We present spectroscopy of three hydrogen-deficient central stars of faint planetary nebulae, with effective temperatures (Teff) in excess of 100000K. The nucleus of RaMul 2 is a Population II Wolf-Rayet star of spectral type [WC], and the central stars of Abell 25 and StDr 138 are two new members of the PG1159 class. Our spectral analyses reveal that their atmospheres have a similar chemical composition. They are dominated by helium and carbon, which was probably caused by a late helium-shell flash. Coincidentally, the three stars have similar masses of about M=0.53M_{sun} and, hence, form a post-AGB evolutionary sequence of an initially early-K type main-sequence star with M=0.8M{sun}. The central stars cover the period during which the luminosity fades from about 3000 to 250L{sun} and the radius shrinks from about 0.15 to 0.03R{sun}. The concurrent increase of the surface gravity during this interval from logg=5.8 to 7.2 causes the shutdown of the stellar wind from an initial mass-loss rate of log(dM/dt)/(M{sun}_/yr)=-6.4, as measured for the [WC] star. Along the contraction phase, we observe an increase of Teff from 112000K, marked by the [WC] star, to the maximum value of 140000K and a subsequent cooling to 130000K, marked by the two PG1159 stars.
