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 Post subject: [CLD-D704] Stripped Label killed my player
PostPosted: 29 Apr 2021, 08:07 
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Hi there,

Tonight after finishing Midnight Run I removed the disc and noticed that it only had a label on one side. I thought it was odd, but it was a new (to me) disc, and assumed it arrived like that. I hadn't noticed anything unusual during playback, and it played just fine. In hindsight, I should have investigated further...

I inserted another disc and pressed play. This time the disc span up, stopped, then started spinning super fast. When I removed the disc, along with the disc, I was also presented with the Midnight Run label!

I opened the player and inspected it. There was no visible damage or debris from the stripped label. I inserted a disc again and watched what is happening. The player loads the disc and correctly identifies it as a Laserdisc before lowering the disc as usual. When pressing play, the disc appears to spin up as usual, but it fails to start playing. The disc then stops, before spinning backwards extremely rapidly. Pressing stop causes slows the disc down, but very slowly - almost like the disc is slipping (I replaced the grip tape just a few weeks ago). The player also failed to play a CD (although I'd never tested a CD in it before).

I'm worried that the label may have damaged the laser pickup. Has this happened to anyone before? Any suggestions to diagnose the cause? I'm a software engineer, and do hardware projects in my spare time. I have an oscilloscope and a copy of the service manual.

The player is a Pioneer CLD-D704.

Cheers!


Last edited by deckard on 03 May 2021, 18:49, edited 1 time in total.
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 Post subject: Re: Stripped Label killed my player
PostPosted: 29 Apr 2021, 16:27 
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My guess is that it shouldn't have damaged it, it could have but its lightly further away from the laser.
And if the old label came out with the second disc then it wasn't off center that much to hit the laser.

Hope others can help, but sounds like no matter you will need to open the player and see what is or isn't happening
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 Post subject: Re: Stripped Label killed my player
PostPosted: 29 Apr 2021, 16:36 
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Did the entire label come out?
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 Post subject: Re: Stripped Label killed my player
PostPosted: 29 Apr 2021, 17:05 
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> Hope others can help, but sounds like no matter you will need to open the player and see what is or isn't happening

I'll get it on my bench tonight after work.

> Did the entire label come out?

Yes, the entire label came out, pretty much undamaged (just a bit creased). I'll have to figure out what kind of adhesive to use to stick it back to the disc.

My current guess as to the playback problem is that maybe a speed sensor got damaged. My assumption is that the reverse spinning is actually the motor trying to slow down the disc by applying reverse torque. For whatever reason it can't read the speed, so doesn't detect that it stopped. Is this a possibility?
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 Post subject: Re: Stripped Label killed my player
PostPosted: 29 Apr 2021, 18:40 
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Here are some images of the stripped label:

Attachment:
289E6A69-B191-45B3-9689-059889EB9EA4.jpeg
289E6A69-B191-45B3-9689-059889EB9EA4.jpeg [ 60.98 KiB | Viewed 293 times ]


Attachment:
E16DBD37-2E05-48E3-ACA0-DBC3FA72A637.jpeg
E16DBD37-2E05-48E3-ACA0-DBC3FA72A637.jpeg [ 64.34 KiB | Viewed 293 times ]


Attachment:
3C17489D-F891-495B-9028-CD1516BB055F.jpeg
3C17489D-F891-495B-9028-CD1516BB055F.jpeg [ 53 KiB | Viewed 293 times ]
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 Post subject: Re: Stripped Label killed my player
PostPosted: 29 Apr 2021, 21:08 
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deckard wrote:
> Hope others can help, but sounds like no matter you will need to open the player and see what is or isn't happening

I'll get it on my bench tonight after work.

> Did the entire label come out?

Yes, the entire label came out, pretty much undamaged (just a bit creased). I'll have to figure out what kind of adhesive to use to stick it back to the disc.

My current guess as to the playback problem is that maybe a speed sensor got damaged. My assumption is that the reverse spinning is actually the motor trying to slow down the disc by applying reverse torque. For whatever reason it can't read the speed, so doesn't detect that it stopped. Is this a possibility?


Yeah, I’d expect that. Not because the speed sensor was borked but because the motor only tries so hard to stop a disc and then it just gives up. If it overbrakes and sends it into reverse it may take some time to slow down and actually power off.

I’ve had labels come off a few times, nothing was ever damaged though.
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 Post subject: Re: Stripped Label killed my player
PostPosted: 29 Apr 2021, 21:57 
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Hoping zeta's experience is yours ......

