VideoHelp Forum


Try StreamFab All-in-One and rip Netflix video! Or Try DVDFab and copy Blu-rays! or rip iTunes movies!
+ Reply to Thread
Results 1 to 13 of 13
Thread
  1. Member
    Join Date
    Jun 2017
    Location
    Australia
    Search Comp PM
    I recently got my hands on an old Panasonic AG-MD835 unit and was doing some initial testing against my other Panasonic AG-5260. I was planning on doing a small write up on the unit as there is little to no information on it, but ran into an issue that is appearing in the video output. I'll provide frame output comparisons as well as the full clips for review below.

    The first test is the AG-MD835 connected through the DMR-ES10, using composite outputs for A/V from the VCR and S-Video from the DVD Recorder.

    Click image for larger version

Name:	Test 1 snap.png
Views:	157
Size:	598.4 KB
ID:	42314

    The second test is the AG-MD835 using S-Video for the output however NOT run through the DMR-ES10

    Click image for larger version

Name:	Test 2 snap.png
Views:	143
Size:	625.8 KB
ID:	42315

    The last test is the AG-5260 running through the DMR-ES10, using composite outputs for A/V from the VCR and S-Video from the DVD Recorder.

    Click image for larger version

Name:	Original snap.png
Views:	132
Size:	596.9 KB
ID:	42316

    My opinion on the few results is that the AG-5260 has a far superior output, the colours appear to be much richer as well having an overall less noisy image. The differences between the first two situations are basically none from what I can see, however I would have thought that the AG-MD835 would have at least provided a similar quality if not better image.

    My thoughts are that something is up with the unit, I haven't inspected it since I have purchased it but I do know that it was removed from a good working environment only recently and has less than 500 total hours. I'm not really well versed on VCR issues and the only things that spring to mind is either a dirty head or components otherwise, or something in the circuitry like the built in Line-TBC failing.

    I would like to get a general idea of what to start looking for, or if this is simply just a normal difference between two different VCR's.

    Note - The original test clip pertains to the last frame test and the other clip belongs to the first test (Second test clip not included).
    Image Attached Files
    Quote Quote  
  2. Member
    Join Date
    Aug 2010
    Location
    San Francisco, California
    Search PM
    Were both decks in the same noise reduction mode? In other words, both have to be in EDIT mode or out of EDIT mode for a valid comparison.
    Quote Quote  
  3. Member
    Join Date
    Jun 2017
    Location
    Australia
    Search Comp PM
    The only option that should really make a difference in either of these tests is the Y/C filter on the AG-MD835, however for some reason it's called something different. I could only find a NTSC version of the manual which states this setting is a Y/C filter, the first two tests on this unit compare the difference. The first test is the exact same config as the AG-5260 and the second config is using the S-Video with what I'm guessing is the Y/C filter. When I get a chance I'll check what it is called in the menu as I can't remember off of the top of my head. As for any sort of "Editing Mode" I don't believe either of these units have anything like that.

    For reference the AG-5260 has no configurable menu options, and like previously stated the only option that can be configured in the video signal for the AG-MD835 is the Y/C filter.

    EDIT - Where the Y/C filter is in the NTSC manual on the PAL unit is called "Notch", whatever that means. Also on that same menu is the "Edit Mode" option which has been set to off and all of the tests will have been done with that off.
    Last edited by Polsom; 15th Jul 2017 at 05:09. Reason: Added information
    Quote Quote  
  4. Member
    Join Date
    Mar 2021
    Location
    Boston
    Search Comp PM
    Originally Posted by Polsom View Post
    The only option that should really make a difference in either of these tests is the Y/C filter on the AG-MD835, however for some reason it's called something different. I could only find a NTSC version of the manual which states this setting is a Y/C filter, the first two tests on this unit compare the difference. The first test is the exact same config as the AG-5260 and the second config is using the S-Video with what I'm guessing is the Y/C filter. When I get a chance I'll check what it is called in the menu as I can't remember off of the top of my head. As for any sort of "Editing Mode" I don't believe either of these units have anything like that.

