Hi, I'm currently in the process of restoring an Ampex 351 transport and a couple of Inovonics Model 380 electronics preamps.
I have a problem that I can playback and record, but there is no erase.
The bias voltages seem to be correct as I measured 250kHz at pin 22 of the RECORD PCB (record bias) and 125kHz at pin 3 of the RECORD PCB (erase bias).
I measured the resistance and inductance of the heads and the readings seem to be good.
Left channel:
Erase: 1.32mH /84R
Record: 13.9mH / 19.8R
Repro: 528mH / 259.8R
---------------------------------
Right channel:
Erase: 1.4mh / 90.5R
Record: 13.5mH /19.8R
Repro: 506mH / 261.5R
According to the Ampex manual: "Whenever the PLAY button on the tape transport is depressed, 115 volt d-c is available at pin 3 of 5J7, and when RECORD button 486 is depressed, the 115 volt d-c is applied to the record relay coil. As long as 115 volt d-c is available at pin 3 of 5J7, contact 3K1A holds the relay energized. When the STOP button on the tape transport is depressed, the 115 volt d-c no longer reaches pin 3 of 5J7 and relay 3Kl is de- energized and drops out."
Now I'm trying to understand where the 115DCV comes to pin 3 of 5J7? from the rectifier of the transport circuit or from the preamp PSU?
I have a problem that I can playback and record, but there is no erase.
The bias voltages seem to be correct as I measured 250kHz at pin 22 of the RECORD PCB (record bias) and 125kHz at pin 3 of the RECORD PCB (erase bias).
I measured the resistance and inductance of the heads and the readings seem to be good.
Left channel:
Erase: 1.32mH /84R
Record: 13.9mH / 19.8R
Repro: 528mH / 259.8R
---------------------------------
Right channel:
Erase: 1.4mh / 90.5R
Record: 13.5mH /19.8R
Repro: 506mH / 261.5R
According to the Ampex manual: "Whenever the PLAY button on the tape transport is depressed, 115 volt d-c is available at pin 3 of 5J7, and when RECORD button 486 is depressed, the 115 volt d-c is applied to the record relay coil. As long as 115 volt d-c is available at pin 3 of 5J7, contact 3K1A holds the relay energized. When the STOP button on the tape transport is depressed, the 115 volt d-c no longer reaches pin 3 of 5J7 and relay 3Kl is de- energized and drops out."
Now I'm trying to understand where the 115DCV comes to pin 3 of 5J7? from the rectifier of the transport circuit or from the preamp PSU?
