hi all
I have a question, can a mosfet 2sk1058-j162 blow themsself if oscillating?
she did and the gate resistors did smoke, first I thought because of the plus 120 volts from driver did this but that is not the case, also with driver off it did kill the resistors, and now the 2sk1058 is short circuit.
A little learning here, I do like, the mosfets came from china, maybe she were bad also, pins were oxidated on egde of housing.
thanks
I have a question, can a mosfet 2sk1058-j162 blow themsself if oscillating?
she did and the gate resistors did smoke, first I thought because of the plus 120 volts from driver did this but that is not the case, also with driver off it did kill the resistors, and now the 2sk1058 is short circuit.
A little learning here, I do like, the mosfets came from china, maybe she were bad also, pins were oxidated on egde of housing.
thanks
the mosfet housing is oke, it is not blown appart.
just short circuit after big oscillation.
I try now verticals.
The reason I'm asking for the picture is that we might be able to say if it's a fake. It will also help others to identify a fake part. There is another long thread about fake parts on this forum ! So if you can put up a picture it will be useful to others.
The oscillations could be just because it isn't up to spec and prone to oscillations. MAYBE ! Just make sure your part IS a fake ! If it's genuine then others will need to see how you are using the MOSFET. A circuit diagram will be helpful to give an opinion.
The oscillations could be just because it isn't up to spec and prone to oscillations. MAYBE ! Just make sure your part IS a fake ! If it's genuine then others will need to see how you are using the MOSFET. A circuit diagram will be helpful to give an opinion.
tho blown ones are 2sk1058 and 2sj162, now I have put in (as test i will use laterals if I have them again). 2sk1530 and 2sj200, she do work, no problem but I have put extra gate protection diodes.
I did see that as there is oscillation there can be high gate voltage.
but here is schematic. if the drivertube is cold, there is high voltage on the mustage fet drain normally no problem but a supple who give voltage as the tubes is warm is better, also for the tube.
as you see in schematic gates are dc coupled to the 6C19p and his mu mosfet.
thanks.
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Yes guys I now that, the printed circuit is made so both can installed. but I use normally only laterals, but she died and I have not others yet. I can do both, only the 2sk1530 has no gate diodes and so I put them in, with a servo the voltage will not be high if the driver tube is not warm yet.
Amp works by the way, now make quick a servo because a tube is not so stable one.
Amp works by the way, now make quick a servo because a tube is not so stable one.
I do make pictures if I find them, the 2sk1530 is also blown yesterday, also this one did unstable motorboating and bam, simulating the amp is oke, no problems.
schematic here, the voltage preamp is not present, problem was with mu mosfet 6c19 and only with speaker connected, strange behavior not in simulations but maybe I am not so clever as I look, the most difficult things are the simpel ones.
Left is the vertical 2sk1035 mosfet, where the print is already gone, and left the lateral mosfet, other two of them are in a amp playing with no problems, the pins however breaks instantly if bend, that is what I did discover a while back.
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I have test the amp without mosfet voltage removed the fuses and this is what I get beatifull square wave, 20 Khz 120 volts pp.
If i did use the fets, I get strabge things, like pang pang from the speaker if I gave more output, and motorboating, very strange, I afree that it can be easely fakes, or more prone to oscillations because of the two inverting stages before the fet, but it will be challenge otherwise live is boring.
tomorrow I get the lateral fets, I have do a resistor from the mu fet to ground because of the high impedance of the fet input.
If i did use the fets, I get strabge things, like pang pang from the speaker if I gave more output, and motorboating, very strange, I afree that it can be easely fakes, or more prone to oscillations because of the two inverting stages before the fet, but it will be challenge otherwise live is boring.
tomorrow I get the lateral fets, I have do a resistor from the mu fet to ground because of the high impedance of the fet input.
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I have found it, capacitor C2 470 nf now 2.2uf has be damaged with soldering, and so leaks voltage to the fet gate, that is why it did so strange behavior, now it works, I have removed the fets, and replaced the capacitor, the gate protection diodes on the mustage fet side did blow some times and I where not capable to find the reason, now it was the capacitor, so i have to be carefull next time to not to burn the capacitors with the iron.
Now I can find out of a plate follower wil work better as driver then a cathode follower, I have still use the 6c19n driver because it is low nu and low plate resitance, sound it really better with the voices and violens a less sharper and sweeter.
Now I can find out of a plate follower wil work better as driver then a cathode follower, I have still use the 6c19n driver because it is low nu and low plate resitance, sound it really better with the voices and violens a less sharper and sweeter.
wel after a time testing, it do work, use a double platefollower, one for foltage amplification and one for driving the mosfets in plate mode with a mu follower above, voltage follower has mu of 20 and second a mu of 2.5 for working without feedback.
Reason for this approach is a guy who say that a cathode follower do not sound as wel as a plate follower, it do indeed give a very nice natural sound, warm and groovy.
regards
kees
Reason for this approach is a guy who say that a cathode follower do not sound as wel as a plate follower, it do indeed give a very nice natural sound, warm and groovy.
regards
kees
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