    For reference the AG-5260 has no configurable menu options, and like previously stated the only option that can be configured in the video signal for the AG-MD835 is the Y/C filter.

    EDIT - Where the Y/C filter is in the NTSC manual on the PAL unit is called "Notch", whatever that means. Also on that same menu is the "Edit Mode" option which has been set to off and all of the tests will have been done with that off.
    I know this is an old thread, but did you ever end up getting to the bottom of this? These units sparked my interest as well.

    I've wanted to get my hand on an NOS just to test it's capabilities. Those colors look completely washed out.
    Quote Quote  
  5. Member
    Join Date
    Jun 2017
    Location
    Australia
    Search Comp PM
    Originally Posted by BenKlesc View Post
    Originally Posted by Polsom View Post
    The only option that should really make a difference in either of these tests is the Y/C filter on the AG-MD835, however for some reason it's called something different. I could only find a NTSC version of the manual which states this setting is a Y/C filter, the first two tests on this unit compare the difference. The first test is the exact same config as the AG-5260 and the second config is using the S-Video with what I'm guessing is the Y/C filter. When I get a chance I'll check what it is called in the menu as I can't remember off of the top of my head. As for any sort of "Editing Mode" I don't believe either of these units have anything like that.

    For reference the AG-5260 has no configurable menu options, and like previously stated the only option that can be configured in the video signal for the AG-MD835 is the Y/C filter.

    EDIT - Where the Y/C filter is in the NTSC manual on the PAL unit is called "Notch", whatever that means. Also on that same menu is the "Edit Mode" option which has been set to off and all of the tests will have been done with that off.
    I know this is an old thread, but did you ever end up getting to the bottom of this? These units sparked my interest as well.

    I've wanted to get my hand on an NOS just to test it's capabilities. Those colors look completely washed out.
    I haven't. I pretty much wound up my interest in completing my Analogue conversion projects. That said I've still got my units set up, they've just sat and I haven't touched them since this post. I barely spent any time with the MD unit after discovering the poorer quality wasn't going to be of much use to me and I didn't have time to delve any deeper into it.

    If you come across a NOS though I would still grab it simply for the fine tracking control, being able to scrub through footage frame-by-frame on an Analogue scale is a rare feature of any VCR. I'd also say there is definitely an issue with my unit and I wouldn't expect an S-VHS capable player to perform substantially worse than an Older Panasonic unit of the same class.

    I have amassed a few more tapes that contain some unseen Analogue only footage, this along with the remainder of the other tapes I had left to convert that have just been left to deteriorate since, will hopefully get me interested in getting back into the project.
    Quote Quote  
  6. Member
    Join Date
    Mar 2021
    Location
    Boston
    Search Comp PM
    Originally Posted by Polsom View Post
    I haven't. I pretty much wound up my interest in completing my Analogue conversion projects. That said I've still got my units set up, they've just sat and I haven't touched them since this post. I barely spent any time with the MD unit after discovering the poorer quality wasn't going to be of much use to me and I didn't have time to delve any deeper into it.

    If you come across a NOS though I would still grab it simply for the fine tracking control, being able to scrub through footage frame-by-frame on an Analogue scale is a rare feature of any VCR. I'd also say there is definitely an issue with my unit and I wouldn't expect an S-VHS capable player to perform substantially worse than an Older Panasonic unit of the same class.

