Emerson 8CW-334 - UK Vintage Radio Repair and Restoration Discussion Forum

newlite4 · 7th Mar 2005, 12:53 pm

I have nearly finished the restoration of this 1940 'All American Five'. It has a typical valve line-up for the year using octal valves. The set was a wreck and had been plundered for spare parts. All of the cut wires have been replaced and many new parts have been fitted. On an initial test, the 12SQ7 (triode detector) was found to have an open circuit heater. I fitted a 6SQ7 as a temporary replacement just to keep the heater chain up together. The original valve had a 12V/0.15A heater, the replacement had a 6V/0.3A heater so I was not expecting the set to function properly. On power-up, sure enough, the voltage across the 6SQ7 heater was sitting at 1V. Sooo, ...imagine my suprise when the set warmed up and reasonable sound quality was heard from the speaker. All this without a functioning triode detector? I cannot explain this, maybe the heater was just warm enough to allow moderate emission? Anyone know why this set is working?
Neil

7th Mar 2005, 12:53 pm	#1
newlite4 Octode Join Date: Nov 2003 Location: Bath, Somerset, UK. Posts: 1,805	Emerson 8CW-334 I have nearly finished the restoration of this 1940 'All American Five'. It has a typical valve line-up for the year using octal valves. The set was a wreck and had been plundered for spare parts. All of the cut wires have been replaced and many new parts have been fitted. On an initial test, the 12SQ7 (triode detector) was found to have an open circuit heater. I fitted a 6SQ7 as a temporary replacement just to keep the heater chain up together. The original valve had a 12V/0.15A heater, the replacement had a 6V/0.3A heater so I was not expecting the set to function properly. On power-up, sure enough, the voltage across the 6SQ7 heater was sitting at 1V. Sooo, ...imagine my suprise when the set warmed up and reasonable sound quality was heard from the speaker. All this without a functioning triode detector? I cannot explain this, maybe the heater was just warm enough to allow moderate emission? Anyone know why this set is working? Neil