6240G Data Sheet

[Positron]

I was wondering if anyone has a data sheet for a 6240G vacuum tube? A Japanese manufactured tube used in Luxman Amps back
in the day.

If no one has a spec sheet, I am looking for whatever information I can obtain. Absolute maximum plate voltage, maximum working voltage,
typical plate voltage used in the Luxman 3045 amp, Mu, Gm, Plate Curves etc?

Cheers

Pos

 

[astouffer]

Bottom of the last page. https://www.museum.uec.ac.jp/archive/tube/(010L) Rating of Japanese Receiving Tubes.pdf

Google is literally worthless anymore until you start wrapping quotes around terms.

 

[tubelectron]

I was wondering if anyone has a data sheet for a 6240G vacuum tube? A Japanese manufactured tube used in Luxman Amps back
in the day.

If no one has a spec sheet, I am looking for whatever information I can obtain. Absolute maximum plate voltage, maximum working voltage,
typical plate voltage used in the Luxman 3045 amp, Mu, Gm, Plate Curves etc?

Cheers

Pos

I wonder if it is not a similar tube to the 12BH7, or maybe 6FQ7/6CG7 ?

T

 

[wrenchone]

I just did some searching around, and it looks like a 6CG7 is a suggested replacement.

 

[rayma]

I wonder if it is not a similar tube to the 12BH7, or maybe 6FQ7/6CG7 ?

Kinda, but some of the voltage ratings are different.

 

[wrenchone]

In the searching around, I also found an Ebay seller asking a fairly hideous price for a used pair of 6240Gs, with no guarantee that they actually worked. This, folks, is why I design and build my own amps, with stuff that I know that I can get.

 

[astouffer]

Well in all fairness they were only made for the Japanese market and probably cheap at the time.

 

[wrenchone]

The price was up in the stratosphere, Like Bangy-Bang tubes charges for proletarian plunkers.

 

[bondini]

I just did some searching around, and it looks like a 6CG7 is a suggested replacement.

Not sure of the 6240G pin-out (base=m9-03??) but a substitute looks do-able with some juggling:

• If the gain is important and the the 6240G is handling input under 2VRMS, then I'd be tempted to try the 5670 at maybe Vak=200V, ia=7mA, Vgk=-4V
• If the 6240G is handling big input signals >2VRMS, then the 6CG7 has lower gain but offers at least as much headroom at maybe Vak=200V, ia=9mA and Vgk=-6V

6240G	mu=35	gm=3.5mS	Vak=200V	Vgk=-5V	ia=7mA	heater=600mA	base=m9-03 (??)
6CG7	mu=20	gm=2.6mS	Vak=250V	Vgk=-8V	ia=9mA	heater=600mA	base=9AJ
5670	mu=35	gm=5.5mS	Vak=150V	Vgk=-2V	ia=8mA	heater=350mA	base=8CJ

 

[Sorento]

curves: https://www.mweblabo.com/jf1vrr-2010100600

Japanese datasheet attached ...

 

[Pyka]

 

[bondini]

Same pin-out as the 6CG7, so could try plug-n-play to see how it works

However, the electrical characteristics are more like a high rp version of the 5670 than a high mu version of the 6CG7 ....

 

[Positron]

Thank you gentlemen for your time and efforts. Much appreciated.

I saw the ad for 2 tubes and the price. So much for NOS tubes these days.

Cheers and thanks again.

pos