I trimmed the bias in my F5Tv2 up to 400mV across 0R5, oh man, how much flame and smoke this amp can produce! I guess, Nelson was right about a fire extinguisher For guys who are new in amp building be careful and let the amp heat up before adjusting bias high
bias runnaway at 0.8A pr device? Guess you have the diodes on the main sink, wich is very hot.
For guys who are new in amp building be careful and let the amp heat up before adjusting bias high
i would say: drop the diodes
No, diodes are out of the main think, but no heat thinks on them,but they are cold . I will try again tonight-tomorrow.
get some sinks on them. and watch the bias. you can also lower the source resistance, so that you get your bias with lower voltage drop.
be careful and let the amp heat up before adjusting bias high
For others, this may be the key sentence. These mosfets have a positive tempco, si if you bias them high while cold, when they begin to heat up, the bias will continue to rise. If you are not watching them, you could get in some trouble.
I trimmed the bias in my F5Tv2 up to 400mV across 0R5, oh man, how much flame and smoke this amp can produce!
Ooooh, pictures please
It is the same channel yes. However, I cascoded FE(1/2.2 of rail). I have to say, that after cascoding the amp became much more sensitive to turns of the trimpots. Do you think the cascode could cause th oscillations? But I tried it with 24V PSU and it worked.
Cascodes tend to stabilize, amps rather than make them unstable, as they provide more constant operating conditions. The Cascoded version I most recently built was on the store boards. Everythign checked out Ok.
It is possible, but the cascodes could have increased the bandwidth of the amp enough to create possiblity of oscillations. I would think you would have seen evidence of it in burned gate resistors, but i guess it could have been small enough to trigger burn. Perhaps ZM or someone has another perspective or opinion. For now, I suspect, too high a bias on startup and it just got away from you.
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