JVC Mini DV camera Tape problem

[Ulrik Smed]

Hi

I have a GR-DVL140E that trashes the tape when doing backward picture
search. It runs OK in normal forward playback. I have had the drive
disassebled almost completely and re-assembled to fix a problem with the
back tension arm. I can feel that when it runs in backward search mode, it
does not break the right tape wheel, so the tape is completely untight. If I
press it lightly against the tape guide arm to the right of the pinch
roller, it runs OK. And when I remove the pressure, the tape flaps over the
top of the arm and crashes because there is no backtension.

There is only one break at the takeup (right) tape wheel, and this is
disengaged when it runs backward. It seems it would work it this break was
engaged to provide backtension, but I don't know if this meant to be so. It
is a quite strong break, normally used to stop the tape after rewinding, I
think.

 

[Ulrik Smed]

Hi

I have a GR-DVL140E that trashes the tape when doing backward picture
search. It runs OK in normal forward playback. I have had the drive
disassebled almost completely and re-assembled to fix a problem with
the back tension arm. I can feel that when it runs in backward search
mode, it does not break the right tape wheel, so the tape is
completely untight. If I press it lightly against the tape guide arm
to the right of the pinch roller, it runs OK. And when I remove the
pressure, the tape flaps over the top of the arm and crashes because
there is no backtension.
There is only one break at the takeup (right) tape wheel, and this is
disengaged when it runs backward. It seems it would work it this
break was engaged to provide backtension, but I don't know if this
meant to be so. It is a quite strong break, normally used to stop the
tape after rewinding, I think.

No MiniDV experts out there?

I'm really puzzled now, I just tried to fool the drive to think a tape was
inserted by covering the tape end sensors with my fingers while closing the
tape compartment. It spins the drum, loads the (not present) tape and makes
its initial short reverse running as if there was a tape inserted. But now
the break on the right tape wheel IS activated... :-S If it would just do
that with a tape inserted too, I'm sure it would work. Trying back and forth
with tape and no tape gives the same result every time, when a tape is
present the break is deactiveted and the tape trashes.

How can it tell the difference between a real tape and me cheating the tape
end sensors? Of course only one of the tape wheels rotate when there is no
tape (this stops the drive with a warning on the monitor after a short
while), but the break is activated even before the capstan moves.

 

[Ulrik Smed]

I'm really puzzled now, I just tried to fool the drive to think a
tape was inserted by covering the tape end sensors with my fingers
while closing the tape compartment. It spins the drum, loads the (not
present) tape and makes its initial short reverse running as if there
was a tape inserted. But now the break on the right tape wheel IS
activated... :-S If it would just do that with a tape inserted too,
I'm sure it would work. Trying back and forth with tape and no tape
gives the same result every time, when a tape is present the break is
deactiveted and the tape trashes.
How can it tell the difference between a real tape and me cheating
the tape end sensors? Of course only one of the tape wheels rotate
when there is no tape (this stops the drive with a warning on the
monitor after a short while), but the break is activated even before
the capstan moves.

Heh, replying to my own post once again.

I found the problem! There is a pin that sticks up and releases the breaks
inside the tape cassette when it loads. This is controlled by the same plate
that controls the right wheel break. When the pin was loaded by the spring
inside the cassette, it made the plate hang in a slightly wrong position and
thereby did not activate the right wheel break. This is why it all worked OK
without tape.

I fixed it by milling about a half millimeter off the little pin that moves
the wheel break away from the wheel, so the break came closer to the wheel.
This was enough to ensure the break was activated, even with the controlling
plate in the wrong position. It still deactivates OK, the clearance is just
a bit smaller than before, no problem here. So now it runs the tape nice and
tight backwards.