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  #1  
12-11-2020, 09:08 PM
keaton keaton is offline
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I struggled a bit with whether to post this in the Capture or Hardware Repair section. My main question is whether this hardware has a glitch, and not if I have some capture setup issue. Feel free to move this to Hardware Repair section if that's a better place.

My primary reason for posting is to tap the brain power of this great community to see if others have witnessed something like this. Those who have worked on these machines or just seen a lot of them in action could be especially helpful. I hope I can get a better sense of whether this is just the nature of these machines even when properly serviced, or if I just got really unlucky despite doing everything right.

There is a color issue I've seen many times now with playback on my Panasonic AG-1980, which I've had for a couple of years now. It is specific to some EP speed recordings. I have yet to see this issue with any SP or LP recordings. For a given EP recording, it either does this 100% or 0% of the time. It can even occur on one EP recording, but not another EP recording, that are both on the same tape. It also seems independent of whether the tape has been heavily played, poorly recorded, or well preserved/recorded. It is a mystery to me as to which recordings will cause it. Switching TBC on/off or adjusting tracking has no effect. It happens with direct connection from output to TV or capture card. At first I thought it was a fluke. But with the hindsight of time, I now see the issue has been there since I got it and happens with perhaps 1/3 to 1/2 of the EP recordings I've played. These recordings have come from a lot of different machines. I have a number of "lesser" VCRs that play the same recordings without this issue. But, of course, they don't have the TBC and DNR that the 1980 has. I have tried JVC. But for EP, I really prefer Panasonic.

I have read a lot of forum posts about potential issues with this model. However, I don't think I've ever seen the specific issue I'm going to show here mentioned in any of those discussions. Or if I have heard of something like it, it was on a unit that had not been properly refurbished/recapped or had a bad Y/C board, etc. Mine was completely refurbished mechanically and electronically (yes, including the Y-C board) and came from a very reputable/experienced seller that is recommended by this forum. I've had it serviced by the same place I bought it from for an unrelated issue. So it's gone through a rigorous inspection twice now.

Despite my big disappointment with this flaw in my 1980, I've come to the conclusion thus far that I have a solid machine that happens to have a very nasty quirk on a decent % of EP recordings and that may not have any way of being resolved due to the indeterminate nature of the issue. Perhaps it's rooted in it's very complex design, combined with the fragile nature of EP recordings. Although, it is hard to accept this issue happens as often as it does on a machine so often dubbed as "the best" when it's been properly serviced. I have a few VCRs that are nowhere near "the best", and none of them have done anything like this.

I'm conflicted, and want to hold out some hope that I can find another 1980 that won't behave in this way. So, I'm considering buying another one, which would also have to come from a very reputable source. However, what I wish I could know before risking a lot of money is if this issue is rare for a refurbished unit or if this is a more common phenomenon for an otherwise healthy deck and I should not expect a high chance of this issue going away entirely by buying another one.

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The Issue:
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I've attached 4 Lagarith encoded avi files. yuvhist-1980.avi is a clip with an Avisynth YUV histogram on the right. vectorscope-1980.avi is the output from the Virtualdub ColorTools Filter in Vectorscope mode for the same clip (with the Avisynth histogram removed). Similarly, the yuvhist-4561.avi and vectorscope-4561.avi files are the same thing, but from a Panasonic PV-4561 (a standard mid 90s run of the mill VCR, but a good one for it's class).

This clip has a lot of neutral areas, namely the greyish background and the black outfit. In the 1980 clip, you see these neutral areas drifting through various color casts. Red is one example seen here, but there are other color shifts as well. You can see the V channel shifts more to magenta side for a moment and then back. When this happens, the image has a noticeable shift to a reddish cast. Similar things happen in the U channel to either the blue or yellow side.

Focusing on the center of the 1980 vectorscope clip, notice how the color data drifts together in various directions with respect to the center of the graph. It seems like a circuit cannot keep a lock on the chroma signal.

When you observe the 4561 versions of these videos, you see the U and V channels are very stable and do not drift as you see with the 1980. I also don't notice any color shifting in the video as I do in the 1980 clip. The 4561 vectorscope is notably different from the 1980 and does fluctuate a bit in magnitude. However, I don't see it "drifting" or "shifting" with respect to the center of the graph as the 1980 is doing.


I really hope to get some responses that may help me make a more informed decision with whether to seriously consider trying my luck again on another 1980. I want to believe I just had really bad luck even though I bought from an excellent source, and this wouldn't happen to me again if I got another properly serviced machine. I feel like I've done all I can with the one I have, and I shouldn't sink more money into it. However, I know it would be maddening to get another only to find this issue is more common than I would have hoped.


