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8950 to 6lb6 conversion
- Thread starter nitroturbo4u
- Start date
The pinout is the same on these tubes other than the 8950 has two pins tied to the cathode terminal. The main difference is the filament voltage is only 6 volts for the 6LB6 tube and 12 volts for the 8950. If you plug a 6LB6 into an 8950 socket you'll burn the filament up. They run a pair in the driver stage because the filaments are in series with each other. Having 5 tubes in the final eliminates that option being an odd number. You might wire the finals so that two pairs of tubes have their filaments wired in series and leave the 5th socket empty or consider a 6 volt filament transformer.
If it were me, I'd avoid purchasing the high demand sweep tubes that have a 6 volt filament and buy something more economical with an obscure filament voltage that you can use to your advantage in this application. Something like the 23JS6C tube. Still under $30 each for NOS. Same 30 watt plate dissipation as the 6LB6 with the same socket and pinout. It just has a 23 volt filament. Isolate all filament pins from the circuit and wire all 5 final tubes in series. Then just drop the string across the AC line after the power switch.
The filaments will light right off the AC line and remove the 6 amp load from the existing power transformer. Allowing it to run cooler and at a reasonable parts cost.
If it were me, I'd avoid purchasing the high demand sweep tubes that have a 6 volt filament and buy something more economical with an obscure filament voltage that you can use to your advantage in this application. Something like the 23JS6C tube. Still under $30 each for NOS. Same 30 watt plate dissipation as the 6LB6 with the same socket and pinout. It just has a 23 volt filament. Isolate all filament pins from the circuit and wire all 5 final tubes in series. Then just drop the string across the AC line after the power switch.
The filaments will light right off the AC line and remove the 6 amp load from the existing power transformer. Allowing it to run cooler and at a reasonable parts cost.
