  We present experimental results of a homopolar disc dynamo constructed at
CICATA-Quer\'etaro in Mexico. The device consists of a flat, multi-arm spiral
coil which is placed above a fast-spinning metal disc and connected to the
latter by sliding liquid-metal electrical contacts. Theoretically,
self-excitation of the magnetic field is expected at the critical magnetic
Reynolds number Rm~45, which corresponds to a critical rotation rate of about
10 Hz. We measured the magnetic field above the disc and the voltage drop on
the coil for the rotation rate up to 14 Hz, at which the liquid metal started
to leak from the outer sliding contact. Instead of the steady magnetic field
predicted by the theory we detected a strongly fluctuating magnetic field with
a strength comparable to that of Earth's magnetic field which was accompanied
by similar voltage fluctuations in the coil. These fluctuations seem to be
caused by the intermittent electrical contact through the liquid metal. The
experimental results suggest that the dynamo with the actual electrical
resistance of liquid metal contacts could be excited at the rotation rate of
around 21 Hz provided that the leakage of liquid metal is prevented.