A foreign body in a player is definitely NOT GOOD.

Thanks for posting your snafu !

Cheers
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 Post subject: Re: Stripped Label killed my player
PostPosted: 29 Apr 2021, 23:16 
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I tested the FG signal, and it seems like the spindle speed sensor is working fine.

I uploaded a video of my problem to YouTube. Any advice appreciated!

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 Post subject: Re: Stripped Label killed my player
PostPosted: 30 Apr 2021, 01:24 
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Running in test mode, I’m seeing a noisy RF signal. I’ve never checked it with a known working setup before though. Does this look wrong?

Attachment:
381255B1-C439-4ECB-A367-63ED7D479806.jpeg
381255B1-C439-4ECB-A367-63ED7D479806.jpeg [ 21.69 KiB | Viewed 258 times ]


Last edited by deckard on 30 Apr 2021, 01:27, edited 1 time in total.
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 Post subject: Re: Stripped Label killed my player
PostPosted: 30 Apr 2021, 01:27 
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I've used regular glue, would use something like spray 77 but spray the backside of the label and then reattach.

I think I used the blue painter tape and taped the label down on cardboard, sprayed etc.

Hear that skidding sound, its slipping, the rubber mat needs to be cleaned and or replaced.
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 Post subject: Re: Stripped Label killed my player
PostPosted: 30 Apr 2021, 01:34 
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> Hear that skidding sound, its slipping, the rubber mat needs to be cleaned and or replaced.

Strange - I replaced the rubber mat just a few weeks ago. Also, the disc doesn't have any trouble stopping (before I changed the mat it used to spin for ages when stopping the video essentials LD).

I just cleaned the mat again with Isopropyl Alcohol (99%), sadly didn't make a difference :(
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 Post subject: Re: Stripped Label killed my player
PostPosted: 30 Apr 2021, 01:45 
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Here’s another video. This time attempting to play the LD in test mode.

The disc is wobbling quite badly, and the motor sounds like it’s struggling.

It certainly sounds like it’s slipping. Could the problem be with the upper clamp?

https://youtu.be/LvFUk97blwI
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 Post subject: Re: Stripped Label killed my player
PostPosted: 30 Apr 2021, 03:00 
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Sounds like the spindle is not fully pressed up against the clamp to me. Maybe check the loading assembly to see if it’s having an issue fully engaging?
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 Post subject: Re: Stripped Label killed my player
PostPosted: 30 Apr 2021, 03:31 
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deckard wrote:
Does this look wrong?

Yes.

It should look like this: https://www.repairfaq.org/sam/cdeye.gif (https://www.repairfaq.org/sam/cdfaq.htm is informative in general.)
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 Post subject: Re: Stripped Label killed my player
PostPosted: 30 Apr 2021, 05:17 
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cplusplus wrote:
deckard wrote:
Does this look wrong?

Yes.

It should look like this: https://www.repairfaq.org/sam/cdeye.gif (https://www.repairfaq.org/sam/cdfaq.htm is informative in general.)


OK, that's what I thought it should look like. So it's not getting a good RF signal. Interesting. Here's what I know so far:

1. The problem started when a label got ripped off and stuck in the machine.
2. The player won't play CD's or LD's.
3. LD's seem to slip a little bit, but CD's seem fine.
4. In Test mode, with an LD inserted the motor repeatedly speeds up and slows down. The LD wobbles a lot.
5. The RF pattern of a CD playing is totally messed up.
6. When loading a LD in normal (not test) mode, the disc rises, spins momentarily, then either stops - or spins backwards at full speed.
7. When spinning backwards - there is no wobble. Same is true on side B. In other words, when the motor is running fast, there's no wobble in either direction.
8. When loading a CD in normal mode, The CD attempts to access data twice (about a second each time). When it fails it just stops.
9. I can't see any damage in the player - no scuff marks, scratches or broken plastic.

I think that the wobble in 4 is related to the motor spinning up and down, since no wobble is visible when the motor is running full speed.

My current guess is that the lost label may have struck the optical assembly, perhaps enough to mess up the focus or alignment. Has anyone had to realign a laser mechanism because of a physical disturbance? Is this likely?

Thanks for everyone's suggestions!
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 Post subject: Re: Stripped Label killed my player
PostPosted: 30 Apr 2021, 08:23 
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ldfan wrote:
Sounds like the spindle is not fully pressed up against the clamp to me. Maybe check the loading assembly to see if it’s having an issue fully engaging?


