Studer A807 motor problem

carlosraj

Well-Known Member
Oct 22, 2017
22
0
66
Hi

I am having a problem with my studer. When I press play, the recorder does play, but the take up motor (right hand side) moves slower than the supply motor (left hand side). What happens is that the excess tape from the left reel gets stuck into the reel. It looks like both the motors are not synchronized. This player had a tape tension problem earlier. The "tape tension sensor coil" was replaced a few months back and after that it was playing fine all the while until now. I have also done a complete recapping more than a year ago. What can be the problem.
Today, I realised that the tape tension lever appeared to be loose, so I tightened the spring attached to it. I then readjusted the tape tension ( +4V at minimum tension and 0V at maximum tension) . When I press "play" surprisingly it was playing as normal. I tried playing at all 3 different speeds, fast forward, stop and play, then rewind and play several times and there seem to be no problem. I left it On for some time and then recorded some music at 15ips on 1 full tape. Rewind back and play, all was fine. I then turned OFF the player for a few minutes, turned it ON and play, then it started to play at a very fast speed and the right hand motor was moving slower than the left hand motor and the tape start spilling out. At times, if I turn ON the player, and then press play after a few minutes later, it works normal. I am rather confused on what the problem can be. Can it be the capstan motor, if it is the motor caps problem, then how come it worked as normal, recorded as normal and played back as normal.
This is something very unusual I realised today, Whenever I press "play", the capstan and pinch roller are moving unusually fast. Even when I select different speeds (3.75ips, 7.5ips, 15ips) during play, the capstan and pinch roller speed remains constant(fast). The other thing I noticed is that, when I set to "varispeed", altering the varispeed pot from minimum to maximum does not effect the capstan speed at all. It remains constantly fast. Since the pinch roller is feeding the tape faster to the right hand motor(pulling faster from the left hand motor), it appears that the right hand motor is moving slower than the left hand motor and not able to take up the tape in time, and the tape overflows and gets stuck into the reel. If I am not mistaken, I guess the problem in on the capstan motor board or can it be the command(tape deck electronics board). Please assist.

Thanks
 

carlosraj

Well-Known Member
Oct 22, 2017
22
0
66
Hi

I am having a problem with my studer. When I press play, the recorder does play, but the take up motor (right hand side) moves slower than the supply motor (left hand side). What happens is that the excess tape from the left reel gets stuck into the reel. It looks like both the motors are not synchronized. This player had a tape tension problem earlier. The "tape tension sensor coil" was replaced a few months back and after that it was playing fine all the while until now. I have also done a complete recapping more than a year ago. What can be the problem.
Today, I realised that the tape tension lever appeared to be loose, so I tightened the spring attached to it. I then readjusted the tape tension ( +4V at minimum tension and 0V at maximum tension) . When I press "play" surprisingly it was playing as normal. I tried playing at all 3 different speeds, fast forward, stop and play, then rewind and play several times and there seem to be no problem. I left it On for some time and then recorded some music at 15ips on 1 full tape. Rewind back and play, all was fine. I then turned OFF the player for a few minutes, turned it ON and play, then it started to play at a very fast speed and the right hand motor was moving slower than the left hand motor and the tape start spilling out. At times, if I turn ON the player, and then press play after a few minutes later, it works normal. I am rather confused on what the problem can be. Can it be the capstan motor, if it is the motor caps problem, then how come it worked as normal, recorded as normal and played back as normal.
This is something very unusual I realised today, Whenever I press "play", the capstan and pinch roller are moving unusually fast. Even when I select different speeds (3.75ips, 7.5ips, 15ips) during play, the capstan and pinch roller speed remains constant(fast). The other thing I noticed is that, when I set to "varispeed", altering the varispeed pot from minimum to maximum does not effect the capstan speed at all. It remains constantly fast. Since the pinch roller is feeding the tape faster to the right hand motor(pulling faster from the left hand motor), it appears that the right hand motor is moving slower than the left hand motor and not able to take up the tape in time, and the tape overflows and gets stuck into the reel. If I am not mistaken, I guess the problem in on the capstan motor board or can it be the command(tape deck electronics board). Please assist.

Thanks


Today, I took the readings at Test Pt2(Tacho). There is a 7.5V DC reading. When I switch ON the recorder, my digital multimeter shows a reading of around 75 Hz. When I press play, the reading goes up to around 7.2 to 7.5KHz and more at times. Even though I select different speeds, the frequency remains same. On the scope it shows a sine wave. At Test Pt3(commutation freq), the frequency is also around 7.2 to 7.5KHz and reads approx. 2.4VDC and also does not change with speed select. Something surprising happened when I was taking the frequency readings at Test Pt2 For a brief moment, the recorder started to work normal, the capstan slowed down and was following the speed selction. I let it run at 7.5ips and it was running at this speed correctly for a brief moment and then suddenly it took off to a high speed. The capstan is running so fast that I can hear the whirling sound. I checked a few small transistors, all of them seem to be OK except Q1 (BF366). I took out the transistor and did a diode check with my DMM. It shows a diode drop(0.6V) from base to Emitter but OL from base to collector. If I am not mistaken, Q1 with L1 forms then 5.5MHz oscillator and linked to the capstan Tacho. I need help in tracing what could be the problem. Please assist.

Thanks
 

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