Noise figure meter Magnetic AB 117a / schematic

[loulou31]

Hi

I have bought a old noise figure meter  model 117A from Magnetic AB. Magnetic AB IS a company based in Sweeden and was designing specific instruments.
This instruments is in trouble and started to repair it without any schematic or synoptic. I have found the problem on the AGC signal  processiing. When I force the AGC voltage between 0 to 4V to the RF module there is dôme amplification and signal détection. Without any signal or with signal the AGC is always -5v and there is no any gain.
I started  to draw the diagram of the board in charge of AGC but seems not obvious to understand.
If I could have schematic or principle of opération of instrument that will help.

Regards

Jean-Louis