Modding a regular VHS VCR to output S-Video?

[ChiDragon]

Continuing a discussion from another thread (http://forum.doom9.org/showthread.php?p=1696088#post1696088), where my interlocutor judged it was off-topic.

Recapping...
everyone can modify already own VCR without S-Video and add S-Video output.
I eagerly await your step-by-step instructions for how to modify each of my VHS machines. (Not sarcasm.) All I know is that there are "test points" and soldering involved.

I was asked for a list of my VCRs:
Magnavox VR9960AT01
Sony SLV-585HF
Sony SLV-779HF
Sharp VC-H9888U
Panasonic PV-V4524S
JVC HR-J693U
At first i was able to download service manual for Sharp VC-H9888U - Y signal is available at pin 52 IC201 (IC201 HA8311AF - no datasheet is available on internet - as usual in case of Japanese custom electronic) and on connector P208 (pin 1), C signal is available at pin 55 IC201 and on connector P209 (pin 2).
Based on block diagram those signals are combined in circuitry (part of Gamma Circuitry) made from Q551, Q552, Q271, Q272, Q274 to create CVBS.

My next question: what do I do with this information?

[foxyshadis]

You'd want a jack like this (http://www.amazon.com/Hubbell-Wiring-Systems-SFSV110AL-Punch-Down/dp/B00IS2TSJG) (just an example, you can also get bare connectors you have to solder to) plus a few wires or even a spare phone line, and then solder the correct wires down to the exposed pins on the listed chips. You'll need to find a ground too, but that's usually the easiest part, there's always lots of them. Here's the S-video wiring diagram:

https://www.dropbox.com/sc/fra6i4ftigbqddo/AAAwRljU_869AqE-fOhh38xla/0?dl=1

[pandy]

My next question: what do I do with this information?

Hmm do you expect me to pay xxx $ for Canada visa, then buy ticket to fly Canada (few 100's $), then some retard at border will return me to Europe?

Not my circus and not monkeys - find someone with head on neck that can make modification for You or don't ask trying to prove something (i'm not VCR collector) - life is full of opportunities (but i assume you already own few S-Video capable VCR and you are not interested in modifications).

[Ghitulescu]

My next question: what do I do with this information?

Well, identify the Y and C output pins. Then do a buffering stage (using RF transistors or dedicated OAs) and use the VHS as an S-VHS deck for VHS tapes.

This is now rather moot, as many S-VHS decks are found for peanuts (not on eBay though), yet for the versed electronist a nice project.

[ChiDragon]

find someone with head on neck that can make modification for You
First it was "everyone can do this", now it's "you're an idiot if you don't already know how to do this"?

Well, identify the Y and C output pins. Then do a buffering stage (using RF transistors or dedicated OAs)
Does that mean the output can't be directly connected to the pins as foxyshadis suggested?

[Ghitulescu]

Does that mean the output can't be directly connected to the pins as foxyshadis suggested?

Yes to the question, no as an answer :) .

You can get the signals directly, only if the IC has buffering. If it doesn't then the cumulative impedance of the whole block what comes after IC (inside cables, solderings, plugs-contacts, and input circuitry) would case in the best case high frequencies damping, in the worst even the destruction of the IC, passing by asynchs and interferences.

[pandy]

First it was "everyone can do this", now it's "you're an idiot if you don't already know how to do this"?


Nope - as your question has nothing with "don't know" - this part of conversation we had on different site about perfect S-Video to CVBS conversion where You disagree to name lossless conversion S-Video to CVBS if CVBS to S-Video can't be done in a lossless way. Currently it is only You ego trying to pin me up when i'm saying that as a principle for VHS (and similar system is to store separate Y and C signal) there possibility to have separate Y and C at output (S-Video).
So You are not idiot but for sure you are trying to prove that im wrong.


Does that mean the output can't be directly connected to the pins as foxyshadis suggested?

It depends but it is wise to use buffer always where it is possible as you can't predict way how device behave in different situations (such as shortcut for a brief moment signal to ground etc) - buffer gives desired separation.

Hope it is clear now.

Modification is possible to everyone - directly or indirectly.

[ChiDragon]

Currently it is only You ego trying to pin me up when i'm saying that as a principle for VHS (and similar system is to store separate Y and C signal) there possibility to have separate Y and C at output (S-Video). So You are not idiot but for sure you are trying to prove that im wrong.
I disagree that it's possible for everyone to do it, but I'm not trying to prove you wrong. I'm hoping you can show that I'm wrong by providing instructions that someone like me without a background in electronics can follow. (And/or point to resources that can be used as a primer for the skills required.)

It isn't just out of curiosity at this point. The practical application is that I haven't yet found a S-VHS machine that outputs an image I'm pleased with for my EP tapes. A couple of the VHS models look better to me, but suffer from added dot crawl and rainbows even with a 3D comb filter.

[2Bdecided]

many S-VHS decks are found for peanutsIn Germany maybe. I understand they were quite popular over there. Finding decent working S-VHS machines in the UK is surprisingly expensive. The best ones now cost more than they did when new.

Cheers,
David.

[Ghitulescu]

In Germany maybe. I understand they were quite popular over there. Finding decent working S-VHS machines in the UK is surprisingly expensive. The best ones now cost more than they did when new.

Apparently, if one uses eBay as a reference, indeed, the prices went up, and this for some time. It's the analogue revival, you know, vinyl and turntables, compact cassettes, open-reel (reel-to-reel), and why not VHS and stuff.

But one may be in luck at a local flea-market.

[2Bdecided]

It's got nothing to do with "the analogue revival" and everything to do with people wanting to copy their old tapes before they dump them. That's kind of the opposite of an analogue revival! ;)

The chances of finding an S-VHS machine "in the wild" in the UK are vanishingly small. True, you might be in luck, but it's rare.

Cheers,
David.