The picture has reduced in size and has become
square shaped. This condition leaves a black
border around the picture. When the brilliance control is advanced, the picture enlarges and goes out of focus.-A. J. Astell (Bristol, 3).
Check the h.t. voltage output of the LW15 metal rectifier. If this is under 190V, change it. If it is
190V or more, check the PL81 valve inside the
screened section and the ECC82 above it.