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08-08-2019, 11:36 PM
ofesad ofesad is offline
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Hi people. Marcelo here from Argentina.

One of my backup AG4700's has develop'd some issues of jittering (horizontal shaking) and a some weird audio issue too. (Deck PANA2)

Other has some noisy picture. (Deck PANA1)

The third one is for reference, it's my main capture deck. (Deck PANA3)

I attached some captures with these decks.

Deck settings: Built in TBC is OFF and AI is OFF

I haven't done a proper set up of PANA1 and PANA2 yet, but I'd like your input on what to check before going into the board and star messing with the pots and stuff.

Also will be measuring all the trimpots and variable resistors values of PANA3 for future reference.

Any help, comment or wild guess is welcome!


--merged --

I forgot to mention that all the Deck's are AG4700's. The only difference between Deck 1 and 2 against 3 is the head. (I Made a post about'em).

Attached Files
File Type: avi PANA1_TBC_OFF_SONY_CUT.avi (34.30 MB, 21 downloads)
File Type: avi PANA2_TBC_OFF_SONY_CUT.avi (34.59 MB, 17 downloads)
File Type: avi PANA3_TBC_OFF_SONY_CUT.avi (35.17 MB, 16 downloads)
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08-13-2019, 02:05 PM
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Caps is always the likely culprit on Panasonic S-VHS decks.

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08-15-2019, 10:31 AM
keaton keaton is offline
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I think it is best to always caveat what I'm about to say with, don't pursue this option 1.) haphazardly , 2.) before you have sufficient data to suggest it could be an issue, and 3.) unless you are totally comfortable with doing so, accept responsibility for what you are about to do with understanding that it can be a delicate matter. So, having said all of this, now I can proceed.

If you are electrically knowledgeable, certainly investigate that route as much as you can first. I have not tried it, but have seen folks on youtube with meters that check capacitors to see if they are in spec. Doing all of this first would seem wise, if you have the knowledge/skills. Although, I've heard some Panasonic (namely the 1980) models can have some pretty advanced capacitor designs that is best left to professionals. Not sure how complex yours is.

If you don't find anything wrong electrically, or if you think you may have an issue with player alignment, then perhaps try some adjustment of one or both guide post(s) by the video head, and possibly the audio/control head as well.

I am not wise enough to check electrically. However, I have received a deck that was enough out of alignment, that I had to do some adjusting of the guide posts by the video heads, as well as the audio/control head. I realized this because there was a lot of issue such as crackling hifi audio (which is from the video head), horizontal jitter of image. It is certainly wise to do some learning on this, and get a service manual if you can, before jumping in. Also a wise idea, is to remember the starting position of any screw you adjust, and to adjust very slowly one at a time (returning to original position if no improvement occurs), not straying too far from the original position. If you do find improvement with the video path (video jitter goes away and no hifi audio issues), you may then have to check that the linear audio is good, and use a similar approach to carefully tweak the a/c head. Adjust the height of the tape coming off the video drum can effect the height of the tape traveling across the a/c head. Also, the A/C head could cause bad video if the control track part of the tape is not aligned to the a/c head. But that would seem like a more serious alignment issue.

SP tapes are used for "coarse" alignment of things. Once that's good, progress to EP tapes to "fine" adjust things, since the video track is narrower and thus requires a tighter alignment tolerance. If you have a scope, and a service manual to show you the test points, that is ideal. I think the 12voltvids youtube channel has some videos showing what a scope looks like when path is aligned vs not. There are probably other places as well. I would think the service manual would also show such a diagram. However, it is not needed. Using a monitor and decent audio equipment can be enough to use your eyes and ears as to when the audio and video is best. Of course, the tapes should be pre-recorded from a studio, as they are most likely to have been made from calibrated/aligned equipment. It is wise to not adjust the player because you have a bad tape(s).

Also consider if tracking adjustment can solve all of this before going down any path involving alignment changes.

So, again, I will say that this is a possibility as to why symptoms with audio and video stability can occur. However, it may not be an issue at all. It all depends on how much you have researched in advance to try and deduce the likelihood that this is a serious possibility. You should see the symptoms with a lot of tapes, and not see them on a known good deck.

I'm not sure how likely it is that this has suddenly just happened to a deck. Usually alignment issues have occurred over longer periods of time or due to some heavy shaking of the unit, perhaps from shipping. I thought the Panasonics were better at not going out of alignment, compared to say a JVC, which is the one I had to make adjustment to after it was shipped.

So, it's just a possibility. But it is solely up to you to be cautious and only pursue this when you feel confident and comfortable in doing so. You don't want to do something that could make things worse, before you have exhausted other options.

Best of luck to you.
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08-15-2019, 11:11 AM
hodgey hodgey is offline
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I do not think this is about alignment, as that typically result in noise on the top or bottom of the picture, not at completely random spots. The noise could be that the video heads have picked up some dirt, at least our NV-HS1000 tends to get dirty heads very very easily, a lot more so than any other deck I've used.

The jitter may be due to something causing the capstan (that drags the tape around) speed to be unstable. Thats a bit above my level of expertise to debug, could be bad caps or some adjustment, I don't know. I notice the head switch point seems slightly lower on the PANA2 compared to the other ones as well, maybe that's related. (Can be adjusted with the PG Shifter pot.) Otherwise the PANA2 one does seem to have the noise spots the other two have.

I know bad head grounding can some times cause white spots, not sure if they look quite like this thoough, so you could maybe try to clean the top of the video drum under the carbon brush (black thing that is pressed onto the top of the head) and make sure it makes contact to see if that helps.
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ag4700, audio, hs1000, jitter, panasonic

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