When connecting the amplifier it does not turn on and consumes more than 7 amperes without load, disconnect the loads one by one and detect a possible short, all the power section transitors were disconnected, and the equipment turns on, a mosfet transistor was discovered in short j111, The detail is that when you reconnect the power transsitors and stop turning on the equipment, when making some voltage measurements it is detected that in the gate terminal of the section that is fed from the positive +35 v of the mosfet there are 15 volts, some suggestion.
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Are you sure that the J111 jfet is shorted. They read as being leaky, compared to other transistors. That's normal.
Are you sure that the bias current isn't set too high?
Are you sure that the bias current isn't set too high?
As I verify the bias current ?, normally in amplifiers with quasi-complenmetary transtors the bias current is verified by measuring 0.7v base to emitter but in mosfet I don't know if it is the same.
I've never heard of setting the bias as you described.
Set the pot fully counter-clockwise. Does the idle current drop?
If the amp is drawing excess current, it's best to be working through a current limiter and with the FETs clamped tightly to the heatsink. Some JL amps are sensitive to low-voltage so a limiter may not be possible on this amp.
Set the pot fully counter-clockwise. Does the idle current drop?
If the amp is drawing excess current, it's best to be working through a current limiter and with the FETs clamped tightly to the heatsink. Some JL amps are sensitive to low-voltage so a limiter may not be possible on this amp.
That's not how you set the bias.
I'd set it at 1mv (0.001v) across the source resistors. if you can't access the terminals of those resistors, I'd set it at the point where the idle current draw just barely increases.
I'd set it at 1mv (0.001v) across the source resistors. if you can't access the terminals of those resistors, I'd set it at the point where the idle current draw just barely increases.
you know what the function performed by jfet j111 since it was the transistor that was shorted from drain and sourse,
maybe that's where the problem stems
maybe that's where the problem stems
if it reduces it, but there is no change I think about replacing the power transistors there are a number of better than the irf540 mosfet
the current of vias is correct 25 mV I changed it to 100 mV and the problem persists, but I started to check mosfet one by one and there are two that in the dynamic test the 12 v bulb does not turn off (the dynamic test that I perform consists of in putting a 12 volt light bulb in series to the drain of the mosfet and the ground to the source and with the pure fingers exiting the mosfet, to close the circuit together with the fingers the drain and gate and to open the circuit together with the fingers the source and the gate). Well I continue with the explanation by performing said test there are two that do not turn off correctly, with the multimeter they mark apparently well.
With the meter set to ohms, what's the resistance between the gate and the other two legs for the FETs that you believe are defective?
The measurement with the multimeter are the following with it pointing positive at the gate and the infinite drain and gate at the infinite source only marks a measurement, with the negative tip on the drain and the positive tip marks 508 ohms
What if you reverse the probes?
What readings to you get with both probe/terminal configurations on diode-check?
You need to short the gate to the source leg to ensure that the FET gate is not charged.
What readings to you get with both probe/terminal configurations on diode-check?
You need to short the gate to the source leg to ensure that the FET gate is not charged.