fligti91 said:so what of the q3's? the drains on both sides were at about 22-23 volts before it blew
@half of input. am i correct that the mpsa92's are backwards?
The mpsa92 are not in backwards, we checked that Friday, remember?
Magura
fligti91 said:how many volts do you have at the gate of your q2?
No idea, never felt the need to check it.
I am fairly confident that you have one channel that is working, and the other channel died due to heat.
Magura
fligti91 said:ok, ill trust you on this and hope to god your right. ive put in my last 9240 for q2 so.....
So, any smoke?
Magura
fligti91 said:is p1 to set the drains at half the input? if so what direction to turn the pot to rise the voltage at the drains?
Yes, that's correct.
Easy solution, just turn P1 while you measure the voltage on the drains.
Magura
fligti91 said:no smoke and sink is heating up. im so f'n pumped right now!
Now keep an eye on the temperature of the heatsink, don't let it get warmer than you can touch it for a second or so.
Magura
Magura said:That is not much for two channels. You are going to dissipate close to 300W of heat, if you stick to the 0R22, as in 3A bias.
I used something like 6 or 8 times that, and still I had it running at the wrong side of good.
Magura
I think you need to turn the bias down by x2 or even x4 until you get better heatsinks. Mebbe 1 ohms for the bias setting resistor (up from .22/.33)
well i still have the question as to why im getting voltage in the 30's to the gate of q2
im being told that its ok but im thinking there is a reason why mr. pass said it is supposed to be 4 volts to the gate of q2. im thinking q2 is going into overdrive because of the gate voltage. what do you think?
im being told that its ok but im thinking there is a reason why mr. pass said it is supposed to be 4 volts to the gate of q2. im thinking q2 is going into overdrive because of the gate voltage. what do you think?
I just looked at the IRFP9240 datasheet
http://www.irf.com/product-info/datasheets/data/irfp9240.pdf
Two things pop out:
Maximum source-gate voltage is 20V. You measured 0V on the gate which means you blew out the gates.
The gate threshold voltage i.e. where the FET turns on is -4V. You measure this from gate to source (not gate to ground)
But you've got one channel going well?
http://www.irf.com/product-info/datasheets/data/irfp9240.pdf
Two things pop out:
Maximum source-gate voltage is 20V. You measured 0V on the gate which means you blew out the gates.
The gate threshold voltage i.e. where the FET turns on is -4V. You measure this from gate to source (not gate to ground)
But you've got one channel going well?
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