i dont mean to question you or anyone else who is more educated in this than i am but after reviewing the board i have and the original circuit design it does seem that they are backwards now. please put my mind at ease as to why they arent now
fligti91 said:
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 🙂
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?
fligti91 said:
Yes, that's correct.
Easy solution, just turn P1 while you measure the voltage on the drains.
Magura 🙂
fligti91 said:
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:
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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