23-09-2019, 08:22 PM
Hello all.
Seems like the discussion has turned to the shortcomings of the ecl80 valves.
The reason that I used one is:
The Grundig set used another (albeit larger) common cathode type, and I wanted to make a comparison.
I have ten NIB.
Its a small valve, and I don't need a ghetto blaster.
Heater consumption is modest and 6.3Volt.
I was confused about the talk of 3volts bias, and where that came from? then I realised that I put that on the diagram! It was a vestige from the Grundig literature.
What I actually did was provide the bias from the GB output of dads old bench supply that will give a referenced adjustable, low current negative supply. I just lazily adjusted it for anode current, and accepted it.
As eagle eyes Lawrence spotted it, I switched on the project just now, and noted the value of bias.
It's -6.7volts.
Well done.
Oh, and I don't much like this biasing set up either, I don't think it would be long term stable. At least in the Grundig set it would self adjust to a degree virtue of the current through the 70 ohm resistor, but its just experimental.....
Thanks,
Amie.
Seems like the discussion has turned to the shortcomings of the ecl80 valves.
The reason that I used one is:
The Grundig set used another (albeit larger) common cathode type, and I wanted to make a comparison.
I have ten NIB.
Its a small valve, and I don't need a ghetto blaster.
Heater consumption is modest and 6.3Volt.
pwdrive Wrote:Thomas Cook
I was confused about the talk of 3volts bias, and where that came from? then I realised that I put that on the diagram! It was a vestige from the Grundig literature.
What I actually did was provide the bias from the GB output of dads old bench supply that will give a referenced adjustable, low current negative supply. I just lazily adjusted it for anode current, and accepted it.
As eagle eyes Lawrence spotted it, I switched on the project just now, and noted the value of bias.
It's -6.7volts.
Well done.
Oh, and I don't much like this biasing set up either, I don't think it would be long term stable. At least in the Grundig set it would self adjust to a degree virtue of the current through the 70 ohm resistor, but its just experimental.....
Thanks,
Amie.
