EL84 cathode current too high!

    Hi! I have builded a J5Mk1 months ago. After a lot of time of good working, I started to hear some "craks" in speaker.
    I have checked again all the voltages and are OK.
    Here are:
    Pin 9=292V
    Pin 7=302V
    Pin 3=10,6V
    Resistor between Pin 3 and ground is 237 Ohm. So, for the Ohm law, the current should be 44 mA.
    INSTEAD, I HAVE 120mA at the cathode of EL84!!! How can I lower the current on the cathode?

    Re: EL84 cathode current too high!

    Hi,

    Zitat

    Pin 3=10,6V
    Resistor between Pin 3 and ground is 237 Ohm

    10,6 V/237 Ohm = 44,73 mA.

    How did you measure a current of 120 mA? ???

    Bernd

    Jaichweiß (Andy Pipkin)

    Re: EL84 cathode current too high!

    I have read this with 2 multimeter, one of this digital and the other analogic. And The value is the same: 0,12 Ampere.
    It's strange for me too, and I don't know how this can be possible.
    Maybe I have to test another value, but witch?

    Re: EL84 cathode current too high!

    are you sure you didnt check the current in parallel with the resistor?
    if so, the resistance of the multimeter would be very small compared to the 237ohm resistor, giving a higher current through the tube!
    when you measure current, you have to plug the meter in series with the resistor!

    Re: EL84 cathode current too high!

    :-\ Yes, I've checked the current in parallel. But the resistor is wired with one lug to the tube cathode and the other one to ground.
    So, how can I measure the current in series? I don't know!

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