> Indeed, T&H works correctly but S&H doesn't. Initially I had both
> units in S&H mode.

I have checked the A-164-1/A-148 combo with A-148 in S&H mode. You are
right: this combo does not work. The reason is the AC coupling of the A-148
input in S&H mode in combination with the way how the gate signal is
generated by the A-164-1 (connection to +12V via protection resistor). If
the A-164-1 is not operated the output is open and the coupling capacitor of
the A-148 does not discharge. The T&H does work as in this case the input of
the A-148 is DC coupled.

I found a simple solution: solder a pull down resistor (about 100k) between
GND and the A-148 input. The resistor can be soldered directly to the
corresponding terminals of the socket on the bottom side of the A-148 pcb.
The 100k resistor connects the A-148 input to GND when the button of the
A-164-1 is not operated. Then the AC coupling capacitor of the A-148 is
discharged as necessary. I have tried successfully an 100k resistor but I'm
sure that any other value in the range 47k ... 220k should do the job.

Best wishes
Dieter Doepfer