Iron Butterfly fuzz wah.

[digi2t]

I think it's a kind of a cool way to combine a tone control, and volume, all in one. It's a new one to my noob eyes.

I'll have to try different pots tonight. Thanks guys!

[Gus]

I just ran a sim for the DC voltages of the fuzz transistors

Are you getting about .6VDC at the collector of the first stage?

Are you getting about 6VDC at the 2nd collector at one end of the dwell rotation and about .6VDC at the other end of the dwell rotation?

Transistor hfe does not seem to matter much in the sim. I tried 2N2222s and 2N5089s and the collector voltages were close in the sim

[digi2t]

I just ran a sim for the DC voltages of the fuzz transistors

Are you getting about .6VDC at the collector of the first stage?

Are you getting about 6VDC at the 2nd collector at one end of the dwell rotation and about .6VDC at the other end of the dwell rotation?

Transistor hfe does not seem to matter much in the sim. I tried 2N2222s and 2N5089s and the collector voltages were close in the sim

I'll check that tonight, and report back.

[digi2t]

I just ran a sim for the DC voltages of the fuzz transistors

Are you getting about .6VDC at the collector of the first stage?

Are you getting about 6VDC at the 2nd collector at one end of the dwell rotation and about .6VDC at the other end of the dwell rotation?

Transistor hfe does not seem to matter much in the sim. I tried 2N2222s and 2N5089s and the collector voltages were close in the sim

1.017v for the first stage collector.
0.6 at minimum dwell, 5.45v at max dwell, for the second stage collector.

Both transistors are 2N3904's.

[Gus]

Thanks for the voltage readings.  The sim does not show about 1VDC unless I reduce the first stages collector resistor value if I use 47K in the sim it shows about 1VDC.

Could you check if you used a 47K in you breadboard at Q1 collector?  The pictures posted look like 470k at the two fuzz transistors. 

I added the tone section to the sim it acts like you posted

[Gus]

sim

[digi2t]

Strange that the voltage doesn't line up with the sim, but both C resistors are 470K on my breadboard. Got 1v on the first stage collector.

[Gus]

Could you swap the transistor positions and measure again? 
The 2N2222 model sims the same as measured with circuits I have built.

[PRR]

Rc and Rc are the same 470K. But Rb has 1/100th the current of Rc and should show 1/100th the voltage drop. Say ~~8V across Rc, and 0.08V across Rb, plus Vbe, is what Gus said: 0.6V at collector.

Alternatively hFE is super-low, like 10. But that is super unlikely for modern Silicon.

OTOH: if E and C are reversed, the transistor will "work" (for low voltages) except reverse-hFE will be super-low. 1 to 10 instead of 50-500. hFE of 20 gives the numbers digi2t reports. That seems high for a reverse-hFE, but this is poorly controlled in production (because never specified), so maybe?

Overall: with the 470K resistors we must account for Meter Loading. A 10Meg meter would seem to cause readings about 5% low. Not that bad because transistor action stabilizes the voltages. However a 10K/Volt needle-meter would suck everything down enough to make readings dubious.

[Gus]

A thread
http://www.diystompboxes.com/smfforum/index.php?topic=92997.20

Any update? 

The dwell control looks like fun

[digi2t]

Sorry Gus, but work has weighed me down this week. Going to piece together the wah section this weekend.

As for the collector voltage on the first stage, I swapped in a couple of BC149's, and I'm still getting around 1v on the first collector. I'm using a Wavetek Meterman Model 235 DMM.

[Gus]

Just wired up a 2N2222 with about 200 hfe with two 470Ks like the first stage

I got the .6VDC at the collector

The reason I did that is your voltage reading.

Can you try a different part of your breadboard and measure the resistors with a meter?  Maybe the base to ground resistor is mis-marked?

[LucifersTrip]

I got the .6VDC at the collector

exactly...just measured the last si Fuzzrite I finished, .63V at each collector with 9.6V supply.

[pinkjimiphoton]

Groovy man.

Friends just saw The Iron Butterfly Experience at a campground on the outskirts of Ventura. They believe they saw "former members". It's possible: apparently there have been 70 people played as "Iron Butterfly", not just Ingle Bushy Dorman and Braunn.

it's funny, i saw an IB alumnus at the gig last week, john catalano. small world

nice find dino, i eyeballed this on ebay myself a few times

[digi2t]

OK, I finally got a video done. Fuzz alone first, and then fuzz wah together.

Doesn't sound half bad. Got that old school fuzz feel to it. I think it's almost worth sticking into a wah shell... if I had one to spare.

EDIT:

Here's an updated vero. The first one had errors, and this one is a tad smaller as well.

[pinkjimiphoton]

dino, i have a box coming your way soon, do you want me to stick a wah shell in there for ya ?

[digi2t]

dino, i have a box coming your way soon, do you want me to stick a wah shell in there for ya ?

PM'd. 

[pinkjimiphoton]

pm's back, i hope to get it out this week. just waiting to make sure the whole mouser order is in.

[digi2t]

Owner of the unit on Ebay was kind enough to reply to my inquiry as to whether my breadboard test sounded close to the original. To quote...

"Sounds pretty amazing.  You nailed it.  Only problem is that you don't need mine now! Ha. Great job!"

Seeing as how I seem to have developed a knack for finding old console organs for free, a nice Yamaha has recently donated it's guts to me. Lots of 2SC828, 2SC644, 2SC1000, and even a few 2SK30 fets to be had here. Not to mention all the mojotastic caps, diodes, and resistors. Even a few inductors. I'm going to redraw the vero for the bigger parts, and 2SCxxx pinouts. Going to do another free cycle build here, like I did for the Burnski Buzzaroundski build.

[Time River]

@digi2t,
Thanks for the pics and diagrams.   I have had one of these pedals since the 80s.   It has some problems and your work will definitely help.   Now that I have seen your pics I think I will dig out the pedal and try to figure out what is wrong with it.  Many thanks for your work!
Kevin