Did I damage my VCR heads?
 

Hello folks,

I've been converting some old family videos from VHS to something digital.

After I converted ~5 hours of tapes, I thought the image was looking a little smeared/blurry compared to when I started, so I tried to clean the tape heads with some paper and some 91% Isopropyl alcohol. The first youtube video I looked at showed a bad technique and I'm afraid I may have damaged the heads on my VCR.

I have a JVC HR-S7800U.

Here's a picture before I did before the cleaning

Attachment 11127

and here is afterwards. The bottom left corner is always has that black spot (it moves slightly horizontally, but not vertically) and those bottom lines are always off.

Attachment 11128

This picture shows the bottom being "off" the best.

Attachment 11129

Did I destroy my VCR?

Thanks!

Tim

The heads scan the fields from top to bottom, if the heads are bad it will spread all over the video frame, What it might have happened is miss alignment of the tape guides, While cleaning you may have moved one of the P guides, make sure they are not loose, if they are loose then that's definitely it.

No, not at all destroyed.

Have you tried with a different tape...? Have you checked the tape for edge curling or similar...? If the tape is damaged where the control track is you're going to have tracking problems.

If the exit guide pole has become loose, causing the alignment problems, make some readjustments to lock it in place.

Don't trust YT for technical advice. That's one of the worst sources of information...

Thanks for all of the advice!

Yep, I've tried different tapes, and they all have the same black splotch on the bottom left (on my SVHS tapes, the black splotch is on the bottom right).

Do folks have a good diagram of the inner-workings of the VCR? I'm looking at this, and the terminology used here doesn't quite line up with what's being used here.

https://www.repairfaq.org/sam/vcrxprt.gif

There wasn't anything obviously loose... the whole TakeUp piece is much looser than the Supply Side piece when a tape isn't in the VCR, but when a tape is in, both feel solidly locked in place.

I could loosen/tighten the takeup side roller guide, but that only seemed to make things worse... I would get bad "tracking" lines on the bottom of the screen, but the black area would remain.

Interestingly enough, when I rewind the tape, the black area goes away (fast forwarding, the black area is still there). From what I've read, issues on the bottom of the screen seem related to the takeup side of things, so it seems like you've got me on the right track.

Anything specifically I should be looking for when the tape is going through? Is it safe to adjust the takeup roller guide when a tape is playing (I've been ejecting the tape, turning it <1/8 of a turn, putting the tape back in, and see what difference it made).

What's a P guide? Is that one of the guide posts?

Thanks for your help!

Tim

No man, You adjust the tape while it's playing, The fact that you confirmed that P guides are loose as I expected, the alignment may have been severely off, I would suggest to learn how to do it properly, you may get one tape working properly but other tapes don't, The best way of doing this correctly is with an alignment tape and an oscilloscope, I would never use a VCR for capturing that was aligned from random video tapes. But that's me.

Doing it while the tape is playing seems to make a ton more sense. :)

Looks like I'll need to get a security bit to turn the guide... I was using my fingers before, but with a tape around it, I doubt I'll be able to get my fingers around it.

I'm not sure if the P guide was really loose... they slide on a track when a tape is inserted, and once they are in that position, they don't seem loose at all. Maybe I'm misunderstanding what you're saying though.

I'll let you know how things go when I adjust it while playing a tape.

I agree, doing it with a random tape seems pretty arbitrary and there is no way I can get it super accurate. Hopefully I can get that black blob to go away, and then see how other tapes play with that setting.

Tim

Eh. Just go to the local dollar store, hardware store, get a small cheap flat head screwdriver. Then dremel it. That'll work fine on most JVC decks. A few can just use a small flat head, period.

You must be extremely careful, one little slip and you could either rip the tape, or damage the heads. Or maybe mess up something else. Breathe, concentrate, pretend you're a surgeon. Because you actually kind of are performing open-heart surgery on a VCR!

It's "head-switching noise" = skew after the head switch point.

What the hell are the screenshots, even? 720x540 with some player deinterlacing turned on, who knows what other processing.

"Before" appears to have TBC turned off while "After" appears to have it turned on.
"Before" top & bottom have half-lines and black masking or blanking.

And there's almost no detail in the images. Tell me these are some sort of copies, not camera originals.

You have precision kits on Amazon for $5-$10 (ship to your door). A small flat head should do the job. Start adjusting the exit guide (P3) and see how it goes... But if you want to do it properly, you should rely on an oscilloscope.

Something to remember is that scoping the signal is simply setting it an some sort of altruistic best. However, the tapes may not be in that "best" range. So aligning to tapes isn't necessarily bad, especially if this is being done for your own personal tape sources. (Noting that the alignment may be bad for the next the person, and this whole process must then be repeated).

