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Hello all,
I just finished building the v3a MOWAH. As suggested in the build document, I socketed all of the transistors and the four capacitors. I was planning to just use a C100K pot so I could set (cock) the WAH so I could put it into a small enclosure and just turn it on and off.
When I tested it, I got the distortion promised by the caps and switches but NO wah. I have tried both a philips inductor and a Dunlop Faser and still there is no wah.
Any help will be GREATLY appreciated!
Alex
Does anyone have any suggestions for what I might try? Here are a couple of pictures of my build.
Hi, good morning!
I understand that this isn’t an autowah. I plan to put this into a standard 1590N1 enclosure and hand-set the wah. For trouble shooting, I removed the foot switch so at this point it is always on. There is no change in tone when I turn the pot except when I get to the center of the sweep where I notice a slight change in background ‘hiss’. I have tested the pot and I read 100 at both ends, so it’s fine.
I’ve rechecked all of my connections and part values. I have also tried two different inductors. A phillips 4 pin (first) and then a Dunlop Red Fasel. Neither made any difference. I have also adjusted both trimpots and the only impact is to volume.
I am fairly uneducated when it comes to electronics ( I understand the basics) but one thing that comes to mind is that perhaps the way I’ve connected the jacks and power may be a factor. As you’ll see in the attached picture, there is only one ground going the the circuit board. Could this be the problem?
Thanks for responding
No, I’m using J113 and 2n5088s from Barry. I’ve swapped them out for others (same parts) with no effect. TR1 is controlling volume but TR2 doesn’t seem to be doing anything.
According to the schematic, TR2 is the final volume output control. TR1 (with R9) should be controlling the “Q” factor of the sharpness & amplitude of the filter. (See page of the build document.) Lift one leg of R9 and see what changes. If you do that, TR1 should have zero effect (change) when turned.)
Finally, from where did you get the inductors? They need to be 500mH “wah” inductors to work properly. (Had to ask.) 😉
I had it backwards. TR1 wasn’t doing anything and TR2 was controlling volume. As you suggested, I disconnected R9 and when I tested, TR1 has no effect and TR2 is in fact still controlling volume.
With a guitar plugged in, the sound is quite trebly and harsh. SW1 does in fact add/remove some bass and SW1 has no effect.
The Red Fasel is from Dunlop. Purchased from Amazon. I don’t have the equipment to measure the mH, The Fasel came with no technical data but the web indicates that the Red Fasels should be between 500mH and 600mh.
The Fasel inductor is mounted incorrectly. One pin must be in on the white pad.
Thanks for jumping in Wilkie! I was getting stumped. I saw that in the build docs, but by the traces shown on the PCB, the white pad is also connected to the group of pads beneath it. N’cest pas?
I saw that too. Initially, I installed a Phillips 4 pin inductor and the only way it would line up with the mounting holes was to use the white pad. Because that didn’t work, I went to the Red Fasel. As the PCB groups two mounts inside a box, I used them. I also noted that the trace appears to connect the white pad to the pad directly below.
I will try relocating the Fasel and will let you know.
I saw that too. Initially, I installed a Phillips 4 pin inductor and the only way it would line up with the mounting holes was to use the white pad. Because that didn’t work, I went to the Red Fasel. As the PCB groups two mounts inside a box, I used them. I also noted that the trace appears to connect the white pad to the pad directly below.
I will try relocating the Fasel and will let you know.
Update: Nope. No difference. R9 was reconnected. TR1 still has no effect.
Have you measured the resistance of the inductor? It should have a measurable resistance reading. One leg of it will need to be lifted.
Alex – yes. The resistance value is not as important as the mH (inductance) value. The resistance measurement tells us that the inductor is not open.
Do you have an audio probe? If so, you’ll want to probe around the circuit and try to figure it out that way. If not, they’re dead-simple to make.
Thanks for the advice. I had to find out how to build a probe, which I did. Now I have to try and understand where to start probing! I’ll let you know! Thanks again.
okay. So I’ve been tracing the signal path from the input. I get as far as R7 which connects to one side of the fasel L1. I have signal at R4 and at one side of L1 I also get signal on one side of R7 but not the other and not at the R7 side of the fasel. As mentioned earlier, the fasel appears to be functional. All of my solders are good and clean. And as mentioned, I get output but no wah.
I’m once again stuck! I tested R7 and it’s fine. Why would I get signal on one side but not the other??
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