I double checked this, and it is fully engaged.

This is driving me mad now! Could I have fried the spindle motor somehow? Is it possible that it was damaged in a way that causes it to have problems at slower speeds?
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 Post subject: Re: Stripped Label killed my player
PostPosted: 30 Apr 2021, 14:53 
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I don't see how a stripped label like that could cause any of this, unless it was some freak accident. I've had to pull them from gears before, but that is the worst I've seen.

Tracking servo on/off doesn't make any difference in test mode for CD or LD?
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 Post subject: Re: Stripped Label killed my player
PostPosted: 30 Apr 2021, 18:08 
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cplusplus wrote:
I don't see how a stripped label like that could cause any of this, unless it was some freak accident. I've had to pull them from gears before, but that is the worst I've seen.


Yeah, it does seem really strange. I wish I knew more - I'm new to Laserdisc players, I've had this player for a month or so, and this is the first problem I've had. I have a fair bit of experience repairing old Jamma arcade boards, but I'm new to analog and mechanical devices. It's a learning experience!

After looking at the pictures of the label, I noticed that the stripped label was actually from side two of the first disc, and it must have been in the player for the entirety of the second disc - but at that time it didn't cause a problem. The problem only occurred when I inserted a subsequent disc, which refused to play.

It is possible, of course that the stripped label was coincidental, and perhaps the problem was a component that happened to fail at the same time?

cplusplus wrote:
Tracking servo on/off doesn't make any difference in test mode for CD or LD?


What kind of difference would you expect? In both cases I see a bad RF signal from the CD. I have a feeling the disc sounds different with tracking turned off. I'll look in more depth this evening.

I'm looking at the Pioneer Tuning Fork videos (https://youtu.be/zj8RE1EV_Q4) on youtube for some clues. I'm hoping that if I can figure out the exact stage of failure, I might have a better chance of figuring out exactly what's wrong.

Attachment:
SpindleControl.jpg
SpindleControl.jpg [ 146.41 KiB | Viewed 205 times ]


Either the disc speed is messing up is failing in the first stage (initial spin-up), or second (once timebase error correction comes into play). In the former case, the problem would be confined to the Motor Drive Circuit or the FG Mechanism Control. In the latter case I guess the problem would be with the laser pickup, since I'm getting a bad RF signal.

Thanks again for your help.
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 Post subject: Re: Stripped Label killed my player
PostPosted: 30 Apr 2021, 21:53 
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deckard wrote:
What kind of difference would you expect?

I was meaning turn tracking off, move to middle part of CD and turn on. But I'm not really sure how much looking at waveform will help either way.

Look at PU and make sure coils didn't get damaged or the lens obstructed. In regards to FG assy, these did have to be replaced when faulty and when bad they do cause spindle runaway. Try to make sure it looks ok. Could check two transistors that drive it, but I just find that highly unlikely to fail the exact moment the label got stuck. Just throwing out ideas, as this one is baffling to me.
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 Post subject: Re: Stripped Label killed my player
PostPosted: 30 Apr 2021, 22:08 
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cplusplus wrote:
I was meaning turn tracking off, move to middle part of CD and turn on. But I'm not really sure how much looking at waveform will help either way.

I'll try it tonight. Nothing I did seemed to affect the RF waveform. I tried adjusting VR606, and it made no visible change to the signal, which I thought was strange. Perhaps any change was hidden in the noise?

cplusplus wrote:
Look at PU and make sure coils didn't get damaged or the lens obstructed. In regards to FG assy, these did have to be replaced when faulty and when bad they do cause spindle runaway. Try to make sure it looks ok. Could check two transistors that drive it, but I just find that highly unlikely to fail the exact moment the label got stuck. Just throwing out ideas, as this one is baffling to me.


I don't see any damage to the PU. Lens and coils all look fine to my (inexperienced) eye. Perhaps there is something I've missed.

The FG assy seems fine, it's the first thing I suspected (what with it being so close to the spindle, and so fragile looking). I tested the signal with the scope, and it looks sensible. I'm planning to run some more tests with it tonight, correlating it with the ACCEL/BRAKE signals, SPDLRTN+/- and the XPLAY output mode (servo/other).

Baffling to me too! Your suggestions are greatly appreciated. I usually quite enjoy debugging these kinds of problem when I'm working on video game boards, but in those cases the parts are usually generic, readily available and cheap! The prospect of a part being expensive, or worse unavailable is quite alarming!
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