    I have amassed a few more tapes that contain some unseen Analogue only footage, this along with the remainder of the other tapes I had left to convert that have just been left to deteriorate since, will hopefully get me interested in getting back into the project.
    Interesting. That sounds odd too that it would perform worse. These medical units are intriguing and I know they get a lot of hate in this forum, but I like them for many reasons. Medical grade power supply and components built like a tank that are based on the pro units. Way more durable than a 1980. Integrated Frame TBC that saves me from having to buy an external TBC. Love the fine tune tracking controls. All my tapes are SP so not a problem. Plus parts for those units are a lot more common. You can't find NOS pro decks anywhere, but there are a ton of unused medical decks lying around for cheap. It's unfortunate that you couldn't get your unit to work up to the standards you would expect from an SVHS. I'm tempted to buy it but at the same time, I don't want to be stuck with an expensive pile of rubbish.
    Quote Quote  
  7. Member
    Join Date
    Mar 2021
    Location
    Boston
    Search Comp PM
    Originally Posted by Polsom View Post
    I have amassed a few more tapes that contain some unseen Analogue only footage, this along with the remainder of the other tapes I had left to convert that have just been left to deteriorate since, will hopefully get me interested in getting back into the project.
    If I do buy NOS, I may be interested in having you send me that tape you have screenshot if you still have it, and I'll take a capture on my machine to see if there is a major difference of the unit and post it on here. That would be cool.
    Quote Quote  
  8. Member
    Join Date
    Mar 2021
    Location
    Boston
    Search Comp PM
    I found some interesting info posted by your host Lord Smurf. He seems to indicate this can be caused by worn out heads.

    These medical units have all seen heavy use in hospitals. That's why I'm tempted to buy one that's never been used. I also know these Medical Panasonics circuits were based on the 7750 which has the vertical line issue on the overzealous TBC. I'm not sure if these would produce the same artifacts and Sony would be better, but it doesn't look to have the same chroma controls. However looking at your sample videos I'm not noticing any lines showing up in the image so that could only be an issue on the 7750.

    https://forum.videohelp.com/threads/319650-How-can-VHS-tape-color-loss-be-possible-%28-tape-fade-%29

    Originally Posted by lordsmurf View Post
    VHS data is color-under and stored as analog data, with color being derived from the chroma, which is played back by a VCR. The playback heads read the color under signal, and a poor relation here (due to head wear/debris or tape debris) also determine the color saturation (amount of chroma). The AGC/ACC/AFC is what keeps it from fluctuating. A messed up head/tape can result in loss of chroma. In other words, "color fade" is more a statement about a poor VCR than anything else.
    Last edited by BenKlesc; 15th Apr 2021 at 09:38.
    Quote Quote  
  9. Did you try enabling edit in the menu of the AG-MD? Looking at the service manual at least the PAL version of the AG-MD830 uses the same main video ics as the NV-HS1000 (but is otherwise very different), and that one has a tendency to have weak color when edit is not on (i.e noise reduction is active.) I don't know if it's something inherent to the NV-HS1000 or if it's to do with electronics going bad.

    EDIT: AG-MD835 seems to use pretty different digital video circuitry maybe akin to 7750 as mentioned and/or 1980p so maybe not. EDIT mode may make it clearer if it's not reading chroma well though. Weak chroma signal tends to result in more chroma noise.
    Last edited by oln; 15th Apr 2021 at 12:49.
    Quote Quote  
  10. Member dellsam34's Avatar
    Join Date
    Jan 2016
    Location
    Member Since 2005, Re-joined in 2016
    Search PM
    Originally Posted by BenKlesc View Post
    I found some interesting info posted by your host Lord Smurf. He seems to indicate this can be caused by worn out heads.

    These medical units have all seen heavy use in hospitals. That's why I'm tempted to buy one that's never been used. I also know these Medical Panasonics circuits were based on the 7750 which has the vertical line issue on the overzealous TBC. I'm not sure if these would produce the same artifacts and Sony would be better, but it doesn't look to have the same chroma controls. However looking at your sample videos I'm not noticing any lines showing up in the image so that could only be an issue on the 7750.
    That's not true at all, Worn or dirty heads will never fade the chroma signal, Chroma, luma and Hi-Fi audio signals are not recorded directly on tape, they are modulated in a high frequency signal or RF, A worn head will affect the RF signal and appear as white and black streaks that develop into noise bars if the head is completely shot or dirty, the same goes for Hi-Fi audio which is heard as static or complete drop outs.

