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Old 23rd Sep 2019, 3:45 am   #51
Synchrodyne
Nonode
 
Join Date: Jan 2009
Location: Papamoa Beach, Bay of Plenty, New Zealand
Posts: 2,943
Default Re: Valve Items - Philips/Mullard Rimlock-to-Noval Transition

The UL41 was probably amongst the last of the main Rimlock series to have a noval successor, namely the UL84 of c.1955. Until then the UL41 would have served as the standard output valve for European radio receivers that used 100 mA series-string valves. The EL84, European noval successor to the EL41, had arrived a few years earlier. The UL84 (and PL84 and EL86) looked to have been more of a design challenge given that they needed to deliver full power at 170 volts on the anode, so that might have been one reason for the apparent delay as compared with the EL84. They required aligned screen grids to help keep screen grid current low and so total cathode current at a sanitary level. Not so much developing the technique, but enabling its reliable production at acceptable costs might have taken extra time. (It might have been more difficult to do it with high-slope pentodes, with their close grid spacings, than with lower slope beam tetrodes, where the technique was well established.)

There was a UL80 that was released quite early on. But the limited available information indicates that this was simply a 100 mA heater version of the EL80/6M5 Innoval (itself a noval version of the EL41), and was thus not configured for 170-volt HT operation. Where it was sold and used I do not know. It does not appear to have had an American registration. In similar vein there were the UCH80 and UF81, noval versions of the ECH80/6AN7 and EF81/6BH5. The UBC81 may also have been an early release, part of this group, but held back in Europe (in favour of the UBC41) until c.1954-55.


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