convert VHS to DVD

[Gene Heskett]

On Wednesday 14 March 2007, Tim wrote:
>On Tue, 2007-03-13 at 10:40 -0500, Styma, Robert E (Robert) wrote:
>> I have a set of Video Tapes (reel to reel) which go
>> in a Sony Video Tape Recorder.
>
>I've still got a few of those.  One or two of them even play back,
>still...
>
>> I got the machine working smoothly enough, but cannot get a stable
>> signal out of the box.  I tried both the RF output and the video
>> outputs.  I would like to get the tapes transferred to digital media
>> or at least VHS before they deteriorate too much.  They are mostly
>> 1970's vintage.
>
>You want to use the video output.  The RF output, on those decks, could
>be one of two things:
>
>A TV channel, which is further encoding of the video signal, and you'd
>need to decode back to video to record.  You're adding more signal
>processing to the path, that wants to be avoided, particularly since
>they usually had a quite poor RF modulator.
>
>The FM signal directly from the video heads, which is only useful for a
>machine to machine dub, and that's two machines of the same model.
>
>> Do you thing a Time Base Corrector of the sort you can find on ebay
>> would have a chance of correcting this situlation?
>
>Possibly...  It depends on various things, and what the "stability"
>problem is.  A time base corrector can take out minor jitter, quite
>okay.  But you'll be hard pressed to fix up servo hunting or tape wow
>(that's a continual moderate to slow motor speed changing).  You may
>find some timebase correctors will not handle poor sources, at all,
>whether that be down to lots of noise or excessive time base errors, or
>other reasons.  You could only try it to see.  You'd probably need to
>get a full-frame TBC, not just something like a 16-line one, unless your
>VTR will lock up to external sync during playback.

At those machines ages, and speaking as a tech, I would be quite sure to 
get out a magnifying glass and see if the edge of the tape is being 
distorted as it goes through the guides on either side of the drum.  The 
rubber in the pinch rollers tended to swell from migrating lubricant 
coming out of the rollers bearings, which in turn made it pull one edge 
of the tape harder than the other, and that pulled it off the path, 
causing edge damage to the tape, and large dropouts in the signal due to 
miss-tracking during the vertical interval, or just before, depending on 
which edge of the tape is being distorted. So find yourself an old, gray 
haired broadcast engineer who needs a half gallon of Jack and a $100 
bill, and let him see what he can do to alleviate the problem.  And hang 
onto the Jack till he's done :). That bright kid of only 27 down the 
block will be clueless, so go find an old fart like me, who once worked 
on such as this.

Those rollers by now are made out of absolutely 100% pure unobtainium and 
I have even gone so far as to run a close fitting bolt through the 
bearings so that the roller can spin freely, sticking the whole thing in 
my small 7x12 lathe, and swing past it with a cutoff wheel in a dremel 
grinder mounted in the toolpost, touching it just enough to clean up the 
surfaces, letting the dremel spin it by having the face of the cutoff 
wheel touch it at maybe a 10 degree down angle, eg the dremel is way 
under center so the edge of the wheel just covers the center of the 
contact area, with it just enough off a straight right angle by setting 
the rear of the grinder a few degrees to the right of dead on so the 
wheel brushes past the rubber mostly to the right, and slightly downward 
just enough to make the roller spin.  You may have to help it spin 
occasionally.  The lathe only serves as a mount, do not turn the spindle 
on else the eccentricity of the bolt will be imprinted into the rubber, a 
very undesirable thing.

This all assumes the pinch roller has ball bearings.  Not all do.  If it 
has a bronze/oilite bushing, you are probably hosed as you'd wear out the 
bushing with the above operation unless you had a shaft for it to spin on 
that was made at that exact size, and from that _exact_ steel formula.  
It would also need a refreshing of the oil soaked into the bushing, say 
about the amount that will hang onto the end of a round toothpick, and no 
more.  Put it into the center of the bushing and let it migrate at its 
own speed to the ends for a few hours before the grinding operation is 
attempted.

After that, a tbc may not be required, but it would be a good idea anyway.

>--
>(This box runs FC6, my others run FC4 & FC5, in case that's
> important to the thread.)
>
>Don't send private replies to my address, the mailbox is ignored.
>I read messages from the public lists.



-- 
Cheers, Gene
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