They are in parallel and both are 20 ohms. I'd suggest increasing the value and using a larger through-hole resistor (properly fixed to the adjacent cap) for power dissipation if there is any sign of overheating of the voltage regulators in the class D section. This resistor drops the voltage from the -20v supply and the two 20 ohm resistors need to drop more voltage to let the SMD regulator transistors run cooler.
I replaced both resistors for 1x 10 ohm.
Powered up, but direct in protection
Removed both the rectifiers MUR1620 (for high voltage) and amp is powered up normal, PS seems to be ok.
Put back the rectifiers. Then removed all output mosfets 8x IRFP3415 (measured all ok), after power up, still in protection.
Good ideas and schematic diagram are welcome, thanks in advance.
Powered up, but direct in protection
Removed both the rectifiers MUR1620 (for high voltage) and amp is powered up normal, PS seems to be ok.
Put back the rectifiers. Then removed all output mosfets 8x IRFP3415 (measured all ok), after power up, still in protection.
Good ideas and schematic diagram are welcome, thanks in advance.
Pull out rectifiers, powered on normal with output mosfets removed.
Gate pulses are there on the output mosfets, but on one pair I see pulses with negative polarity and like a very small spike. Gatedriver transistors MPSA56/06 are good, diodes ok...
All measured against ground.
Is this normal, or what should the gatepulses look like?
Gate pulses are there on the output mosfets, but on one pair I see pulses with negative polarity and like a very small spike. Gatedriver transistors MPSA56/06 are good, diodes ok...
All measured against ground.
Is this normal, or what should the gatepulses look like?
This amp is working ok again, the problem was that when starting up there was a big spike on the bench power supply (analog 10A) , which causes a voltagedip. That was enough to switch-on-off-on the internal power supply in the RF.
Never had that with other amps with the same analog power supply.
With attached some extra filter capacitors in the RF it worked ok. Measured the original filtercaps, railcaps on ESR and capacitance but they were all ok.
Never had that with other amps with the same analog power supply.
With attached some extra filter capacitors in the RF it worked ok. Measured the original filtercaps, railcaps on ESR and capacitance but they were all ok.
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