So last night i was finishing up a little project that involved a solid state relay, it requires 600mA @ 7v, so i had my 12v source and a 10ohm 5w resistor in line, in order to drive it with an arduino im using a nte 261 npn, i know its an overkill but it was the only one with enough hfe i could fine locally, any way im driving the npn with a 3.9kohm that gives me enough mA to saturate the npn. On the breadboard it worked fine, so i solder it up on a pcb board , tested it and worked fine , call it a night today went to give it a final test before installng and nothing, i took mu multimeter to it the relay its getting voltage simultaneously to both terminals thous overheating the npn and the 5w resistor, i took the whole project back to the breadboard and its working fine but not on the pcb what gives.
I can only guess that the breadboard layout does not match the PCB ??
Its a stripboard, whats curious is that it worked flawlessly last night , i desolder all the components and tried it on the badboard and it works fine, im guessing maybe theirs a arch somewhere, under what condutions a transistor could saturate without a base current? cause thats what they are doing...
Ok, so i juat resolder the components with a pair of cs318 that i salvaged from somewhere, replace the resistor and its working fine, could 've been the casing the nte were to220 and were making conact , the cs are to92?.... I doubt it but ill ask anyway