Re: 2N2222A getting super hot


Ted
 

Joe,

RV1 & 2 "can" be brought up to more than 100ma each, at the cost (very possibly) of toasting your IRF510 final output devices :)   I don't recommend it.

Like yourself, I note the 2N2222 replacements in the predriver and driver getting warm. My "warm" may be your "hot" due to perspective, maybe not. Can you keep a finger on it for 10 seconds without experiencing real pain?   If you get a genuine burn injury,  it's probably running hot; my suspicion is that, as this is a terribly common upgrade,  a bit warm or very warm is just fine.

As an explanation, follow the circuitry.  Those transistors are basically shorting 12 volts to earth/ground at an RF rate, save for the 11-ohm resistors that govern the process.  The result at each point is to take a sample of the stage before it and make that energy "wiggle" the next transistor, whose job it is to almost short out the next stages' 12-volt feed at an HF frequency rate. Virtually draining B+ current through the resistor creates heat (how an oven works, etc etc). The whole reason for swapping the 22-ohm resistors for 11-ohm chips is that the 2n2222 can handle the greater workload - the more direct conduct of B+ to ground due to reduced resistance  - and delivers greater output as a result.  That more heat is produced, should be expected within reason.

Hope this helps.


Ted
K3RTA

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