i had my lighting circuit and my regulator for my BT connected and i wanted to measure if there was any drop in voltage from the regulator. i should have just left it alone. i pulled out the x505, no physical signs of damage, still comes out as a NPN transistor in the component tester. i wonder, does zener d505 have a glass case? i wonder if it popped and that's what made the sound? i remember last time i smelled this smell, i cooked a zener once. but it could also be a ca or resistor getting hot. i tested the caps nearby in the circuit diagram and their ESR was fine. the only thing i notice, and i'm not sure this was the case before because i never checked, x505 kinda gets hot while playing a cassette, mms on, and about 70mA from my led/BT circuit. if you hold your finger on the metal back of the x505, it starts to hurt in about 5 seconds. i heard a rule for silicon transistors is that if you can't hold on to the plastic part of the package for at least 3 seconds, it's running too hot. i don't know. it the heat normal in this case?
P.S, this was supposed to be done last week. i had an issue though. i employed npn switching to control my light control system and when when i hooked up my BT and switched the npn off, the power fed back though the audio ground and cooked my BT module. it took me 2 modules to figure out what was happening. the circuit worked great until i hooked up the audio. lol.
i redesigned my light control circuit and now i am using pnp transistors so the switching is done on the high side so the ground is always connected which should prevent the current from feeding back through the audio ground of the BT module and cooking it.
i rigged up a system where there is only 1 button, the dial lamp button. initially lights are off. 1st press, dial is illuminated white with vu meters white. 2nd press, vu meters are white, left side of the dial is white, right side of the dial is blue, 5v regulator turns on and bluetooth is on. 3rd press goes back the the default position with lights and bluetooth off.
just waiting for my other BT modules to arrive. the whole circuit i made should use under 90mA off the X505 rail.