Re: Philips 2514
My valves are or should I say would be on 4V AC, The 4V heater wiring has 2 120 Ohm resistor one from each side and they go to the "Chassis" so it is like a centre tap. As I said the B442 equivalent that the radio originally had was directly heated.
OK now I have added the other LND150 in place of the B442. After a few tries I found that a 470R resistor in the source to chassis gave the best results without a decoupling capacitor as the gain was too high and caused instability. Volume control works better too. Ids is around the 2.5/3 mA mark like the valve.
The radio now works although the regen is a bit violent, sensitivity is good but I think I need to play with the decoupling on the Regen Mosfet to calm it down a bit. Instability here is also a function of the long wiring etc I reckon. Only other problem is to reduce the hum, this is not from the HT or -Ve smoothing, increasing the Cs makes little difference, I think it is due to the switching of the 1N4007s so I need to look for some 10nF 1kv caps.
I will tidy up the Mosfet mountings etc with small bits of veroboard.
Anyway these are the pics of how it is now.
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