07-07-2020, 09:18 PM
(This post was last modified: 07-07-2020, 09:19 PM by Mike Watterson.)
No modification at all needed to the actual radio to replace all the battery valves. Should be no issue on any parallel filament set.
Also the 1j29b with filaments in series can replace 2V valves and run off the 1.8V to 2V lead acid. I have a pair inside the envelope of a KLL32 that arrived cracked at the base. The two homemade screens give it a similar internal appearance. I had to add two resistors as a divider from external g2 to internal g2 and f- for stability and also so the g1 was at the same bias point. But this was inside the package. The g2 and g3 of the two valves tied.
McMichael 484, a 1948 2V lead Acid set. Basically old pre-war "British base" valves simply given octal bases in 1945/1946. A fifth of homes had no electricity in the UK in 1948 and a Lead-Acid Table model was much cheaper to run than an "All Dry" set.
Since the 1j24b will work down to 0.9V or possibly less, the circuit above might replace a KK32, with possibility it might work with the two filaments in series. I have tried a DK92 in a KK32 socket, with a resistor on f+ to drop the 2V to 1.3V, that worked perfectly.
Schematic
As received
(cracked at base)
Old insides
New insides
And envelope glued on!
Home made B7G plugs
Also the 1j29b with filaments in series can replace 2V valves and run off the 1.8V to 2V lead acid. I have a pair inside the envelope of a KLL32 that arrived cracked at the base. The two homemade screens give it a similar internal appearance. I had to add two resistors as a divider from external g2 to internal g2 and f- for stability and also so the g1 was at the same bias point. But this was inside the package. The g2 and g3 of the two valves tied.
McMichael 484, a 1948 2V lead Acid set. Basically old pre-war "British base" valves simply given octal bases in 1945/1946. A fifth of homes had no electricity in the UK in 1948 and a Lead-Acid Table model was much cheaper to run than an "All Dry" set.
Since the 1j24b will work down to 0.9V or possibly less, the circuit above might replace a KK32, with possibility it might work with the two filaments in series. I have tried a DK92 in a KK32 socket, with a resistor on f+ to drop the 2V to 1.3V, that worked perfectly.
Schematic
As received
(cracked at base)
Old insides
New insides
And envelope glued on!
Home made B7G plugs
