Re: The "Sussex" Homebrew Valve Tester.
Hello Mike G4WYZ,
When you were suggesting an alternative MOSFET you wrote - 'Which are rated at 800 volts at 2.5A, this explains why they run cool, requiring no heat sink.'
They will only run cool if they are passing a small current or dropping a small voltage.
If you test an EF86 at 4mA at 250V they will run cool.
If someone tries to test a power valve at low voltage and high current, the MOSFET in the anode regulated supply will get hot. It will need a heatsink.
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