On Dec 5, 7:47 am, EADGBE wrote:
On Dec 5, 7:15 am, "Mark D. Zacharias"
wrote:



Does the Timer Play function work normally?

Mark Z.

Mark:

I tried it.

No, the deck cannot enter PLAY mode under
any circumstances.

1) was it able to enter play before the bias osc was repaired?
2) is the timer switch in record mode?
3) I think the voltage you are reading at the wiper is the voltage
from the pot and indicates what position the cam is in. You need also
to read the volatge that the machine is commaning the motor to go to
so sometinh is amiss with the circuit around Q430 in fig 2.3.22

4) see fig 2.3.22 what is the voltage at Q430 collector in play and
pause. This is an interesting circuit, it looks like the macinh
gnerates a voltage for each mode and then the motor moves the cam
until it is in the correct position to null the voltage at the op
amp...so you have determined that the cam is not moving correctly by
reading the pot voltage, but you need to determine is the voiltage
wrong becasue the circuit is getting the wrong commmand or maybe it is
physically stuck and unable to move to the correct position.

5) The votage on the op amp IC405 input pins 6 and 5 should be
"virtually" equal. If they are not equal, then the there should be a
voltage on the motor and it should be trying to turn.
If they are equal, then the mechinsim is doing what it is told and it
is being told to do the wrong thing and the problem is in the command
voltage inputs.

6) It looks like the only differnce in the comman between play and
pasue is due to the different values of R511 and R514. Make sure the
logic signal to them is correct. These different values shoulsd
create a differnet input to the op amp and the motor should move and
move the cam pot so the voltage on pin 6 and 5 is equal again. This
is a big mechanical feedback loop that tries to keep the voltage on
pin 6 and 5 equal.

Very nice manual by the way...thanks good luck , let us know what you
find.

Mark