05-27-2014, 12:13 PM
Personally I wouldn't bother doing that with a tube as readily available as an 80. You can get a new 80 for $12 or good used for $6:
https://docs.google.com/spreadsheet/ccc?...0foD#gid=4
It won't be a globe but it won't require kludging in diodes and resistors under the chassis either. Keep your eyes open and you'll eventually find a good globe 80 on eBay, a radio meet, an old parts set, or a wanted ad. There is no shortage of globe 80's out there if you're patient.
I'd also measure B+ with a good 80 and then your weak one; often a weak 80 isn't that far off, depending on the parameters of the tube tester used.
If you're still determined you can use two 1N4007's and a wire wound resistor to drop the B+ down to what it measures with a known good 80 in the circuit.
https://docs.google.com/spreadsheet/ccc?...0foD#gid=4
It won't be a globe but it won't require kludging in diodes and resistors under the chassis either. Keep your eyes open and you'll eventually find a good globe 80 on eBay, a radio meet, an old parts set, or a wanted ad. There is no shortage of globe 80's out there if you're patient.
I'd also measure B+ with a good 80 and then your weak one; often a weak 80 isn't that far off, depending on the parameters of the tube tester used.
If you're still determined you can use two 1N4007's and a wire wound resistor to drop the B+ down to what it measures with a known good 80 in the circuit.
John KK4ZLF
Lexington, KY
"illegitimis non carborundum"
