why am i reading 25v on every leg of my transistor?

[cooldude666]

Hello my friends,
I'm trying to build this preamp on my breadboard and am ripping my hair out trying to figure out why I'm seeing 25v on Q1's base, collector, and emitter. Anyone have any good suggestions of where to start? I checked my ground connections, they're solid. I've triple checked my resistors with a multimeter. I can snap a picture of my breadboard later but maybe someone has a fair idea of what to check for and why this isn't working at all. Would a bad transistor be manifesting itself like this? i can never remember the diode test so i haven't tried that yet. thank you for any assistance

[R.G.]

This happens when either the connections from base and emitter to +25 are much lower resistance than the other resistors trying to pull them down towards ground. This can be because of a very low resistance to +25 - like, say, a shorted solder joint, bad breadboard contact, wrong connection and so on. Or it can be that the resistors you think are pulling the base and emitter down are not really pulling them down - that is, one end or the other of the resistors is open to ground, not the resistance you expect.

Attack this by measuring the DC voltage on both sides of every resistor, and seeing if that gives a hint. If R6 and/or R7 has ground on one side and ground on the other, then they're not connected to the transistor. If they have ground on one side and 25V on the other, the resistor is open. If they both have the same problem, are they both plugged into the same little contact strip in the breadboard?

Breadboards are wear-life items. They flatly wear out and the contacts go dirty and loose with use. If you find a problem with a contact in a breadboard, THROW IT AWAY AND GET ANOTHER ONE. This will happen to all of them in time. For me, my hours tracking down a bum breadboard are purely a waste.

[reveal]

In college I taught a freshman level electronics lab.  One of the common mistakes was pushing the component wire so far down into the board that it touched one or more neighboring rows.  Good luck, its the simple things that can make you crazy.