ULTRA ET4019 tube

[henrypal]

For this radio, which replacement can be used for the TH41 valve. Thank you very much for the information.

[Murphyv310]

Hi
From what I can gather there is no direct equivalent. It is a Mazda octal based valve with a 4 Volt heater. They will be available on eBay and I'm sure someone here may be able to help you with a replacement.

[ppppenguin]

Here's information about it: http://www.r-type.org/exhib/aaq0200.htm

Not my specialist field but I wonder if a common ECH81 could be fitted with an adaptor. Would also need a 6.3V heater supply.

Other triode-heptodes listed here: http://www.r-type.org/inx/inx00405.htm

[henrypal]

Ok Mr. ppppenguin. Thanks

[Mike Watterson]

Any replacement will likely need an International Octal or more likely an old British 7 pin base for 4V as they changed over to 6.3V or 200mA for IO base.
A triode-hexode, triode-pentode, heptode or octode are all fairly interchangeable for MW & LW and lower SW bands. Higher band may need alignment. The triode grid and anode connections go usually to g1 and g2 of a heptode or octode, just look at the circuit of any set using triode-pentode, heptode or octode to see which two pins are the LO input (feedback) and output (usually inductor load) and which pin is RF in. There will be at least one screen grid and maybe a suppressor grid (HT and 0V). I've tested Triode-Hexodes in Octode circuits and even a triodized pentode as the oscillator and a separate pentode with LO feeding g2 and Rf to g1 as mixer. That replaces a triode-hexode, triode-pentode, heptode or octode.

This should work: 41MPG = CV2505 = A80A as long as the base is changed. No need to change any components.

[henrypal]

Now I have more alternative. Thank you.