There is a line whistle present. The PY81 /20P4 are OK. There was a blue glow in the 20P4. I
replaced this valve but the glow appears in the new one also. This glow moves up and down
when the line hold is adjusted. To make a neon light, you have to touch the top of the PY81 /20P4.
E.H.T. at the tube connection is almost nil
and when this connection is removed it makes no difference. I cannot tell whether the e.h.t. rectifier is lit. -N. Irvine (Solihull, Warwickshire). If the circuit is working properly, the neon would light when placed in the vicinity of the
transformer. Check the 025µF boost line capa- citor and resistors to pin 4 of the 20P4 base.