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staffanu
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Post subject: [LD-V8000] Sudden tracking problem Posted: 09 Feb 2021, 10:45 |
Genuinely interested |
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Joined: 24 Sep 2020, 02:47 Posts: 35 Location: Sweden Has thanked: 1 time Been thanked: 21 times
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I have an LD-V8000 that has worked flawlessly for a few months (got it it cheap and had to re-grease the rails for the pickup assembly to get it to work). Anyway, as of yesterday it suddenly won't play discs anymore.
I guess it is not related, but I've had the same disc in the player for along time, and swapped it for the 8" GGV-1069 yesterday to get a test signal for my tv (how nice it would be to only have to fix one thing at once for a change:) ). This player normally takes a while before starting to play a disc, but I thought I heard some unusual ticking noises and it took a while (longer than normal), but the disc played after a while. Swapping back to a standard movie and it didn't ever start playing -- seeking around at the end of the disc forever (reading all over the disc is normal for this player).
Now, if I enter test mode and start playing a disc, everything is as usual, until I turn on the tracking servo. When I do this, the player skips forwards really fast -- not just "fast forward" but forwarding an entire side in 5 seconds or less.
I had a quick look at the tracking error signal (as per the temporary grating adjustment) and it looks fine -- as does the tracking balance adjustment. (Of course I don't know if it is really at a maximum, but p-p it is about 800 mV, which, from memory, is about the maximum I could get.)
Any ideas what could cause this? (I'm of course afraid there's something wrong with the tracking mirror, but hoping for an electrical problem.)
Staffan
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staffanu
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Post subject: Re: V8000 sudden tracking problem Posted: 06 Jun 2021, 18:42 |
Genuinely interested |
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Joined: 24 Sep 2020, 02:47 Posts: 35 Location: Sweden Has thanked: 1 time Been thanked: 21 times
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Long time but I'm finally back at this again. I've done some adjustments (1-7) and the player plays both CAV and CLV disks again, with acceptable picture quality.
Everything's not good, however:
- First, it is difficult to get the player to start playing discs. In service mode, after pressing Play twice to switch on focus (first press is laser on, second focus on), the lens mostly just sits there moving up and down looking for focus. It sometimes locks focus after some time, but what I found is that if I move the pickup to the start of the disc, the chances are higher. Also, by bending the disc up/down by touching the edge and lifting/pressing down lightly (not much -- maybe 1/2 mm) the player always locks focus. After this, it will play the entire disc just fine.
This doesn't make any sense to me since observing the focus return waveform it is clear that the moving up/down of the pickup crosses zero clearly, without me touching anything. So I fail to see what difference it can make. Anyway, maybe this is a clue?
In normal play mode the player mostly doesn't even attempt to focus. I wonder what makes it give up? I can sometimes get it to play a disc if the pickup is at the very start of the disc when it is turned on. I wonder what the logic is that moves the pickup around a bit after powering on -- I fail to see a pattern.
- I also went through doing adjustment #8. When I reconnect CN28, the player indeed runs the tilt servo. It just doesn't seem to work very well. Mechanically it does -- no strange noises and the back of the pickup rail moved up and down, but the movements are rather large and I can rarely get the player to play anything without disconnecting CN28 and manually re-doing adjustment #3.
When thinking about the whole thing, I fail to see how the player is supposed to differentiate between tilt error and focus balance. Obviously the tilt servo affects both, since it adjusts the shaft levelness and also the distance from the pickup to the disc. Maybe it doesn't have to, and the way it works is that it tried to keep the tilt error close to zero (using a low pass filter to read the error signal), while keeping the lens focused (which it has to do much quicker).
So again, if any of this makes anyone think of anything I should check please let me know!
Thanks!
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staffanu
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Post subject: Re: V8000 sudden tracking problem Posted: 11 Jun 2021, 21:52 |
Genuinely interested |
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Joined: 24 Sep 2020, 02:47 Posts: 35 Location: Sweden Has thanked: 1 time Been thanked: 21 times
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One new observation, or rather a correction, of what I said before:
Focus is obtained when the laser sits just before the lead-in -- that is, the blank area in the middle of disc. I've tried to perturb the process when it is looking for focus and thought that wobbling the disc manually sometimes helps. After a long time of repeatedly staring and stopping the player today, what helps is bringing the pickup just a tiny bit too far to the inside of the disc. After that, it often starts playing the lead-in by itself, and when it doesn't, it does if a touch the slide drive a minimal amount to the outside.
So, I assume focusing on the plank part of the disc is different from focusing on a recorded area. cplusplus suggested checking the laser power but I don't understand how to do that. Maybe it is too weak?
