2 appears to be plastic (or dried out rubber) and sits below the lip of surface 1
The third part is spring loaded hard plastic.

What exactly is supposed to be gripping the disc? I'm wondering if this is some sort of design flaw with this mechanism. As it ages and gets used, what little grip it had when new has gone away.

What could I do to the metal or hard plastic to increase the grip?

Would it be possible to replace it with different spindle platter (would need to make sure the height is exactly right)?

 

[eiraved]

Are you sure the hard plastic is not just hardened rubber? I would attempt to find a way to restore the rubber as indicated in the link I sent you. It's inexpensive and won't cause additional damage, so why not?

 

[dr*audio]

So check out this spindle platter --

Surface 1 is metal and rather slick
Surface 2 appears to be plastic (or dried out rubber) and sits below the lip of surface 1
The third part is spring loaded hard plastic.

What exactly is supposed to be gripping the disc? I'm wondering if this is some sort of design flaw with this mechanism. As it ages and gets used, what little grip it had when new has gone away.

What could I do to the metal or hard plastic to increase the grip?

Would it be possible to replace it with different spindle platter (would need to make sure the height is exactly right)?


View attachment 3309892

View attachment 3309907

This assembly is very common. The center part just locates and centers the disc. The metal part has a rubberized coating. The magnet in the chick assembly holds the cd to the table.
You don't need the other assembly to test it. Ignore that instruction. Simply connect your scope to the RF test point, hit play and measure the eye pattern.

 

[bangsezmax]

Since you have it where you can get it to play, connect your scope up to the RF test point and look at the eye pattern. If it's less than 1V P-P, the laser is bad. If it's less than 1.5V p-p, you can try adjusting the laser power to bring it up to 1.5V.

It was reading 1.04 v pk to pk.

I adjusted the trimpot on the transport and it was showing 1.52 v with the occasional bump up to 1.60 v. And it was loading everything I throw in it.

Then play an entire CD, monitoring the RF test point. If it drops off, the laser is bad. On a customer unit, if the laser power is low I replace the laser.

After a few minutes, it's bouncing between 1.28 v and 1.36 v.

How difficult is it to replace the laser? (NM -- found a video).

 

[Ullar]

Hello good people!

Really need you help here. I'm having a trouble with one of my Technics SL-P1300 players. Both of them were sourced from Japan in "not working" condition. Got one of them working after replacing two small transistor looking "fuses" and recapping the main board and motor board. The other one still lays open on my working table.

The symptoms are:
1) Player powers up. Display lights up like normal.
2) With no disk i can see pick-up moving to center and trying to focus. There is visible red light from the laser.
3) After putting the disk on it spins up and keeps rotating endlessly, no TOC read.
4) There is some repeating noise, like a hiss.
5) RF signal looks disturbed. Like starting to form and then breaking apart immediately. Look at the linked image.
RF_signal

What I have done/tried already:
1) Cleaned and oiled the rails and motor axle.
2) Cleaned the laser lens
3) Recapped the main board containing power, digital control and servo circuits.
3) Recapped the motor board, just in case.
4) Tested power lines for voltage and ripple with an oscilloscope.
5) Tried to fine tune best eye, focus offset and tracking balance/offset pots.
6) Swapped the laser from the working SL-P110.
7) Adjusted the height of the platter as per manual.
8) Same symptoms.

I recall seeing some posts somewhere discussing the specific problems of SL-P1200/SL-P1300 that were solved with replacing a certain IC. Unfortunately I can't find those postings any more. If anybody can direct me in the right direction with that, it'll be greatly appreciated too.

 

[dr*audio]

It was reading 1.04 v pk to pk.

I adjusted the trimpot on the transport and it was showing 1.52 v with the occasional bump up to 1.60 v. And it was loading everything I throw in it.



After a few minutes, it's bouncing between 1.28 v and 1.36 v.

How difficult is it to replace the laser? (NM -- found a video).

So Liberty electronics on ebay sells good lasers that they source in China. I've used them, they seem to last and work well. I had one dud and they replaced it immediately. I wouldn't buy from anyone else.

