Re: Brenell Purchases
Have now powered up and done some quick measurements, monitoring the HT voltage and current while slowly bringing up the mains voltage from Variac.
Only got to 150 volts mains with the HT current already up to 45 mA (highest I have seen it) and HT voltage 165, then the EL84 Output pentode started flashing/arcing internally, together with loud horrible noises from the speaker. Mains ripple also seemed higher than normal at around 400mV p-p.
Switched off and removed the valve and repeated. At 200 volts mains, HT voltage was 356 volts and HT current 3 mA and ripple 30mV, I think these figures are very similar to previous values seen with no EL84 fitted. I did not take the mains voltage up to 240 because the HT voltage was already at 356 volts and power supply capacitors only rated at 350 volts.
Not sure yet if the EL 84 has developed an internal breakdown problem or something to do with the external connections to the valve.
David
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