03-06-2024, 08:40 PM
So at 121.5V, the new 26W lamp is a 9.2W load approximately.
If it was a linear resistance then it would be only about 6.5W at 120V, because power is V squared.
Thus if HT was 243V, the FET would also have 9.2W to dissipate when there is no load.
An EL84 is about 50mA anode max and 6mA screen max.
At 50 mA load (FET and external load added) the voltage drop on the lamp would be about 45V.
The 6 ma screen would be via a a separate lamp with a separate parallel FET. Almost full HT would be available when FET off
Also the FETs sink slightly less as they heat up. No thermal runaway.
The unreadable current on the new 26W lamp was 56.8mA at 60V.
The FETs might be about €2 each.
.
If it was a linear resistance then it would be only about 6.5W at 120V, because power is V squared.
Thus if HT was 243V, the FET would also have 9.2W to dissipate when there is no load.
An EL84 is about 50mA anode max and 6mA screen max.
At 50 mA load (FET and external load added) the voltage drop on the lamp would be about 45V.
The 6 ma screen would be via a a separate lamp with a separate parallel FET. Almost full HT would be available when FET off
Also the FETs sink slightly less as they heat up. No thermal runaway.
The unreadable current on the new 26W lamp was 56.8mA at 60V.
The FETs might be about €2 each.
.
