[QuadList] Rebuilding RCA TR-600s

Tue Sep 8 10:47:02 CDT 2009

Dear Quadlist:

Oh what fun it has been.

It has been awhile since I’ve updated anyone here about our rebuilding the
RCA TR-600 machines we have.  It is taking a while because we can not devote
full time to this project.  But it is interesting and I am learning a lot
about the operation of these machines.

These systems started out in pretty rough condition.  I swear when we
cleaned them, we got pounds of dust, dirt, tape trimmings and other junk out
of the machine (ok
maybe pounds is exaggerating a bit
but it was a lot).  

We are almost at the point of having one of the machines up and running
(yesterday was quite frustrating
more in a moment).  We picked what we felt
was the better of the two whole machines (we have a third for parts).  This
one had lower hours compared to the other machine and it would at least
power up (including the head wheel and capstan) and would pull tape.  We
were not able (at first) to get any true video signal, as it just wasn’t
locking up.  After pulling all the boards, cleaning all the contacts and
reseating everything, we were at least able to see video, although color
wasn’t locking (in other words, even color videos played in B&W).  We
checked power supplies and looked for any obvious things (broken wires,
burned caps/resistors/boards, etc).  After a thorough cleaning, we started
fine tuning the machine.

Last week, we started going through the alignment procedure.  Wow
what a lot
of adjustments.  A lot different than today’s machines.  I’m only acting as
the assistant here (ok
really a go-fer
but what the heck
I’m learning).  Our
engineer has a better idea of what is going on with the machines, so some of
my explanations may seem a bit light, technically.

First step was alignment and EQ.  We got this looking pretty good.  What we
found is that many of the adjustments were close, but a couple were off by
quite a bit.  After going through the alignment, we made the TBC
adjustments
color is looking better at this point, but still getting banding
and drop outs in the video.  Horizontal phase is not working at this point
(knob turns, but it doesn’t do anything).

After TBC adjustments, we went through the drop out compensator and got it
adjusted properly.  At this point, the video is looking really good
actually
surprisingly so.  Everything seems to be working properly.  Horizontal phase
is now working.

Now keep in mind that the whole time we are doing this, we are doing so with
the back off the machine, because we are looking at adjustments on the front
of the machine (cards in the nest) and looking at wiring on the back of the
machine to make sure everything is connected as it should be.  At this point
(yesterday about lunch time), we are feeling pretty good.  Good enough to
button up the back to make sure the cooling works on the machines as it is
designed to.  So, we put everything back together (all the panels and
guards) and roll the machine back into its place.  

Once this is done, we want to just try one last test.  I load up a tape,
which turns out to be B&W.  It looks pretty good (no burst, because it is
B&W), but it still looks good.  So we decide to put up the color tape we
were working with and it looks like absolute garbage
what the heck???  The
output video looked really bad when playing a color tape
lots of
banding
video taking a long time to lock up (we had it locking up in about 1
second
now it was back to several seconds
probably 5-10 seconds), horizontal
phase is no longer working, etc.  This is the same exact tape we saw play
great ½ hour ago.

Here is the situation.  We were not able to see output video by using the
top switcher (we always were able to see demod and TBC
but not output).  We
ended up changing that switch (which is just a manual switch).  In order to
see output video, we physically had to route the cables to the TV
monitor
but we wanted to be able to switch the video so everything could be
done from in front of the machine.  I can’t believe this had anything to do
with the output video going from good to bad
since this is only a manual
switch
but who knows.  Talk about frustrating
here we are, seeing really
good looking video, thinking we are ready to go, only to have a setback like
this.

So here is our present situation.  We worked on it a little more yesterday.
We found that some of the boards in the “C” row might not have been seated
completely.  We got it to the point where we are able to get video to lock
up, but there is still a significant delay with the video output (the video
is shifted to the right side of the TV monitor screen and we can’t seem to
adjust this at this point).  Our next step will be to go through the TBC
adjustment (alignment) again.

But at least we got to see the machine make really nice pictures for a
little while (so we know it can)

There are a couple of things that are strange
when looking at demod and TBC
video on an oscilloscope, we see one synch and one burst signal
but when
looking at video output, we see two
and one is in the wrong place (I can’t
remember if we had the system in regen or house mode when seeing this
I
think maybe in regen).  Note that we are feeding a black burst signal into
the machine from an external generator.  This seems to be a timing issue,
but I would be interested in hearing input from others on the Quad list if
they’ve experienced anything like this in the past.  Alignment may solve
this problem
but if anyone has any thoughts or ideas, I’d appreciate them. 

Another, possible related issue is that if we feed bars to the machine and
it is in regen mode, the video signal drifts (as seen on both the TV monitor
and waveform) and the video is in B&W.  If we switch to house mode, this
clears up immediately (color bars are now in color and rock steady
note
color bars are from a synch/color bar generator
not an outside tape source).
The color bar generator is genlocked to the black burst generator feeding
the machine.  Terminations are correct (we checked).  Strange

Another is the tension on the reels
we are playing a ½ hour tape and it
seems as if the mass of the reel is too much for the system to overcome (we
have to continually adjust the tension to compensate for this).  I have
spare reel motors, but don’t want to get into replacing these unless we
absolutely have to.  We have not put a spring scale on the reel motors
yet
that will be our next step.  Along with the tension problem, we have a
buzzing (intermittent) that appears to be from one of the solenoids on one
of the reel motors (supply reel).  This comes and goes
not sure if it is
related to the tension problem or not.

Once we get the first system working, on to the second system.  We’re close
on the first system
we’ll keep you posted on progress.

A couple of things learned

1.       A magnifying glass would be a great help when locating test points.
Fortunately, we have a second set of boards we can look at to help with
this.

2.       A short tweaker is a must (you just can’t get at some of the
adjustments with a long one).

3.       When 2” video looks good, it looks really good, but it can go bad
in a hurry.

4.       I have a new-found respect for the engineers who kept these things
running.

5.       A second extender card can make your life a lot easier.

6.       A short chair is a necessity
knee pads would be nice (ok
just
kidding)

7.       Supply reels and take up reels of different sizes cause problems.

8.       Thank goodness for manuals
even if they aren’t that well written.
You couldn’t do this without them.  More pictures would be nice (of the
oscilloscope, demonstrating what the signal is supposed to look like
just
for confirmation). 

Thanks;

John Walko

Media Archive Manager

Scene Savers

www.scenesavers.com

800-978-3445

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