Help a n00b debug his dead MosBoost

[stuartgsmith]

Howdy folks, this is my first build:
Mosfet booster from Tonepad's schematic on perfboard.

Problem: I get a bypassed signal, but nothing when the effect is on.

I've measured the voltage where it enters the board, and it is really low (like 0.45V or something)
From the various debugging pages I've read, this could mean either a short or a bad component, right?
Or maybe cold solder joints?

I made a diagram of the results of my audio-probing:



This made me think it was the transistor, so I tried another one (I bought two of everything, just in case) and got the same results.

I'm stumped, and I don't know what to do other than start over from scratch.
Anybody have any insight, advice, tips, tricks, voodoo?

[petemoore]

See if the + is connected to the - at battery clip...indicates direct short.
 Transistor orientation can be tricky on this one. Check the Data sheet of the transsistor youre using...then rerecheck that it's connected to the circuit where they're supposed to.
 .45v of a nine volt...[  ]
 Connect the DMM black to ground of circuit, then poke around with the red lead looking for connections to ground that shouldn't be with no battery conected.

[lightningfingers]

Did you use a socket for the MOSFET? They are very easy to upset, they will gleefully crap out on you if you don't hold em right, let alone solder them right to the board...

[stuartgsmith]

petemoore: Thanks, I'll check the wiring.  I should be checking for resistance, right?

lightningfingers: Didn't use a socket.  Good idea though.  What do you mean by "not holding them right"?


I am determined to get this thing working!

[Mike Burgundy]

A MOSFET can die by not holding it right - if you have the wrong sweater, and touch one of the leads to it, static electricity can kill the MOSFET. No kidding.
The signal obviously is not getting past the MOS, so either it's fried or orientated wrong. All datasheets I have on a BS170 state something like "Note: different pinouts available" so beware.
If youre not sure, take out your multimeter and clamp its - lead to what you think the source is. Use a screwdriver, clipped off component lead or something to briefly short out gate and drain.Set your DMM to resistance. touch the drain with the + lead, should read VERY high resistance - MOSFEt is "off"
Now touch the + lead to the gate, and the to the drain: should read "on" or low resistance. If this works, the tranny is ok, and the pinout is right too. If it doesn't either the tranny is dead or the wrong pinout is used. Some puzzling should solve that.
hih