I realized that the black AA board I mentioned on the last entry has the same range issue as Valera reported before (see #3911).
Basically our ADC card has +/- 10V input range, but on the other hand the AA board is already limited by approximately +/- 2V.
We have to fix it.
The output signal from the VCO box goes to a black beakout board on 1X2 rack though a BNC cable.
Then the signal comes out from the back side of the board with DB39 style, so I put a DB39 to SCSI adapter so that we can take it to the IO chasis.
Now the SCSI is connected to ADC_1 (the second ADC card) on the IO chasis at 1X1.