Attached Files
File Type: avi yuvhist-1980.avi (82.51 MB, 15 downloads)
File Type: avi vectorscope-1980.avi (3.99 MB, 11 downloads)
File Type: avi yuvhist-4561.avi (83.04 MB, 13 downloads)
File Type: avi vectorscope-4561.avi (5.08 MB, 5 downloads)
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  #2  
12-29-2020, 11:24 AM
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lordsmurf lordsmurf is offline
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I can't open video clips on my tablet, but wanted to reply for now. One of one decks came back from TGrant with excess chroma noise, some years ago, and had to be sent back. He did fix it on the 2nd pass. It was very obvious red/blue noise to the naked eye, and I have sample clips on my main system.

BTW, that deck has again failed, the refurb didn't take. I'm starting to think TGrant doesn't replace all caps, just bad caps -- and that's not good. A $400 refurb should last more than 2-3 years. Stuff like this is causing me to really hate AG-1980 decks, money pits. But a necessary evil to do what I do. Aggravating.

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  #3  
12-29-2020, 12:46 PM
hodgey hodgey is offline
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I'm spotting a luma noise pattern as well, it's pretty faint but you can see these "stripes" slowly making their way upwards. It's a bit like a type of noise I've seen be caused by bad power supplies in other devices (I think it's like 60Hz ripple that isn't completely filtered since it's nearly in line with the frame rate), so maybe the PS in the unit have one or more bad caps. If there is 60Hz ripple coming from somewhere, that could mess with the color decoding cirtuits in the VCR in addition to causing noise, especially in a unit like the 1980 with it's digital video decoder.

EDIT: Okay, maybe I'm wrong, it's there on the clip from the other VCR as well, maybe it's actually something that happened when the tape was recorded.
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  #4  
01-03-2021, 04:38 PM
keaton keaton is offline
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Thanks for the replies. I have since contacted the dealer I bought the unit from, and was able to describe what I was seeing in the histogram and vectorscope over the phone. The dealer seemed rather familiar with the symptoms I described, especially the color fluctuations in flesh tones, so I suspect this is not a rare occurrence with this model. The initial diagnosis was likely that the Y-C board has a bad crystal (oscillator), which is causing the loss of lock on the color signal. A bad capacitor could also be a possibility. The dealer was fairly confident that it is better to repair this unit than to put that money towards another unit. It will be a while before I get the unit back. This is due to lots of units already in the queue ahead of mine. Hard to know if the high volume is due to a business sending in several units at once or if there's lots of individuals like me that are continuing to have something else go south. Also impossible to know if the failures are due to heavy use or some other inherent instability with these machines.

This is the only 1980 I have owned, and has otherwise been a rather stable unit for a light user such as myself. I am experiencing the same frustrations as so many others have expressed about these machines. Even though we all know that there is little to no warranty on the units after being serviced, we still pay significant costs to have them fixed because we know just how good they are when they are working correctly and really want to hold out hope that it will be a long time before the next failure. These really are only for those with significant discretionary funds who can take the risk.

It is a curiosity of mine whether the continued issues people experience after having them refurbished is due to only fixing what is wrong with them at the time (i.e. not doing a replacement of all parts likely to fail in the near future) or if there is something inherently unstable about their design that causes even a fully electrically restored machine to have a shorter life than you would expect. I suppose the complexity of the design must be a contributing factor when considering why so many of these experience faulty behavior.

The initial diagnosis of a bad oscillator leads me to believe that a refurbished unit does not imply that all parts with a decent probability of failure in the near term are replaced. That is a frustrating thought. Although, I don't know the life of an oscillator. I suppose anything over 20 years old cannot be expected to live longer. If it turns out to be that only an old oscillator needed replacement, it would be somewhat reassuring. Going back to the understanding that even refurbished units have risk, then I could conclude that it was just bad luck that despite all the caps still being good, another electrical part has failed after 20+ years. If that is the case, it allows me to have hope that these units can still live a significantly long life once all the aged parts have been replaced, assuming the heads and mechanical parts haven't been worn out.
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  #5  
01-03-2021, 07:19 PM
dpalomaki dpalomaki is offline
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The drift, mainly along the x-axis, implies a slight drifting of the frequency resulting on a phase shifts that in turn cause the tint to drift. That it is slow drift is interesting.

The typical 1980 rehab addresses electrolytics because that is the chronic issue, but other parts could well become less stable over time as well. It could be purely electrical in nature, or possible a combination of electrical and mechanical; e.g., certain tapes cause some form of microphonic vibration that impacts the oscillator stability. That the drift is slow could map to something like the rotation speed of a supply or take-up reel or idler that interacts with your specific VCR. The magic and mystery of electro-mechanical analog systems.

Lets hope the repair works OK.
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