03-06-2024, 07:33 PM
(This post was last modified: 03-06-2024, 07:40 PM by Mike Watterson.)
It's a less than 20W transformer. I think worst case is no load and about 50% volts? At max volts there is no current. Worst case current at zero volts there is a 26W lamp fed by 240v (less here), about 110 mA max, or if two lamps in parallel, 217mA, but that ignores the power limiting of the shaver transformer's core design, so I doubt more than 150mA is possible. Or less than 75mA on the voltage doubler mode. I'll put an old Pentium II or similar heatsink and see.
An EL34 ought to be tested in ita amp. It's about 90mA anode and 20mA screen. The FET in that situation would be off. Pa 25W The vg for cut off might be -40V
An EL84 is about 50mA anode max and 6mA screen max.
With two lamps in parallel and the nominal 300V supply and output at 150V and no load you might see about be 25W to 30W on the FET, but that's impossible due to the transformer limiting at 20W. I can't imagine more than about 8W to 12W worst case on the FET with no external load. Hard to say without plotting V/I for transformer rectified and R vs I or V for lamps.
Some actual measurements. lamps are rated 230V-240V
Cold (about 19 °C)
15W (small bayonet) 333 Ω
25W (small ES, old) 195 Ω
26W (small ES, new) 169 Ω
Hot @ 121.5V AC (based on measuring AC current)
25W (small ES, old) 1841 Ω
26W (small ES, new) 1599 Ω
Hot @ 235V AC based on wattage
25W (small ES, old) 2209 Ω
26W (small ES, new) 2124 Ω
Approx Current mA
Vs 25W 26W
30 27 44
40 32 48
50 35 53
60 43 --*
121.5 66 76 (Actually an autotransfomer. I only have insulated one screw holder, so didn't test the bayonet model.
[* can't read my note!]
So due to much hotter at rated voltage, the resistance swing is far more than for valve heaters.
The only new filament lamp in the regular shops now is the Philips 26W smaller ES oven lamp.
So the series limiting action of these simple filament lamps is much more than 25W to 100W halogens I've tested before. A staggering 10:1 resistance change. The old iron wire and hydrogen filled barretters are even more impressive. I think I've one somewhere.
Most lamps are a coiled coil rather the the straight wires on these.
An EL34 ought to be tested in ita amp. It's about 90mA anode and 20mA screen. The FET in that situation would be off. Pa 25W The vg for cut off might be -40V
An EL84 is about 50mA anode max and 6mA screen max.
With two lamps in parallel and the nominal 300V supply and output at 150V and no load you might see about be 25W to 30W on the FET, but that's impossible due to the transformer limiting at 20W. I can't imagine more than about 8W to 12W worst case on the FET with no external load. Hard to say without plotting V/I for transformer rectified and R vs I or V for lamps.
Some actual measurements. lamps are rated 230V-240V
Cold (about 19 °C)
15W (small bayonet) 333 Ω
25W (small ES, old) 195 Ω
26W (small ES, new) 169 Ω
Hot @ 121.5V AC (based on measuring AC current)
25W (small ES, old) 1841 Ω
26W (small ES, new) 1599 Ω
Hot @ 235V AC based on wattage
25W (small ES, old) 2209 Ω
26W (small ES, new) 2124 Ω
Approx Current mA
Vs 25W 26W
30 27 44
40 32 48
50 35 53
60 43 --*
121.5 66 76 (Actually an autotransfomer. I only have insulated one screw holder, so didn't test the bayonet model.
[* can't read my note!]
So due to much hotter at rated voltage, the resistance swing is far more than for valve heaters.
The only new filament lamp in the regular shops now is the Philips 26W smaller ES oven lamp.
So the series limiting action of these simple filament lamps is much more than 25W to 100W halogens I've tested before. A staggering 10:1 resistance change. The old iron wire and hydrogen filled barretters are even more impressive. I think I've one somewhere.
Most lamps are a coiled coil rather the the straight wires on these.