    What will fade chroma though is a faulty or miss calibrated demodulator where the pure chroma signal got extracted or wrong setting.
    Quote Quote  
  11. Video Restorer lordsmurf's Avatar
    Join Date
    Jun 2003
    Location
    dFAQ.us/lordsmurf
    Search Comp PM
    Originally Posted by dellsam34 View Post
    Originally Posted by BenKlesc View Post
    I found some interesting info posted by your host Lord Smurf. He seems to indicate this can be caused by worn out heads.
    That's not true at all, Worn or dirty heads will never fade the chroma signal, Chroma, luma and Hi-Fi audio signals are not recorded directly on tape, they are modulated in a high frequency signal or RF, A worn head will affect the RF signal and appear as white and black streaks that develop into noise bars if the head is completely shot or dirty, the same goes for Hi-Fi audio which is heard as static or complete drop outs.
    What will fade chroma though is a faulty or miss calibrated demodulator where the pure chroma signal got extracted or wrong setting.
    Worn heads may not effect/cause it directly, but can affect it from an overall/holistic understanding. I've read quite a bit of VCR theory over the years, and it's complex stuff. As I was recently explaining in an AG-1980 thread, A affects B affects C. It's not always direct causations, but cumulative. Worn heads present as more than just streaks or noise bars.

    The larger context of that conversation is that VCRs are to blame for "tape fade", and not the BS about the tapes themselves "fading". The color data is always present, but merely needs competent persons and equipment to properly extract it. Apparently lots of huckster services are/were incompetent, which we already know/knew.

    Originally Posted by BenKlesc View Post
    I these Medical Panasonics
    I wouldn't get anywhere near those.

    Any claims of "NOS" are undoubtedly BS. From what I learned, those units were generally installed by a 3rd-party medical tech service, and hospital staff was trained on how to use those. These were never shipped in shiny new boxes to the hospital, and some local video/IT lackey forced to RTFM. I have friends that work in that sort of medical IT field (and IT includes basically anything electronic, not just compute).

    My opinion on the few results is that the AG-5260 has a far superior output, the colours appear to be much richer as well having an overall less noisy image.
    The old analog trick to remove chroma noise (red/blue mist) from tapes was to reduce saturation. In the medical field, misty stuff is not wanted, especially for things like hearts. So reduce the chroma. No mystery there. And then NR may not be desired in a medical setting.
    Last edited by lordsmurf; 16th Apr 2021 at 13:35.
    Quote Quote  
  12. Member
    Join Date
    Mar 2021
    Location
    Boston
    Search Comp PM
    [QUOTE=lordsmurf;2617129]
    Originally Posted by dellsam34 View Post
    I wouldn't get anywhere near those.
    Interesting. Thanks for the clarification. It's unfortunate the 1980's are so temperamental because that would be my "goto" unit. This has been my search for scouring the internet for the best of both worlds. A VCR that is built like a tank that will never die, but also with fine tune prosumer controls. It seems like every VCR made with TBC/DNR editing were designed to fail and need constant service to work properly and parts are non existent. I had originally thought pro units would have been made with better parts that were made to hold up longer and could take a beating but that is not the case. I've come to the realization there is nothing I can buy in the year 2021 that won't need a major overhaul. Perhaps I'm better off buying something like a nice Ensemble or Aja and shooting for a more reliable 1970 instead of looking for an all-in-one solution. No taking the easy way out if I want to build an archival studio. I don't think I'm willing to take a gamble on a $600 "medical" unit after reading this thread.
    Quote Quote  
  13. Member
    Join Date
    Mar 2021
    Location
    Boston
    Search Comp PM
    Here is the description off the original pamphlet.

    "Panasonic AG-MD835P video cassette recorder with built-in digital time base corrector (DBT), 3-dimensional noise reduction, auto head cleaning. The Panasonic AG-MD835P is designed to meet increasing need for high quality video and audio recording/playback in the field of medicine. Advanced features like built-in TBC, DNR and 3-D Y/C Seperation circuitry help achieve the exceptional picture quality required for precise image analysis. The Panasonic AG-MD835P is classified by Underwriters Laboratories Inc. as to medical electrical equipment with respect to electric shock, fire and mechanical hazards only in accordance with UL 2601-1, Control number 76KA."
    Quote Quote  



Similar Threads