 

[dr*audio]

Hello good people!

Really need you help here. I'm having a trouble with one of my Technics SL-P1300 players. Both of them were sourced from Japan in "not working" condition. Got one of them working after replacing two small transistor looking "fuses" and recapping the main board and motor board. The other one still lays open on my working table.

The symptoms are:
1) Player powers up. Display lights up like normal.
2) With no disk i can see pick-up moving to center and trying to focus. There is visible red light from the laser.
3) After putting the disk on it spins up and keeps rotating endlessly, no TOC read.
4) There is some repeating noise, like a hiss.
5) RF signal looks disturbed. Like starting to form and then breaking apart immediately. Look at the linked image.
RF_signal

What I have done/tried already:
1) Cleaned and oiled the rails and motor axle.
2) Cleaned the laser lens
3) Recapped the main board containing power, digital control and servo circuits.
3) Recapped the motor board, just in case.
4) Tested power lines for voltage and ripple with an oscilloscope.
5) Tried to fine tune best eye, focus offset and tracking balance/offset pots.
6) Swapped the laser from the working SL-P110.
7) Adjusted the height of the platter as per manual.
8) Same symptoms.

I recall seeing some posts somewhere discussing the specific problems of SL-P1200/SL-P1300 that were solved with replacing a certain IC. Unfortunately I can't find those postings any more. If anybody can direct me in the right direction with that, it'll be greatly appreciated too.

RF signal should have more "waves" in the waveform. Look at the one from the working player and you'll see what I mean. Technics players have lower amplitude in the rf waveform. I think 800mV is ok. I'll try to have a look at the service manual and give you some test points to look at. I've never seen one with this problem. I'm guessing:
1. Maybe isn't getting focus lock.
2. Maybe tracking lock.
3. On one of these older Technics players I've seen the transistors that drive the sled, or motor or tracking / focus coils have low HFE. You can look at the FE, TE and Sled signals and see if there is a high amplitude signal, like maybe 1.5V p-p, (meaning a lot of correction happening) and then look at the outputs that go to the coils in the laser and the motors and see if the signal is much lower. If any have lower signal on the output I'd suspect the transistors.

 

[Ullar]

RF signal should have more "waves" in the waveform. Look at the one from the working player and you'll see what I mean. Technics players have lower amplitude in the rf waveform. I think 800mV is ok. I'll try to have a look at the service manual and give you some test points to look at. I've never seen one with this problem. I'm guessing:
1. Maybe isn't getting focus lock.
2. Maybe tracking lock.
3. On one of these older Technics players I've seen the transistors that drive the sled, or motor or tracking / focus coils have low HFE. You can look at the FE, TE and Sled signals and see if there is a high amplitude signal, like maybe 1.5V p-p, (meaning a lot of correction happening) and then look at the outputs that go to the coils in the laser and the motors and see if the signal is much lower. If any have lower signal on the output I'd suspect the transistors.

Thank you dr*audio for looking into my problem! Very much appreciated.

1. I looked at the FLOCK voltage on System Control IC. It lowers immediately after start-up from 4.9Vpp to 0.1Vpp (should be 0V for Play according to manual). Then it has some fluctuations, but generally very close to 0V.
2. I don't know how to check that but the more I think about it the more it looks to me that for some reason it cant find or recognize TOC and keeps searching for it over and over again.
3. FE (FEOUT) and TE (TEOUT) signals at Optical Servo Control IC are fluctuating around 0.4 to 0.8 Vpp. There is al lot of fluctuation so it's diffcult to get more definite readings. I don't know where to measure Sled signal. I also checked the coil voltages going into laser. There is a lot of activity and fluctuation with voltages about 2Vpp for focus and 5Vpp for tracking coil. Should be 2Vpp during Play according to manual. There appears to be quite a lot of positive bias on Sled (TRV) coil (fluctuating around +5V mean). Manual says 0.1V. Should I check transistors in that circuit? Q181/181 on attached schematics?
SL-P1300 laser coil drivers

 

[dr*audio]

Thank you dr*audio for looking into my problem! Very much appreciated.

