  We investigate small-scale light variations in V646 Pup occurring on
different timescales with the aim to investigate whether this variability is
similar to that observed in FU Ori. We observed V646 Pup at the SAAO and CTIO
between 2013 and 2018 with Johnson and Sloan filters, typically using a one-day
cadence maintained for 1-4 weeks. We also utilised the public-domain
1512-day-long ASAS-SN light curve and TESS photometry obtained in 2019 over
24.1 days with a 30 min cadence. New SAAO low-resolution spectra assist in
updating major disc parameters, while the archival high-resolution Keck spectra
are used to search for temporal changes in the disc rotational profiles. The
ground-based observations confirm the constantly decreasing brightness of V646
Pup at the rate of 0.018 mag/yr. Precise TESS data show that the slight,
0.005-0.01 mag, light variations imposed on this general trend do consist of a
few independent wave trains of an apparently time-coherent nature. Assuming
that this is typical situation, based on an analysis of colour-magnitude
diagrams obtained for earlier epochs, we were able to make a preliminarily
inference that the bulk of the light changes observed could be due to the
rotation of disc photosphere inhomogeneities, arising between 10-12 solar radii
from the star. We do not exclude the possibility that these inhomogeneities
could also manifest themselves in the rotational profiles of the disc, as
obtained from the high-resolution spectra. Assuming Keplerian rotation of these
inhomogeneities, we give a preliminary determination of the stellar mass at
0.7-0.9 solar mass. These preliminary results are similar to those better
established for FU Ori, which suggests a common driving mechanism(s).
