Well I have nothing to loose by trying to get hold of a bag of ferrite beads.
At present I have only the 9 pin valve socket connected, added an aluminium plate as a shield between the adaptor socket and the valve holders.
I have tried co-ax cable on the banana leads grounding with trying to ground the outer sheath. The only time I managed to stop it from oscillating was when I tightly gripped the length of the leads together in my hand!
I have 1nF caps from each banana socket to chassis, 1nF and 10uF across the g2 connection to chassis, 22uF across the HT and even decoupled the heater wires.
The bias is basically now just two PP3 batteries in series to give -18 Volts across a 5K multi-turn linear pot with the +ve connected to the cathode connection which is connected to chassis. The wiper has co-ax to the grid connector with 1nF and 10uF cap to chassis.
I seem to be able to make it worse by adding caps across the vale socket to ground?
Other then that HT comes in 22uF Cap. To the g2 connector and across a volt meter with range switch, also to a mA meter again with range switch to the anode connection, I must do a circuit for myself so I can keep track of things.
The buzz of the rf bug detector is getting really annoying.
Thanks all for your comments.
Adrian