BMP transistor voltages...not good at all

[lightningfingers]

even i know these are bad, but what is causing this badness?

Q1
c 4.64
B~0.5
E 0

Q2
C 8.75
B 0
E 0

Q3
C 0.03
B -4.5
E 0

Q4
C 0
B 1.7
E 1.14

whoooo i've really screwed something up, any one got any measurements from a working Big Muff so i can compare?

[petemoore]

Look for soemthing that involves all these connections like ground fault or 9+ being missed somewhere...I do that about 1/3 of the time...forget a 'major' connection by doing the 'minor' ones first...[major/minor is an army guy that digs up metals...lol..all connections need to be made 'right, as we well know,  for the circtuit to function as stated in schematic].
 Yes somethings awry with those readings, something simple I suspect...only time and debugging will tell for sure... :arrow:

[niftydog]

Q3
B -4.5

Que?

That's impressive...

Double check resistor values and orientation or transistors etc etc.

There's something majorly wrong, and I doubt its those zeners!

Get out the multimeter and measure those resistors... OUT OF CIRCUIT!

[R.G.]

Q1
c 4.64
B~0.5
E 0

That one's pretty normal.

Q2
C 8.75
B 0
E 0

Base shorted to emitter or ground.

Q3
C 0.03
B -4.5
E 0

Mismeasured (i.e., maybe multimeter - lead on +9V) and there's something wrong in how it's hooked up. Can't tell til the measurement makes sense.

Q4
C 0
B 1.7
E 1.14

This one *might* be OK, but the collector is mismeauredm, most likely.

Clip the black (-) lead of the DMM to a single  ground place and leave it there while measuring the positive voltages on the other places.

For reference, read the "Guitar Effect Debugging Page" at GEO, with particular attention to the voltages that a bipolar transistor must have to be working as an amplifier. For an NPN, the collector must be the most positive pin, by a significant fraction of the power supply voltage; base is next lower and the emitter lowest. The base must be 0.4 to 0.7V more positive than the emitter. If those are not true, the transistor can not be amplifying. This knowledge will eliminate the need for specific comparative voltages in most cases.

[lightningfingers]

okay lets have another go at these voltages,

I think Q1 is OK I can get clear signal there with the audio probe

Q2

C 8.62
B 0 (it's not shorted to ground or the emitter, is this one broken?)
E 0

Q3

C 4.66
B 0.6
E 0

Q4

C 4.68
B 1.4
E 0.8

[R.G.]

C 8.62
B 0 (it's not shorted to ground or the emitter, is this one broken?)
E 0

Hmmm... OK, there's another way this could happen. If the base is open, getting no DC through the 470K resistor to the collector, this would be one result. Is that 470K from collector to base open? Bad solder joint? Broken PCB trace?

[Chris Goodson]

Is it possible Q2 is dead?

[lightningfingers]

is it possible Q2 is dead?

thats what happened. thats never happened before, how likely is it for transistors to die?

[niftydog]

well... it happens.  You might have just got lucky with that one and picked up a dud.

Yet to be assured of this phenomenon, but it could have been static electricity!  :shock: