GELÖST - STUDER B67 MkI : kein Aufnahme
Verfasst: Dienstag 5. Juli 2016, 14:43
Hello there,
Sorry for writing in english but I don't really master Deutsch.
A friend asked me to overhaul his Studer B67, which I did : all electrolytic and tantalum capacitors have been replaced on all of the audio boards, stabilizer and oscillator boards.
On the Tape Transport Control Board 1.67.761 I also had to replace one of the spooling motors control ICs (one TCA561 was dead, and it costs a fortune).
After the base revision was completed I started the calibration process as per the Service Manual : demagnetization, playback head azimuth, output levels, frequency response etc. And then I wanted to start the record amplifiers calibration but, and it is a big BUT, the machine doesn't record anything on tape !
Of course I first suspected something wrong in the record amplifiers, so I swapped them with my own B67 record amplifiers, to no avail.
I also checked voltage at pin J3-10 (Y-REC) on board 1.67.761 to find that when RECORD function is engaged by pressing RECORD and PLAY keys together, it drops from 12V to 0V. So I assume that Q12 base conduction is activated by IC1 (SC10429), concluding that it is alive and working. When machine is running in recording mode, tape is normally erased and the oscillator frequency is exactly 150KHz, so there are no issues there. All other functions are working normally.
This B67 has no VU-meters nor control panel. Of course I verified correct jumpers position on interconnection board, and I also visualized with the oscilloscope and 1KHz generator that input sinusoidal waveform arrives intact on the record amplifiers inputs.
Now I'm lost and I don't know where to look for fault, could someone put me on right tracks please ? I am running out of ideas...
Thanks for your help !
Thierry
Sorry for writing in english but I don't really master Deutsch.
A friend asked me to overhaul his Studer B67, which I did : all electrolytic and tantalum capacitors have been replaced on all of the audio boards, stabilizer and oscillator boards.
On the Tape Transport Control Board 1.67.761 I also had to replace one of the spooling motors control ICs (one TCA561 was dead, and it costs a fortune).
After the base revision was completed I started the calibration process as per the Service Manual : demagnetization, playback head azimuth, output levels, frequency response etc. And then I wanted to start the record amplifiers calibration but, and it is a big BUT, the machine doesn't record anything on tape !
Of course I first suspected something wrong in the record amplifiers, so I swapped them with my own B67 record amplifiers, to no avail.
I also checked voltage at pin J3-10 (Y-REC) on board 1.67.761 to find that when RECORD function is engaged by pressing RECORD and PLAY keys together, it drops from 12V to 0V. So I assume that Q12 base conduction is activated by IC1 (SC10429), concluding that it is alive and working. When machine is running in recording mode, tape is normally erased and the oscillator frequency is exactly 150KHz, so there are no issues there. All other functions are working normally.
This B67 has no VU-meters nor control panel. Of course I verified correct jumpers position on interconnection board, and I also visualized with the oscilloscope and 1KHz generator that input sinusoidal waveform arrives intact on the record amplifiers inputs.
Now I'm lost and I don't know where to look for fault, could someone put me on right tracks please ? I am running out of ideas...
Thanks for your help !
Thierry