13-01-2020, 09:11 AM
Apply 6.3V from a bench PSU and measure the current. If the current corresponds with the data sheet for the E type, then it's right first time. Otherwise wind up the PSU to the heater voltage for the P type. If the current is 300mA then you know it's a P type. If the current is still low then it must be a U type. To prove this, wind up to the U type heater voltage and check that the current is 100mA.
Doesn't matter if you use DC or AC but DC from a bench PSU is more convenient.
If you suspect it's an odd heater current (C for 200mA, H for 150mA etc) then you need to take more care. Not many in B9A/B7G bases.
Also beware of battery valves. Applying 6.3V to a D type valve will usually blow the filament.
Doesn't matter if you use DC or AC but DC from a bench PSU is more convenient.
If you suspect it's an odd heater current (C for 200mA, H for 150mA etc) then you need to take more care. Not many in B9A/B7G bases.
Also beware of battery valves. Applying 6.3V to a D type valve will usually blow the filament.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
