Quantcast Samsung SV-7000w (aka Panasonic AG-W3) losing and reappearing image? - digitalFAQ Forum
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  #1  
04-18-2018, 06:51 AM
hodgey hodgey is online now
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When playing a tape on this machine, the image keeps going from fine, to nothing to fine and so on. It looks a bit like tracking thing or goes out and in of alignment. See the attached video for a better illustration. Any thoughts on what could cause this? The issue just randomly started one day after working fine in the past.


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File Type: mp4 samsung_prob.mp4 (17.90 MB, 9 downloads)
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  #2  
07-15-2018, 09:42 AM
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Still having this issue.

Came across https://www.youtube.com/watch?v=R9S2M0UQ-nw where a machine with a similar issue was fixed by cleaning the contacts on the ribbon cable going to the control heads. That doesn't seem to be the issue I have though, the ribbon cable connections seem fine when measuring with a multimeter, and the linear audio signal is output fine. Based on the video and the VCR faq I do suspect it's something with the tracking signal not being used properly though (granted my knowledge of VCR internals are limited.) Adjusting tracking on the vcr has no effect whatsoever on the image besides showing the tracking OSD, which I presume is related? Would the servo lock flowchart in the service manual be the right thing to look at?

I also found a yt video of someone with the exact same issue on a SV-5000w (which is mostly the same internally).
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  #3  
07-19-2018, 06:36 PM
NJRoadfan NJRoadfan is offline
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Check the capstan speed. If the circuit controlling it is going on the fritz, it'll do weird things like that. Sony Betamax decks had that problem due to bad caps on the capstan motor control board.
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  #4  
01-14-2019, 05:28 PM
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A little update on this.

I may have solved it, I don't know for sure but I think the issue may have been with one of the two connectors that connect the drum and the other motor to the board. I'll take a picture of them tomorrow. At least it worked after taking the mechanism out and putting some electronic cleaner on the concatcs and putting the mechanism back in the tracking worked normally again. (Also don't put the big slider on SQPB only )
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  #5  
01-24-2019, 01:06 PM
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Update2

That didn't seem to solve the issue apparently, servo lock/tracking still only works occasionally. It seems like there is bad contact someehere but I haven't found out where.
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  #6  
08-14-2019, 06:41 PM
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So a while back I randomly came across a Samsung SV-6213X deck, which it turns out has a pretty much the same mechanism other than the drum some of the plastic bits on the loading tray. While the exact model is not in it, this list has a bunch of decks using this mechanism as well. (though I saw another one that had the one shared with some models in this one).

SV-7000W on the right:
IMG_20190814_185406.jpg

And sure enough, putting the mech from the SV-6213X into the SV-7000W worked, but produced the same issue. The reverse, putting the mech from the 7000W also worked in the older one, and sure enough in this case the servo locks fine and plays back as expected other than the head switching point being a bit too high. (Something that's super easy to adjust on these VCRs).

Of course the interesting bits of the 7000W is the electronics rather than the (rather shoddy) Samsung mechanism, but at least I know the mech itself is fine, so onto hunting for problems on the PCB I guess, maybe I'll try to reflow the capstan connector next.

Anyhow, what's interesting for others here is that if you have one of these Samsung multisystem SV-5000W, SV-7000W and presumably the panasonic analogue/rebadge, you can find parts for the mechanism in cheaper Samsung decks if they break. Not sure if the other models (4000W, 3000W, 300W etc) use the same mech but they likely share it with some non-multisystem decks as well.

Another interesting bit, the deck seems to act a bit as a stabilizer/frame sync of sorts when in conversion mode (or with art mode turned on when playing video). Not sure if there's a way to force it to pass through the A/D chain without converting otherwise, and composite only of course, but cool neverthless.

See the difference captured with a Diamond VC500 when ffwding on another deck here between PAL (passed straight through) and PAL-N(conversion on, as it's read as PAL-N colours are whack obviously):
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The VCR has a Philips SAA7113H A/D chip, the capture dongle I have with the same chip will balk at this so whatever is connected to it has some impact.


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  #7  
08-14-2020, 08:38 AM
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In case anyone comes across this. I found the problem, there was a little crack in the main PCB that broke the connection between the control head and system IC. Bridging the crack with some wires fixed it.
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  #8  
08-14-2020, 09:43 AM
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What do you suppose caused that crack?
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  #9  
08-14-2020, 09:48 AM
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I have no idea, the VCR just started acting up one day, maybe the previous owner dropped it or the board got stressed in shipping, or maybe something caused a weak point there during manufacturing. It's a very small crack that's only on one side of the board from one of the holes the plastic mounting protrusions in the outer chassis go through.
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  #10  
08-14-2020, 09:50 AM
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Did you find it by electrical testing or through visual inspoection?
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  #11  
08-14-2020, 09:58 AM
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After seeing that there was no control signal coming out of the CTL test point (and comparing to the Samsung VCR mentioned earlier in this thread which is not multi-system but otherwise very similar), I started checking for continuity between the CTL+ and CTL- lines between the connector for the audio/control head and the system IC. That led me to a spot on the board where there was no continuity and a visible line on the board going through the traces. I think I ended up tracing the wrong line last time I looked at it.

The crack/split/whatever seemed to end up also breaking contact at one point with the 5v power to part of the video IC after I bridged the control signal, so had to fix that as well. I put some epoxy on it in the hope it would prevent it from tearing further, but i don't know if it will make any difference.
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  #12  
08-14-2020, 10:01 AM
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Thanks for the insight!
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  #13  
08-14-2020, 10:04 AM
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These particular VCRs go for as much or more than high-end SVHS VCRs so I'm glad I managed to fix it.
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  #14  
08-14-2020, 10:05 AM
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Also, the satisfaction of doing it yourself adds to the sense of achievement.
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