QuadTech 1657 RLC Digibridge Instruction Manual page 41

Also, the amplitudes of the staircases depend on the RANGE selected
and the impedance components of the DUT. The chosen conditions
make 1 staircase taller than the other 7; so the waveform can be
"stopped", by careful setting of scope sweep trigger adjustment.
(Preferably, trigger on the positive slope, at a low voltage. )
h. Check at the comparator output U44 pin 14 or test point S03 pin 2
for CMP, a positive pulse (+5 V) on a
base line about -5 V dc. Otherwise, U44 is faulty.
i. If a nonfunctional instrument passes all the preceding checks, i.e., no
fault can be found in the analog circuitry, the fault is liable to be in digital
circuitry.
See below.
5.8.5 Control Signal Checks.
If there is no staircase waveform at the integrator output (U44 pin 8),
as described above, the following procedure is recommended to determine
whether the fault is in the digital control circuitry.
Figures 5.10, 5-11.
ga. If step g is not verified, check at the switch control terminals
U40 pins 5,6, 12, 13 for the presence of digital
signals with logic high and low levels of +5 V and -8 V.
If all of these signals are present, either U40 or U44 is
faulty; replace both of them. Otherwise, check U33 and U34.
Also refer to para 5.8.5.
SERVICE 5-15