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 Post subject: V8000 sudden tracking problem
PostPosted: 09 Feb 2021, 10:45 
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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.)

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 Post subject: Re: V8000 sudden tracking problem
PostPosted: 09 Feb 2021, 20:20 
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Was the disc sitting clamped for a long time? If so, I'm not sure if this could be some sort of loading related issue. I am not familiar with the LD-V8000.

Does closing tracking servo on the inner part of the disc result in the same behavior if you close the tracking servo on the outer part of the disc?
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 Post subject: Re: V8000 sudden tracking problem
PostPosted: 09 Feb 2021, 21:37 
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Not a very long time -- it could have been clamped for a week at some point but I've been using the player more or less daily the last month and have switched sides sometimes. Apart from that I'm clumsy enough to sometimes accidentally eject the disc when just stopping it.

And yes, closing the tracking servo has the same effect all over the disc.

The turntable spinning sound has not increased in a way that I can detect, so I assume the disc is more or less centered.
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 Post subject: Re: V8000 sudden tracking problem
PostPosted: 09 Feb 2021, 22:57 
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I now had a look at the Lissajous waveform measured when doing pick-up assembly centering adjustment and it looks fine.
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 Post subject: Re: V8000 sudden tracking problem
PostPosted: 10 Feb 2021, 02:04 
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Given that this unit has been stationary and the issue was sudden, I'm thinking something has failed in the electronics.

An old service advisory I see says to make sure the lens is getting .2mw

Since you have a scope, I would just go through checking the rest of adjustments (particularly #5 if you have not yet). Also maybe make sure the pinion gear mentioned in Adjustment #3 has not become damaged somehow.

Just throwing ideas out there.
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 Post subject: Re: V8000 sudden tracking problem
PostPosted: 11 Feb 2021, 14:47 
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Thanks for the suggestions! I didn't have the time to work on this yesterday but plan to later tonight. Is the service advisory available online somewhere?

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 Post subject: Re: V8000 sudden tracking problem
PostPosted: 12 Feb 2021, 00:08 
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I started by checking Adjustment #3 -- the pinion gear is fine, and at the moment it is disconnected since most of the adjustment requires it to be. The focus return voltage is very close to 0 (between -5 and +5 mV over the entire disc).

For #5 I cannot really perform the adjustment since I have no way of playing a disc in normal mode.

BTW, does anyone know what amplitude the tracking signal is supposed to be (when tracking is open)? I have 0.8 V p-p. Looking at Photo 10, p 103, in the service manual it looks as if 300 mV is normal, but looking at wave form 1, p25, it looks more like 1.2 V or so.

A completely different thing: is it normal for the power supply to run quite hot? I've noticed this also when the player was working: the larger caps and the cooling plates at the back of the psu is around 60 C (140 F).

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 Post subject: Re: V8000 sudden tracking problem
PostPosted: 12 Feb 2021, 01:34 
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Advisory is from an old Pioneer DB and that is all that it says. No service bulletin associated with it. I will be posting all of that once I get it organized.

Just checked tracking error with a player I just put on the bench and it shows a little above 250mv with tracking open. Waveform should look like the one in Photo 10.

Not sure about the power supply heat.
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 Post subject: Re: V8000 sudden tracking problem
PostPosted: 22 Mar 2021, 12:35 
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Well, I couldn't figure out what was wrong so I tried replacing the optical assembly with one from an otherwise completely broken V8000. It would seem there is some problem with the original pickup as the player now plays discs again.

Very strangely, CLV discs play (not perfectly but no skipping), but CAV discs do not play at all. I tried maybe 3 discs of each kind, including the GGV1069 (CAV).

When playing CLV discs there is some noise in the picture indicating that something isn't perfect. I don't know if this is due to the optical assembly is in as bad shape as the rest of the donor player or if it just needs adjustment -- I'll try making some adjustments later.

I can play CAV discs in test mode (in normal mode the player gives up during the initial scan/indexing of the disc), and it does play them but with poor quality. The biggest problem is that the picture is not stable horizontally.

Any ideas what could cause this? I assumed that CAV would always play better than CLV...

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 Post subject: Re: V8000 sudden tracking problem
PostPosted: 22 Mar 2021, 15:17 
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You will need to run through the adjustments after exchanging pickups.
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 Post subject: Re: V8000 sudden tracking problem
PostPosted: 22 Mar 2021, 15:41 
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Yes, I assumed I would but was mostly interested if the symptoms are consistent with a non-adjusted player. The CAV/CLV situation still surprises me, adjusted or not. I'll post an update when I've had a go at the adjustments.

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 Post subject: Re: V8000 sudden tracking problem
PostPosted: 06 Jun 2021, 18:42 
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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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 Post subject: Re: V8000 sudden tracking problem
PostPosted: 08 Jun 2021, 22:08 
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Can you check to see if the white attached to #26 DXB1118 Tilt Shaft Assembly is cracked?


Attachments:
LD-V8000_Tilt.jpg
LD-V8000_Tilt.jpg [ 44.52 KiB | Viewed 305 times ]
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 Post subject: Re: V8000 sudden tracking problem
PostPosted: 09 Jun 2021, 17:04 
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No, it seems good.

The only thing that's weird to me is that the spring (#27) seems too short -- it is gives no pressure whatsoever about half the travel way of the servo. But this is consistent with my other 100% working LD-V8000 so doesn't seem to be a problem. Still curious if it is a design flaw or a clever mechanism I don't understand:)

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 Post subject: Re: V8000 sudden tracking problem
PostPosted: 11 Jun 2021, 21:52 
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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?

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 Post subject: Re: V8000 sudden tracking problem
PostPosted: 13 Jun 2021, 00:12 
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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! :)

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 Post subject: Re: V8000 sudden tracking problem
PostPosted: 16 Jun 2021, 19:38 
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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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 Post subject: Re: V8000 sudden tracking problem
PostPosted: 20 Jun 2021, 13:11 
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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.pdf

It starts after page 128 of the first document in that pdf.

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