digitalFAQ.com Forum

digitalFAQ.com Forum (http://www.digitalfaq.com/forum/)
-   Video Hardware Repair (http://www.digitalfaq.com/forum/vcr-repair/)
-   -   Panasonic NV-HS1000 noisy image, random spots? (http://www.digitalfaq.com/forum/vcr-repair/8525-panasonic-nv-hs1000.html)

hodgey 02-28-2018 09:03 PM

Panasonic NV-HS1000 noisy image, random spots?
 
1 Attachment(s)
So we got a Panasonic NV-HS1000 a few months ago. Originally it seemed to work fine, but lately it seems to have developed some significant playback issues. It's seems to be most pronounced at the start of tapes, often there is barely any visible image (as if the tracking was way off), but it gradually clears itself after a while. Additionally, the same seems to happen at random spots during playback. My description is may not be the best, so I've attached a video sample of the start of a commercial tape, which works well in the 3 other VCRs I've tested. The problem seems to be generally worse on home tapes (the issue doesn't happen on any other VCRs so I don't think the tapes are the issue). I also noticed when looking through the video before uploading that there is some audio interference at various places, this tape has linear audio. (The picture rolling with he green line is the TVOne TBC freaking out from the bad signal, sorry about that, I can do a new capture without it if it helps.)

I've tried to clean the heads and tape paths, though it doesn't seem to help much. I did accidentally play a tape that left some white gunk in the machine, I suspect that may have caused some issue, or maybe I've misaligned something when cleaning at some point.

Quasipal 03-12-2018 09:15 AM

One time I had an HS1000 that arrived in mint condition that did what you described. The guides were out of adjustment. After adjustment the machine worked perfectly and to this day I don't know what caused this. Maybe an impact during transit?

Maybe yours is the same?

hodgey 03-12-2018 09:54 AM

Possibly. It seems to have mostly resolved itself now though after a thorough cleaning, at least for the commercial tape. It may just have been some tapes that were shedding that caused the problems, as they did cause some minor clogs on other machines too. I also found some dust stuck to one of the guides when cleaning, which may have messed with the positioning. Will have to see if it starts happening again with home tapes or not.

-- merged --

Do you have any pointers to checking whether the guides are ok (or does that require an oscilloscope?). The unit still seems to be prone to get what looks like a minor head clog on certain tape spots (much more than any other VCRs we have here) giving a very noisy image similar to the video I posted but clearing up shortly after.

Besides cleaning, I did try to clean under and on the anti-static brush, which seemed to help a bit, but I don't know if i did it correctly. Is there a way to check, like with a multimeter, if it makes good contact, or would that not work?

Quasipal 04-13-2018 11:16 AM

As long as the contact between the anti static brush and the head is cleaned with something like IPA then that is good enough. It just bleeds static to ground.

As to your problem it may a combination of factors at work. The HS1000 was designed to record and play VHS at maximum quality on new or perfect condition tapes. It is not very tolerant of worn or creased tapes which show larger than normal dropout and lines on screen. I think (only guessing here) that this was done to get the best quality possible, as they thought that most users would not be playing old tapes.

Also for some unknown reason the HS1000 hates TDK SVHS tape stock. Clogs the head repeatedly. I'm not the only one to notice this and I don't know why it happens.

Lastly if the heads are a bit worn the protrusion is less so less self cleaning goes on as well as less contact with the tape across damaged or marginal sections of tape. This manifests as worse clogging and lines on screen.

For worn or dropout infested tapes I turn to my FS200 which often is much better on such tapes (but worse on others).

Hope this helped a little.

lordsmurf 04-13-2018 08:49 PM

Quote:

Originally Posted by Quasipal (Post 53737)
Hope this helped a little.

I always enjoy reading your comments.
Even though I'm a NTSC Panasonic user, sometimes your info can be extrapolated. :wink2:

Quasipal 04-14-2018 03:43 AM

Only too happy to share what I know. I never could stand those old time technicians who lurked in their smoke filled workshops unwilling to give the smallest bit of help or info to a budding enthusiastic young lad.

hodgey 04-14-2018 08:52 AM

Okay, thanks for the help.

Another maybe silly question while I'm at it. The VCR came with one of these things) rather than the original remote. Generally it works okay, and most of the functionality is accessible on the front panel, but I've used it for manual tracking (I didn't find any way of doing it with the front panel buttons). Now to disable manual tracking and go back to auto-tracking you're supposed to press both tracking buttons on the original remote, but I'm not sure if that works properly with the replacement one. Is there some way to reset the vcr to the default settings, or does the tracking reset itself when a cassette is ejected?

Quasipal 04-14-2018 08:53 AM

Resets every time a tape is inserted.

hodgey 11-13-2018 05:19 AM

3 Attachment(s)
Another question:
Do these decks have barely any masking/compensation of dropouts, or is something not right with this particular one? Based on the earlier reply from Quasipal I wouldn't expect it to be super advanced, but even my cheap Samsung VHS deck does it much better, these black lines get very visible if the tape is not in superb condition. (And for that matter the AG7350 broadcast deck which I would not expect to be particularly tuned to bad tapes.)

