[dave_n_t]

Tim,

A couple of clarifications, plse, to aid 'distant diagnosis':

are you running from the (internal) mains supply; battery (i.e. replacement battery made from PP3s, etc.); or a (mains powered) battery eliminator? It might be good to eliminate these as possible causes.

You say that HT goes down - do you mean the power supply HT, or the voltage at the top end of the o/p transformer? What about the voltage across the output transformer (this is a reasonable measure of anode current in the DL96, since the winding resistance is likely to be fairly constant)?

And, where are you measuring the HT voltage (many of these sets have a 'self-bias' resistor in the HT -ve lead (around 470 ohms or so - if excessive current is being taken by the set, the voltage across this will rise.

My valve data says the grid voltage shd be about -5V; so with -19V the valve may well be cutting off....

dave