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<DIV>TBC's are an interesting lot. The Quad ones were all analog until the
AVR 2 and 3. There are advantages to the use of the analog type of
TBC. </DIV>
<DIV> </DIV>
<DIV>The video never is subject to the conversion to digital and back. The
conversion was not of a high quality in the early units. Even the AVR 2
had issues and you had to tweak the converter to eliminate stepping.</DIV>
<DIV> </DIV>
<DIV>The AMTEC and Colortec are a very stable unit. The experience that I
had was that they never needed to be looked at. I would do it anyway about
once a year and never found them to be a problem.</DIV>
<DIV> </DIV>
<DIV>The Velocity Compensator was the secret to a good playback. It
integrated the errors over a head pass and thus made the color hue constant
across the length of a line.</DIV>
<DIV> </DIV>
<DIV>Now what about a TBC. Merlin was able to make several units
work. Yes you get a very wide window. If the tape could not be H
locked, then there was a problem that the analog TBC could not handle.
(Unless you had an AVR 1.) Most after market digital TBC's can not
handle segmented scan and the head switch. This sudden jump in a line
placement is not what a TBC sees in every day life. The result is usually
a displacement of the line. There is usually a loop circuit to smooth out
the errors over several lines. That is the reason for the displacement.
</DIV>
<DIV> </DIV>
<DIV>Most TBC's of the era were only 8 bit so the conversion is not as clean as
a 10 bit. I could walk up to an AVR 2 and see when the TBC needed
adjustment because of the artifacts that 8 bit put in. Just feed a ramp in
and it becomes very easy to spot. </DIV>
<DIV> </DIV>
<DIV>Would I change out the analog units? My answer is no as I do not see
that there are going to be any better results. The proper setup of the
original machine is the secret of a good playback. </DIV>
<DIV> </DIV>
<DIV>Now for a possibility to play back the REALLY TERRIBLE tape. The
machine can be played back in many different lock modes. If you can not
obtain H lock, what about taking the output of the AMTEC and then feeding that
to a TBC? Play the tape in any lock mode. The AMTEC takes care of
the segmented scan and any guide errors. Let a TBC external bring the
picture back into color and H lock. Velocity errors might be an issue
because the AMTEC might not have the error integration across the line.
Any thoughts or has someone tried this?</DIV>
<DIV> </DIV>
<DIV>Chris Hill</DIV>
<DIV>WA8IGN</DIV></FONT></BODY></HTML>