One other thought about changing out the regulators.? ? 7805's are linear regulators, and the power they dissipate is the forward voltage drop (Vin - Vout) times the output current.? ? ?The? quiescent current is sunk through the regulator ground pin adds power but only represents 72 mW of power, it will stay cool unloaded.? If you can measure this quiescent current and it's around the standard 6mA the part should be OK.? ? ?You mentioned 290mA, so .290 x (12-5) = 2W, I've seen references state that you need a heat sink on a TO-220 above 1.25W.? ?The datasheet for the 7805 shows that 2W is about the MAX power dissipation without a heat sink, but that's probably pretty hot.? ? ?Changing the regulator, won't change the math on how hot the device is going to get if it's operating correctly.
Also, the TI datasheet for their? currently produced 7805 indicates that it has thermal overload protection.? So, if you have 5V on the output, it's still operating within it's allowable temperature range, otherwise it would shut down.? ?But, keep in mind, the maximum operating junction temperature is 125C, which is still hot enough to burn your finger.
73's Jim N8CAH
