Wavetek 2001 no 16V signal

[RAPo]

I got a Wavetektek 2001 sweeper.
The MH2 module (=sweepdrive) should be generating a 16V signal, but only gives -4.05V.
I've measured some critical pins. The green ones (see image) are oke and at pin 10 there is a 32Vpp ramp signal.
This module is very tightly screwed to the chassis. Before I try to open it, I have 2 questions:


Question 1: Any idea about the source of the error? Moving the pot R95 only marginally changes the signal value.
Question 2: in the module is a component TD101, a six-legged NPN-NPN matched transistor pair. Any idea how to test this component?

Thanks in advance for the help.