Wobbly/Out of phase VHS audio-Caused by tension error?

[Belmont]

Recently, my Sony SLV-679HF has had trouble with EP tapes with linear audio. The audio is distorted, especially during high frequency/amplitude sounds, such as someone talking loudly, that coin sound in the NES Super Mario Bros, a woman screaming, loud horns or strings, etc. Sometimes, it'll alleviate after a minute or so, and I can rewind to the starting point to begin capturing. However, on some tapes it doesn't let up. I opened up the VCR to find and pinpoint exactly where the problem was. It appears that the back tension arm has gone out of adjustment, causing the tape to flutter before it reaches the video head (the little area between the erase head and the supply guide). It only seems to happen on EP speed tapes. SP and LP play fine, both in hifi and in linear modes. However, while EP Hifi tapes also have this flutter in that area, there is no audible distortion. Since it appears to be a problem with the backtension arm, is there a way to fix this without permanently damaging the machine?

If I'm not being terribly coherent about this, I'll include some videos that illustrate the problem.

[Belmont]

Anybody? Hhheeeelllllllllllloooooooo?

(*crickets chirp*)

[admin]

We're here.

In terms of repairing that specific unit's hardware -- I don't really know. I'd have to spend some time reading through a repair manual. Even if it's not the exact repair manual for this specific model, manuals in general can sometimes tell you all that's needed. After all, VCRs are mass-produced commodity products (even the pro decks) with many similarities.

The MP4 has substantial horizontal signal jitter. It's so bad as to be a vibration of the image. An internal TBC would fix that. Even certain DVD recorders as pass-through may fix that.

I don't hear any distortion in the MPG audio. What I do hear is a lot of hiss, fuzz and gurgles -- and that can be removed, leaving just the good audio.

The MP4 audio's gain is too high. Reduce it with a mixer before digital conversion input. The distortion only happens at loud volume peaks. (There's really nothing that can be done to fix this in software, but I think you already know that.)

This is all fairly standard stuff, nothing too unusual here.

[Belmont]

Ah, merci beaucoup.

Here's what's odd. The distortion on the .mp4 seems to only happen with this VCR. I ripped the same scene just a month or so ago with the Panasonic, and as you can hear, the only distortion is the usual VHS hiss and muffledness. This rules out a problem with the tape or the recording, but it appears to be a problem with the deck. I'll get around to fiddling with the machine later. It could just be a buildup of dirt prevent the tape from getting proper tension, or the A/C head has somehow been knocked out of adjustment (problems started after I lent it to a friend for a week). Are these things I can use a service manual for to get precise adjustments for, or is it a process of playing by ear and trial & error?

As for audio level, there is a bit of clipping, but this is more than likely due to my card. From what I can gather from family photos taken in the living room, the cable ran through the Sony Super-Beta Hifi machine and into the '80s JVC. It is likely that the audio level was raised too high with the level slider thing. Then again, there isn't much distortion audio-wise with the Panasonic rip. I'm going for the A/C head being maladjusted, because that would cause audio distortion and timebase errors, right?

The warble isn't as obvious on the MPG, but if you listen to the beginning and the end, it's there. That's where I first noticed it. The problems becoming more and more frequent, and quite frankly, I'd much rather have the Panasonic with the nasty tracking back :\