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jayceebee · 27th Jan 2018, 10:32 pm

According to my 1968 Mullard data book the AW47-91 is a suitable replacement for the 7601A and CME1901, it has a 1" shorter neck and the only circuit change required is the addition of a 21Ω 2W resistor in series with the heater as it's a 6.3V type as opposed to 12.6V for the GEC/Mazda. The heater current for all three types remains the same at 300mA.

The AW47-91 was superseded by the A47-14W, the latter having a tinted faceplate.

John.

27th Jan 2018, 10:32 pm	#2
jayceebee Heptode Join Date: Jun 2007 Location: Durham, County Durham, UK. Posts: 640	Re: GEC BT336 possible tube change According to my 1968 Mullard data book the AW47-91 is a suitable replacement for the 7601A and CME1901, it has a 1" shorter neck and the only circuit change required is the addition of a 21Ω 2W resistor in series with the heater as it's a 6.3V type as opposed to 12.6V for the GEC/Mazda. The heater current for all three types remains the same at 300mA. The AW47-91 was superseded by the A47-14W, the latter having a tinted faceplate. John. Last edited by jayceebee; 27th Jan 2018 at 10:42 pm. Reason: more info