1. I looked at the FLOCK voltage on System Control IC. It lowers immediately after start-up from 4.9Vpp to 0.1Vpp (should be 0V for Play according to manual). Then it has some fluctuations, but generally very close to 0V.
2. I don't know how to check that but the more I think about it the more it looks to me that for some reason it cant find or recognize TOC and keeps searching for it over and over again.
3. FE (FEOUT) and TE (TEOUT) signals at Optical Servo Control IC are fluctuating around 0.4 to 0.8 Vpp. There is al lot of fluctuation so it's diffcult to get more definite readings. I don't know where to measure Sled signal. I also checked the coil voltages going into laser. There is a lot of activity and fluctuation with voltages about 2Vpp for focus and 5Vpp for tracking coil. Should be 2Vpp during Play according to manual. There appears to be quite a lot of positive bias on Sled (TRV) coil (fluctuating around +5V mean). Manual says 0.1V. Should I check transistors in that circuit? Q181/181 on attached schematics?
SL-P1300 laser coil drivers

I think you're on to something in the Sled Servo, but if there is that much offset, the sled should be slammed up against one end or the other. Is it? If not, move the sled to the position furthest from the disc table with the player off, then turn the player on with no disc in it. Did the sled go to the disc table end? If not, ohm out the coil for the sled.

 

[Ullar]

I think you're on to something in the Sled Servo, but if there is that much offset, the sled should be slammed up against one end or the other. Is it? If not, move the sled to the position furthest from the disc table with the player off, then turn the player on with no disc in it. Did the sled go to the disc table end? If not, ohm out the coil for the sled.

Yes, If I move the sled furthest out from the center and switch on the player with no disc, it moves back to the center and tries to focus.
The bias on Sled drive is not constant but jumps around quite a lot. I made a video:
Voltage on sled drive

 

[dr*audio]

Yes, If I move the sled furthest out from the center and switch on the player with no disc, it moves back to the center and tries to focus.
The bias on Sled drive is not constant but jumps around quite a lot. I made a video:
Voltage on sled drive

Before going further, this unit has a position locater, which is a variable resistor attached to the sled motor and moves with it. Try putting a bit of Deoxit on it and slide it back and forth a bunch of times. See if that helps. It's #12 in the picture below:

 

[deckblad]

Greeting​

Thank you, Dr, for being a steadfast contributor to the resurrection of many a fine CD player. I've got a new one for you, if you please.

Context​

This Sony CDP-C35 is very susceptible to skipping from light taps on the table or from tonal vibrations. TOC loading, seeking, playing are good if not disturbed at all. Track seeking takes about 3 seconds. I've verified the top arm yoke is not contacting. I can wiggle it with the whole CD tray while playing and get no rubbing or skipping. Pickup springs have been re-stretched and suspension feels sturdy yet compliant. Lens looks clean. Spindle motor top bearing lubricated. All transport mechs clean and lubricated. I can hear a lil repeating noise from what I think is the tracking or focus motors, once per revolution of the CD. The motor itself seems quiet when it first spins up or down.

I'm very very new to using an oscilloscope so don't assume I'm measuring things correctly here. I totally understand that teaching OSC operations is outside the scope of this thread.

RF​

RF measurement looks messed up. Do I need to set a trigger mode on the OSC to properly see the diamond pattern or is this simply not right? There's nothing in the manual to suggest how to calibrate this.

Focus​

I'm pretty sure I have focus set properly to ~100mV center. But, am seeing conflicting info in the svc manual.



In the manual I see this
... and this

First graph is centered on 100mV with a 200mV p-p. Second graph is centerd on 0V with a 500mV p-p? What is correct? Why are these different?

Tracking​

I don't think tracking is correct. The screenshot in the svc manual is hard to interpret. I think the manual wants to see a 2v p-p amplitude with a 0v center? Best I can get is about 700mV top to bottom.



Again the two sections of the svc contradict each other (unless they mean different things I don't understand yet)

My interpretation of the first image shows 0V center with ~2V p-p? Second graph shows 0V center with 100mV p-p?

Thanks​

Thank you for your time!