Studer A80 supply motor won't spin

[Jordan_A]

The supply motor stopped in a session.
I started to go through it. I've determined that:
-the power transistors for the motor are fine,
-the motor itself is okay (when I swap the connections it spins),
-all the fuses are okay,
-The motor capacitors are okay,
-The cards are all okay (there is another A80 next to it. I swapped all cards and issue does not follow cards)

On my readings for the take up reel, the power transistors are around 190vdc, then when play is pressed, they switch to around 5vdc. The supply reads 190vdc but doesn't switch.

Anyone have any suggestions. I'm starting to run out of ideas.

 

[pvision]

What happens to the power supply voltages on the good machine when it's put into play?

Assuming the motor, cards and power supply on the "bad" machine are OK then the fault must lie in a sensor or control system. What determines the speed of the supply spool? I assume it's controlled by the first set of idlers on the rotating plinth to give the required back tension to the tape path.  Right now, is the supply reel powered in rewind or fast forward? Or is it just a fault in play?

Nick Froome

 

[radardoug]

Brake stuck on?

 

[tubestation]

Hello,
Maybee it s a good Idea to become Member of the Studer List . It s nessesery to subcribe ,can be done here:
http://www.recordist.com/studer/subscribe.html
I don t know about Studermaschienes, but I had a lot of Help with my Ampex MM1100 at the relevant Ampex List.
I would doublecheck the Powertransistors and optos,Drivertransistors in Your Motordriveamp.
Greetings and good Luck
Lothar

 

[Jordan_A]

It was the tape tension sensor. I got the supply reel to spin, however now it is going in the opposite direction. Any ideas?