OT: american vs european 220

That sounds right, but I would have to get the data books out to check. US valve numbers have absolutley no logic to them... I don;t think there was a UK version of this valve. We had a range of vavles with 100mA heters, but te rectifier (UY85) and output pentode (UL84) had heterrs around 40-50V. There was a 50mA range of valves (VY2, VCL2, ertc) but they were only used on the continent. Cheap record playes over here tended to use the turntable motor widing and an autotransformre to run the valve heaters (series string totalling around 100V) and get the HT (B+) by half-0wave rectifying the mains. Right... We had DC mains in England into the 1950s in some areas. A lot of radios and TVs weew 'AC/DC',not just to save the cost of the mains transformer. I rememebr working on TVs (long after the 1950s, of coruse) with different voltage selector settings for AC and DC mains (possibly due to fact that the smoothing capacitor would charge to the peak and not the RMS votlage of AC mains). One of the Mullard books of audio amplfiier cirucits (including things like the 5-10 and 5-20) includes a circuit for an amplifier (4 valves, something like UF86, 2 * UCL82, UY85) for AC/DC mains. Of coruse it was hot-chassis which is a right pain... DC mains was somethign of a pain too. It was not smooth DC. It came from commutator-type generators and had a lot of relatively high frequency (audo band) ripple/noise on it. Non-triival to keep out of audio amplifiers! Even if the mains was AC, it wasn't necessarily 50Hz. I think all sorts of other frequencies were used in some areas at some times. Certainly Lynmouth (north Bevon) had 100Hz mains until the hydro-electric power station was destroed in the floods of 1952. -tony