I don't know that I'd worry about overscan area noise. This is all within a sensible 10px mask all around.

BTW, took closely at the sample images in the first post. The line at bottom is "bigger" because the image shifted upwards for a few lines.

Panasonic, with scope

If that's his main/best deck, it's better to keep alignment within specs. That's what alignment tapes are for. If you need to make some tweaking later on with a tape that has been recorded with a misaligned vcr/camera, use a secondary VCR. I have some vcr's for this purpose... I wouldn't touch any of my high end decks for this. Same as you I guess... I don't see you playing with the alignment on your best AG-1080's. Am I wrong...?

This is precisely what I do. :salute:

I have use SR-V101s specifically for "breaking" alignment as needed.

BTW, the reason for that model is
- lighter, smaller, set in lap to tweak AND watch monitor at same time
- light to lug around, pull out only when needed
- larger guides easier to make slighter tweaks
- simple small flat head is adequate
- plastic lid chassis easy to open, don't need to screw down

It's not my favorite general-use model (though sometimes copies an actually A+/A++, as mine are), but for this purpose it's very easy. It's generally a B+/A- type of deck, plastic, gets quicker wear, looser transport tolerances, so you also have to find a good V101, not just any V101.

Trying to realign an AG-1980 would be punishment. :laugh:

Thanks for all of the tips and links. I'm hoping this weekend I can get/make a tool to try this out.

To answer some of the questions (in case there is a better way I can be doing this).

It's interesting that the screenshots I'm taking (using both VLC and MPC-HC) are giving me 720x540 images from my 720x480 video captures.

I'm capturing these using the S-Video Out to a DV encoding box, and then firewire to my PC. The screenshots I shared came from a straight conversion to H.264 without using any filters. It's my understanding I'm losing some chroma data with the initial DV encoding, and so I purchased an Intensity Pro 4k to grab the raw video instead, but I kept getting video dropouts going that route. The DV box (ADVC-100) always seems to give me a solid signal.

Sadly, these aren't copies... they are camera originals. I guess that's what you get with a consumer video camera in the late 80s recording on EP mode on poorly stored tapes. I haven't looked into any filters yet to make things better... I'm assuming things aren't going to get dramatically better (garbage in/garbage out).

I looked up "head switching noise", and you're absolutely right... it looks the same. The web seems to indicate this is "normal"... but I didn't see it before I cleaned the heads, so why would it rear its head now? (no pun intended)

Thanks for the links to the YouTube video. It seems like this is trivial to do with a scope. I like the idea of being able to set it perfectly, but even used scopes look to run $100+. :(

Wish me luck this weekend. Hopefully I can get these cleared up and get back to capturing tapes.

Thanks everybody for your input and help!

Tim

-- merged --

I used the dremel on a screwdriver bit I had, and used that to turn the screws. Pretty simple/straightforward.

I was able to clear up the tracking noise, but that "head-switching noise" remained. I'm starting to drive myself nuts, as I didn't seem to have that noise before. I tried a different VCR and the head-switching noise was there too, so now I'm thoroughly confused. You're right, I can mask it out, but now I'm really curious what happened.

Semi-unrelated question related to using a scope to align a VCR. I noticed you can get USB-based scopes for $60. Is there something special about alignment tapes to get the signal on the scope?

Thanks!

Tim

Is this the units? https://www.amazon.com/Hantek-HT6022...language=en_US

If so, only $60, small/compact, looks interesting for that reason alone.

But how well does it work?
And are you ready to dive into learning how to use it? It has a learning curve, and can be art as much as science on application/usage.

No; in those 12voltvids YouTube videos he isn't using actual alignment tapes. He hooks up one probe to the PB RF test point and the other to the Head Switch test point as the 30Hz trigger.

It's possible to adjust the head switching point on VCRs, I don't know what would cause it to change on it's own though. Only time I've seen it change is when I was swapping mechanisms between two Samsung VCRs. On older VCRs it's usually done by adjusting a potentiometer somewhere, on panasonics it's labelled "PG Shifter". On newer ones like your JVC, the head switch (and most other things) is set by an IC, and there's usually some service mode setting to auto-adjust it. On newer JVCs you need a special service remote (or to emulate it) to do it though, while on other brands it's often just some special key combination or a hidden button that's used to access service mode.

An alignment tape will have color bars and test tones recorded with perfect alignment. A commercial tape will usually do fine for alignment, though it won't be in EP/LP/SLP which an alignment tape may have, for extra precise adjustment.

What would not be as easy with just a commercial tape would be other adjustments (especially on older VCRs) like fine-tuning deemphasis, analog noise reduction and other bits of the decoding path. Those things normally don't drift on their own though so it's not something one has to worry about.