robb wrote:
"clifto" wrote...
robb wrote:
I connected the 5v (through 450 Ohm) to the PCB 5v and 0v lines.
i measured ~60 mA curent nothing warmed ...

That's pretty good. If you then shorted the PCB 5V and 0V lines, you would
have 450 ohms across 5V and should read 11.1 ma.

i idecremented the
resistance by 100 for each iteration of testing the measured
currernt increased slightly until i made it to (100 Ohms) and
then the current spiked to ~+ 1.5A and the 7805 fried ?

To get 1.5A through 100 ohms you need to apply at least 150V to it.

thanks for reply clifto,

i will have to believe you on the numbers

and although the numbers may seem incorrect from a electronic
formulaic analysis i can only report what i see on the equipment
i use and with the setup i use.

What I was trying to get you to realize is that there is probably a
problem with your equipment, or with your understanding of its use.
When the PCB supposedly draws over five times as much current as a
dead short, it should tell you that what you think you're seeing isn't
what is actually happening.

The DMM amp reading numbers were fluctuating wildly on my last
test and 1.57 ???was something i thought flashed by as highest #
maybe it was .57 but i do know that whatever the number the 100
ohm resistor had a stream of smoke going up and the 7805 appeared
to have a puff of smoke released before i could dis-connect now
i am hopping somebody can help me decipher what went wrong with
my testing

If you used a 1/10 watt 100 ohm resistor, putting 5 volts across it
should dissipate 2-1/2 times its capability, or 0.25 W. That might
make it release smoke.

--
Angry American flags attack Hillary Clinton!