February 12, 2022 at 10:28 am #18165
Grant, these two tubes cannot go in the same radio. Your second tube has to be a UCH11. The ECH11 has a 6,3V/200ma filament for parallel wired filaments. The UCH11 has a 20V/100ma filament that is wired in series with the UEL11 48V/100ma filament. If the radio is a Telefunken, the only model I found with these two tubes is the SK50. The schematic is available on Radiomuseum.