Fender Blender debug help please.

[newfish]

Hi All,

Finally bit the bullet and built a 'Blender' - and I have no signal passing with the effect engaged.
Signal passes with the effect disengaged.

I built the pedal from this layout / schematic...

http://fuzzcentral.ssguitar.com/blender.php from a PCB made to Bill Lawrence's layout.

All transistors are 2N5088, with 1N60 diodes in all positions.

Voltages are as follows with a reasonably fresh battery...

Q1 C 8.7 B 1.3 E 1.0
Q2 C 9.2 B 8.7 E 8.5
Q3 C 6.1 B 3.3 E 3.0
Q4 C 1.6 B 1.2 E 0.6
Q5 C 8.9 B 0.5 E 0.02

I've had an audio probe on this circuit, and have traced signal through from the input socket through to the base of C1 - and this is where it stops.

I've checked / measured all resistor values - and they appear to be correct, as do transistor pinouts.

I've also pulled Q1 and Q2 out and have checked their respective DC gains - both are around the 380 mark.

My gut feeling is the biasing of Q1 / Q2 (very little difference between B and E on both transistors).

I'll re-check the resistor values once I'm home from work - but any extra eyes / opinions would be gratefully appreciated.

Cheers!

Ian.

[GibsonGM]

Do you mean base of Q1?   Have you made SURE of the transistor pinout???   If no signal with the transistor removed, you probably have a short to ground right there.   

Q1, Q2, Q3  base>emitter voltages look odd, only a couple millivolts difference where you should have about .7v.  Check all your stuff up to the 10u cap...resistor values, connection quality, basic errors.   Biasing may in fact be involved here, but be sure you have signal AT the socket with no transistor in...work your way from Q1/Q2 out and see what you get...

[duck_arse]

we don't get many blenders around here, I wonder why that is.

I have a circuit with original part #'s from somewhere on the wires, and hard to read voltages marked. it says Q1 should be C=4V7, B=0V2?, E=0V15 and Q2 9V, 4V7, 4V0. Q4 voltages also look out, w/ C=4V, B=?, E=0V39.

so something around the first 2 tr is bad. you should be able to figure the proper volts Q3, 4, 5 from the resistor strings on their bases.

photos?

[....slow typing]

[newfish]

Do you mean base of Q1?   Have you made SURE of the transistor pinout???   If no signal with the transistor removed, you probably have a short to ground right there.   

Q1, Q2, Q3  base>emitter voltages look odd, only a couple millivolts difference where you should have about .7v.  Check all your stuff up to the 10u cap...resistor values, connection quality, basic errors.   Biasing may in fact be involved here, but be sure you have signal AT the socket with no transistor in...work your way from Q1/Q2 out and see what you get...

I've checked my pinouts half a dozen times - and am convinced they're correct (reverse capital 'D' with Collector to top).
Something's definitely amiss with Q1 / Q2.  I'm now suspecting the 47K resistor of Q1's Collector - but will check this evening when I'm home.

Thanks for your input folks - this is by far the most complicated project I've attempted in a while, and I appreciate your time.

Cheers!

[hellwood]

double check to be sure that ALL of your grounds are good and connected to each other. I would also make sure Q1's emitter to ground through the 1k5 is not bridged to its base and Q2's emitter between the 560k and 120k resistors as well. I also might make sure the sustain pot lug to ground resistor is 680 and not 680k. oh well, these are the kinds of mistakes I might have made. I hope this helps...

here are some notes from my build, and this pedal is insane! You will be stoked when you get this thing up and running!
Q1 - (100Hfe)
Q2 - (147Hfe)
Q3 - (160Hfe)
Q4 - (171Hfe)
Q5 - (280Hfe)

Q1 -   c.5.07
         b..682
         e..114

Q2 -   c.8.74
         b.5.07
         e.4.43

Q3 -   c.6
         b.3.35
         e.2.74

Q4 -   c.3.27
         b.1.09
         e..450

Q5-    c.5
         b..902
         e..306

[newfish]

double check to be sure that ALL of your grounds are good and connected to each other. I would also make sure Q1's emitter to ground through the 1k5 is not bridged to its base and Q2's emitter between the 560k and 120k resistors as well. I also might make sure the sustain pot lug to ground resistor is 680 and not 680k. oh well, these are the kinds of mistakes I might have made. I hope this helps...

here are some notes from my build, and this pedal is insane! You will be stoked when you get this thing up and running!
Q1 - (100Hfe)
Q2 - (147Hfe)
Q3 - (160Hfe)
Q4 - (171Hfe)
Q5 - (280Hfe)

Q1 -   c.5.07
         b..682
         e..114

Q2 -   c.8.74
         b.5.07
         e.4.43

Q3 -   c.6
         b.3.35
         e.2.74

Q4 -   c.3.27
         b.1.09
         e..450

Q5-    c.5
         b..902
         e..306

Perfect!  Thank you so much.

There was a crack in the trace between the emitter of Q1 and the 1K5 resistor - so the emitter itself was floating.  A quick 'component leg bridge' later, and this monster roared into life.

Thanks once again for you help folks!