[Heatercathodeshort]

This was a very common fault with the Ferguson 306T. The original models used an unreliable coupling capacitor to the PL81 control grid. This was .001uf but was later modified and all models were fitted with a .01uf component. The anode usually glows a dull red when the fault slowly appears.

STEVE P has probably mentioned this, but I cannot recall the actual circuit numbers.

EY86 failure, after only a short period of use, was very common with early models. The transformer supplied around 7v instead of 6.3v and Mullard produced a special valve for this set known as the TY86F [The 'F' standing for Ferguson] This had a 7.3 volt heater, if I remember correctly. My bet's on the coupling cap.
Regards John.