WOULD ANYONE HAVE SOME EXPERIENCE WORKING ON AN OLD TASCAM 85-16 1"
16 TRACK?
I BOUGHT ONE IN PRETTY GOOD SHAPE EXCEPT THE CAPSTAN MOTOR RUNS ABOUT
70 IPS.
THE PITCH CONTROL SWITCH DOES NOT WORK. I HAVE THE SCHEMATICS WITH THE
DECK AND
HAVE BEEN LOOKING AT THE CAPSTAN SERVO BOARD. MIGHT ANYONE HAVE A CLUE
WHERE TO LOOK? THANKS GLENN.

In article writes:

I BOUGHT ONE IN PRETTY GOOD SHAPE EXCEPT THE CAPSTAN MOTOR RUNS ABOUT
70 IPS.
THE PITCH CONTROL SWITCH DOES NOT WORK. I HAVE THE SCHEMATICS WITH THE
DECK AND
HAVE BEEN LOOKING AT THE CAPSTAN SERVO BOARD. MIGHT ANYONE HAVE A CLUE
WHERE TO LOOK?

Right where you're looking. But servo systems are difficult to
troubleshoot because there's an input that's related to the output.
I'd look at the speed sensor and then the path from there to whatever
controls the motor current. Apparently the stage that regulates the
motor voltage doesn't know that the motor has reached the correct
speed, so it continues to try to speed it up.



--
I'm really Mike Rivers - )

Glenn Taylor wrote:
WOULD ANYONE HAVE SOME EXPERIENCE WORKING ON AN OLD TASCAM 85-16 1"
16 TRACK?
I BOUGHT ONE IN PRETTY GOOD SHAPE EXCEPT THE CAPSTAN MOTOR RUNS ABOUT
70 IPS.
THE PITCH CONTROL SWITCH DOES NOT WORK. I HAVE THE SCHEMATICS WITH THE
DECK AND
HAVE BEEN LOOKING AT THE CAPSTAN SERVO BOARD. MIGHT ANYONE HAVE A CLUE
WHERE TO LOOK? THANKS GLENN.

Put it on an extender. Get out the scope and start tracing around...
look first at the signal from the motor tach, then trace it through the
tach electronics and then the phase detector.

Check the reference oscillator too, although that is much less likely
to have problems. If the phase detector has both good reference and
good tach going into it, see what is coming out.

Then go through to the amplifier stage and see if that is jammed to full
speed. Start at the beginning and work through to the end.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

I still have an 85-16 1". My tape counter does not work, and also the pitch
control, because I took it apart looking for a slight scraping noise, and I
accidentally bent the photo sensor wheel (the one with all the holes punched
along the circumference). I ended up having to remove it completely. Be
careful in there! It really sucks scratching pencil on tape reels to mark
beginnings of songs. Not a lot of 8616 techs running around these days, at
least near Dallas, that I am aware of.

Almost sounds like the capstan is not engaging at all (?), you might look at
that pitch control circuit - as if its up all the , although I do not know
that 70 IPS was possible even with the pitch wheel.

You are running almost at double speed - that could be a clue. Missing 1/2
the feedback signals somewhere...




"Glenn Taylor" wrote in message
m...
WOULD ANYONE HAVE SOME EXPERIENCE WORKING ON AN OLD TASCAM 85-16 1"
16 TRACK?
I BOUGHT ONE IN PRETTY GOOD SHAPE EXCEPT THE CAPSTAN MOTOR RUNS ABOUT
70 IPS.
THE PITCH CONTROL SWITCH DOES NOT WORK. I HAVE THE SCHEMATICS WITH THE
DECK AND
HAVE BEEN LOOKING AT THE CAPSTAN SERVO BOARD. MIGHT ANYONE HAVE A CLUE
WHERE TO LOOK? THANKS GLENN.