A capacitor problem, perhaps. Check the 7Vref to the Dolby ICs. Does the VUs still deflect or will they fall to zero as sound disappears? Martin

Hi Martin. I will check the 7v ref.   But  Dolby is OFF. Yes the VU  follow the sound. If I gently touch the pins on tapehead, L and R, with my screwdriver I get 50 Hz hum i both. Very clear, steady and strong signal.    No dropout in hum.

Sounds like a mechanical problem, - misaligned tapeheads or something bent in the tape path. Is the tape running off the head? Martin

The Recording is OK.  Only one head.   Tape is running perfect on head.   Only Playback problem..

Did you check the 7Vref? It's not important if Dolby is in or out. The signal runs through parts of the Dolby ICs regardless. Martin

No time yet, but will do it soon.  Thanks again for fine info,

Result of checking the 7 volt.     Both L and R were 6,89 Volt and the 14 volt is 13,8 Volt. So I think thats fine.   But again, with 50 hz hum on the tapehead,  I get fine signal in both channels as long as I will. Is it possible to connect a sinus signal from a tonegenerator at the tapehead.  (input on playback amplifier) Or do you have any other suggestions I would be happy  ? Thanks again Martin.  

So... Sound drops out after a few seconds, and VU-meters follow? The tape keeps running? Both tape reels are rotating? And if you touch the tapehead solder tags you get a buzz from the speakers and deflection on the VU-meter? Sure the tape has a good recording on it? Martin

yes to all. I will try to find another tape, and also have another tapedeck (working) and will make a  new recording on that. Will a bad/very old tape have that performance,  sounds OK a short time, then silence.  ?