NV-HS1000
Attachment 9112
Samsung SV-261x
Attachment 9113
Philips VR1100
Attachment 9114

Quasipal 11-13-2018 08:49 AM

Sorry but black or grey lines when tape is in poor condition is what these decks do. However, and I don't know if this is a one off, I have an HS1000 as a daily user and plugged in all the time and that hardly shows dropouts. All my othet 'plug in as needed' HS1000's have the lines. So maybe leave it plugged in for a full day or so. That may help.

hodgey 11-26-2018 08:39 AM

It usually is plugged in, so presumably that doesn't help. Looking at the service manual here there does seem to be and older and newer revision (EG vs EGC and B vs BYP) of the NV-HS1000 though, in addition to the differing tuner frequency variations. The newer one has some updated electronics and other components. Is the one you have that hardly shows dropouts the newer revision perhaps? The one we got here is an older (EG) one.

hodgey 02-12-2019 03:37 PM

3 Attachment(s)
After digging through the service manual it seems the YNR balance pot controls the amp that amplifies the signal coming from the delay line that is used for dropouts. It was a bit tricky to access, but after a bit of tweaking the dropouts are much less notable. I suppose it may have some impact on on the noise reduction but I didn't really notice any change there.

Attachment 9571

Left: After adjustment - Right Before
Sharpness and levels settings may be a bit different as I didn't remember what it was set to on the before shots. Also I also adjusted the PG shifter a little but this specific tape has a very low switching point already.
Attachment 9569
Attachment 9570

hodgey 05-01-2020 10:58 AM

So a little update on this after learning some more things.

I had a look at the PCBs, and did some recapping. I recapped the electrolytics in the whole power supply other than the large 400V one. Some of the 680 uF caps in the power supply had started to leak, and the 63V capacitors on the 45V line measured very high ESR. Also replaced most on the Luma/Chroma board (a few were maybe a bit borderline ESR, but none really bad), and a few other ones. There were one on the main board (16V 100uF) and one on the tuner (16V 47uF, probably not relevant if one is not using the tuner), and some 10uF ones on the in/out board (don't remember the numbers on them right now). None of this made much difference, though the leaky and bad ones were probably worth replacing anyhow. Also did all of the electrolytics in the head amp as some of them had High ESR or low capacitance when I measured. (Note that the cap values for some of the caps in the PSU are wrong in the service manual schematic for whatever reason, but correct in the parts list).

Recently someone I follow on youtube posted this video of the AG4700 (which is the pretty much identical "pro" versions of the NV-HS1000). It turned out there was a bad solder joint on the lower drum assembly connector, and sure enough, mine had the same cracked joint. Reflowing mine didn't really fix my noise streaks and signal loss issues though.

What did work was swapping out the drum assembly with the one from an Panasonic AG5700 that I had sitting around (with some other issues.) While they have different video drums they did turn out to be compatible and have the same connections. The AG5700 had the VEH467, same as the Panasonic FS200/FS8, the only service manual I have found lists another one in the parts list with the VEH467 written over it in handwriting. The NV-HS1000/AG4700 have one of two different ones depending on revision. I would have been a bit vary of it, though I assumed it would work as someone I know from working on vhs-decode had swapped drums between the FS200 and NV-HS1000 without problems.

I don't know if the heads themselves are bad, or if it's something on the drum assembly. Hi-Fi worked perfectly with the original drum so those heads are presumably fine. It's probably worth checking the solder joint if you're having issues with these though, unfortunately guy in the video I referred to didn't actually test the drum after reflowing, he only verified that the upper drum was fine, so I don't know for sure if there could be more bad joints (though I didn't spot any obvious ones at least.) or other electronics issues on the lower drum that are related to it.

pcourtney 01-20-2021 03:01 PM

ouch, I have a feeling the HS1000 I have just taken out of storage is going to need a really good service - calling Quasipal :-)

latreche34 01-21-2021 01:17 PM

The picture noise at the beginning of the sample is definitely a head clog, It is not an alignment issue since the frame is stable even with the noise at its peak, Look at the video heads with a magnifying glass make sure there is no dirt buildup around the them, If so a special cleaning is needed and should be done only by skilled individuals, I've come across VCR's like that where I had to perform this procedure of using some solvent and special wooden picks with a camera microscope and carefully removed all that buildup around the protruded heads that otherwise a paper cleaning method will not remove. The buildup makes the heads clog easily.

The best DOC algorithms are the Sony's, I believe they had a patented technology that they used in their 8mm/Hi8 format and they used it for VHS as well.

pcourtney 01-21-2021 05:26 PM

the dropout compensation control on my Sony EV-S880E Hi8 deck is pretty good, but I think JVC have pretty good DOC as well

you were the author :-)
http://www.digitalfaq.com/forum/news...pensation.html


All times are GMT -5. The time now is 06:19 AM

Site design, images and content © 2002-2022 The Digital FAQ, www.digitalFAQ.com
Forum Software by vBulletin · Copyright © 2022 Jelsoft Enterprises Ltd.