weeper wah

[jmasciswannabe]

Ran across one that is only working as a volume pedal. Never been modded or tampered with. All wires intact. Looks pretty similar to your average wah circuit. Uses 3094 transistors and a 1m pot. From waht I have read the problem could be in Q2, the cap after it or the pot. I was wondering if anyone had any other suggestions. I went ahead and took some readings on the transistors, but I can't interpret them.

battery voltage 9.18
Q1 e - .084 b - .69 c - 4.7
Q2 e - 3.23 b - 2.80 c - 8.84

Any suggestions would be appreciated! Also, I plan on drawing up a schem and a layout because I didn't find any around here. I will have to check to see if it is in production before I do.


Thanks
Ian

[petemoore]

It's probly an PNP Pos Gnd?
 In which case this one
 Q2 e - 3.23 b - 2.80 c - 8.84
 looks off because the base must be a diode drop at least above the emitter. This emitter is sitting between the E/C voltage bias.
 ... about that without looking at the schematic.

[jmasciswannabe]

pete, thanks a ton for the response....swapped it out with a nte123 similar voltage readings and still the volume without the wah..what else component wise can go bad to cause a problem like this?.....there is one electro cap, maybe I will experiment with that.

[Jaicen_solo]

From what I remember, if the inductor is disconnected, or if the part of the tuned filter is open that will cause the wah to produce a volume effect. Something to do with loading the output if I remember correctly.
I think it was the Tech of... article, I'm just of to check.

EDIT: Ok, I just checked. If the inductor is reading ok, then it probably is the large cap to ground which is connected to the inductor that has failed. Since they're usually electrolytic it's a common fault.

[Paul Marossy]

If it's anything like the Cry Baby circuit, if that 4.7uF cap is bad, you'll end up with a volume pedal...

[jmasciswannabe]

Hey Paul! You get my pm? Thanks Paul and Jaicen...thats where I was heading next! I got my fingers crossed!

[Paul Marossy]

Hey Paul! You get my pm? Thanks Paul and Jaicen...thats where I was heading next! I got my fingers crossed!

No, actually I didn't get your PM...  

[jmasciswannabe]

paul, emailed ya bro! for everyone else, yes replacing the 4.7electro fixed the no wah only volume problem. worded so other searchers might find it easier

how I missed the common wah problems under the technology of wah article, I will never know. I think I read all the way up to that part and then fast scrolled past it..... :oops:

[Paul Marossy]

Cool, glad you were able to fix it.  

[jmasciswannabe]

I was going to write up a schematic for the Dearmond weeper wah, but shortly after beginning realized that I would be waisting my time. Its the exact same circuit on the technology of wah page except for the 82k is a 100k. Also, the weeper wah uses 3906 transistors and a 1M potentiometer.

[Paul Marossy]

So, it's basically a Vox wah circuit with a 1M pot instead of a "100K" pot and one changed resistor value. Cool, thanks, I was wondering about that circuit.  And, or course, different transistors.