Staffan
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staffanu
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Post subject: Re: V8000 sudden tracking problem Posted: 13 Jun 2021, 00:12 |
Genuinely interested |
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Joined: 24 Sep 2020, 02:47 Posts: 35 Location: Sweden Has thanked: 1 time Been thanked: 21 times
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I realized I had to check this too: bringing the pickup to the outer edge of the disc -- the mirror looking non recorded part -- also successfully locks focus. So it seems that for some reason the player's ability to focus limited, and for some reason it seems to work when there are no tracks under the pickup. Once focus is obtained, however, things seem fine. I've not yet seen it lose focus once obtained. The second part of the service manual (Service Guide, ARP 1759), page 16, has some information about the focus servo (section 4.2). I notice that the TRKG A+B signals are used for something but I just don't understand how. I'm thinking that at the blank parts of the disc the tracking signals are probably quite different than when at a recorded part, some maybe that is a clue? I'll think about this more after some rest! Staffan
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cplusplus
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Post subject: Re: V8000 sudden tracking problem Posted: 16 Jun 2021, 19:38 |
Hardcore fan |
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Joined: 13 Aug 2018, 03:18 Posts: 1529 Has thanked: 454 times Been thanked: 592 times
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Did you adjust grating? Either way, I'd revisit #3 and #5. Can you send service guide to manual@lddb.com?
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staffanu
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Post subject: Re: V8000 sudden tracking problem Posted: 20 Jun 2021, 13:11 |
Genuinely interested |
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Joined: 24 Sep 2020, 02:47 Posts: 35 Location: Sweden Has thanked: 1 time Been thanked: 21 times
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Hi, Yes, I did adjust grating, and I'm starting to suspect that I might have used a "false" on track position. I tried doing this again and have re-done #3 and #5. Still not working, however. I did find this note on the domesday86 website, the the obsolete instructions for adjusting the ld-v4300d, on #4 (Pick-up tracking and tangential direction inclination adjustment): Quote: Note: If alignment is out the player may refuse to spin up the disc. In cases where the alignment isn’t too far out, pressing lightly on the disc-edge over the centre line of the pick-up can be enough to cause the player to start spinning.
The thing is I do not have much crosstalk, and I did make same small adjustments to the inclination and now I think it is totally gone. The service guide I'm talking about is part of the pdf already available at lddb: https://manuals.lddb.com/LD_Players/Pioneer/LD/LD-V8000/LD-V8000-EN_Service_Manual_Scan.pdfIt starts after page 128 of the first document in that pdf. Staffan
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staffanu
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Post subject: Re: V8000 sudden tracking problem Posted: 21 Nov 2023, 01:37 |
Genuinely interested |
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Joined: 24 Sep 2020, 02:47 Posts: 35 Location: Sweden Has thanked: 1 time Been thanked: 21 times
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A late follow-up in case it helps someone! The player has been standing awaiting further attention for quite some time, but yesterday I had a go at it again. The state was the same as where I left it: difficulty getting focus at all (which is a bootstrap problem in that the adjustments require the ability to play a disc). After cleaning the lens (the player had been standing opened up on the floor for a few years -- don't do that! ), as before, focus could be locked by manually moving the pickup to the clear area of the disc inside or outside the recorded section. (I just moved the assembly gently using my hand -- compared to many players this is very easy due to the fact that no gears are involved.) I went through all the calibration steps from the manual up to step 10 -- I was too lazy to remove the DTMC assembly required for the later steps due to all the cabling that needs to be removed in order to get to it. Everything works perfectly from what I can tell, so I'm happy at this point. I'm not sure, but I believe that I might have used a "false" on-track position before. To be honest I think it is really hard to tell two or three of the "almost on-track" positions next to each other apart: they all have similar looking "smooth" tracking error signals. So I started on one side, picking the "top" after what I thought could be the correct on-track position, and with the screwdriver still in the adjustment hole, closed the tracking servo. First time tracking wasn't great, so I opened the tracking servo and adjusted to the next top. This seemed fine, but I actually adjusted to the next also just to be sure. But it was bad again, so moved back. The reason to keep the screwdriver in the adjustment hole between trials is that I think it's quite tricky to get it into position. Anyway, being certain that I had the correct coarse tracking adjustment, the player worked fine up to about frame #20000 albeit with some unusual noise. After frame #20000, it still did some skipping, and the initial focus problem was still there. It turned out that the pickup centering adjustment was very bad, and that was the adjustment that made a big difference. I still went through all the steps, but frankly didn't notice any difference fine tuning everything else. I still don't quite understand why centering is important for initial focus -- anyone that knows that can explain? Actually, it seems to me that any difference it could make should we worse close to the center of the disc (where the radius of the tracks is smaller), i.e., any angular error due to centering offset should be worse. That is apparently not the case, however. The tilt stay inclination was also off by quite a bit, but I saw no visible or behavioral difference adjusting it. Staffan
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