Build Your Own Clone Message Board

+1 on the audio signal probe. The direct signal path for this pedal is quite simple - into and out of a unity gain input buffer (T1), through the gain control divider formed by R3 22K and T6, out of the junction of R3/T6 to the input of the unity gain output buffer (T2). Using the probe check for signal on the base and then the emitter of T1 (signal must first pas through the input jack and the foot switch). Then on the base and emitter of T2. Once the signal reaches the emitter of T2 it passes through the foot switch and out through the output jack.

The swell effect is controlled by a side chain - the input signal is greatly amplified by the IC UA741 and drives an envelope follower consisting of T3, T4 and T5 and the capacitor C9 0.68uF.
The envelope follower produces a control voltage that follows the attack and decay of the input note. The control voltage drives the gain control through the JFET T6 2N5457.

While there is no input the control voltage on the gate of the JFET is high, the JFET is turned on and it shunts signal to ground. When a note is played into the input the capacitor C9 is discharged through the attack pot, the voltage on the JFET gate falls, the JFET turns off and signal passes between the input and output buffers.

This means that if the op-amp and the envelope follower aren't working and the capacitor C9 is not ever discharged through the attack pot the JFET remains on all the time and the pedal won't pass any signal. A quick method to diagnose problems with the side chain is to apply a temporary short across C9 0.68uF. If you then hear the pedal passing signal you know the direct audio path is OK and that the JFET is working. Your problem therefore lies with the side chain - the op-amp, T3,4 & 5 and associated connections and parts.

If you have a multimeter and know how to use it here are the ideal voltages (actual voltages may vary by as much as 0.5V) you should see on the transistors. If you do not know the lead-outs for the transistors search the web for data sheets -

T1
C = 9 (supply voltage)
B = 4.22
E = 3.59

T2
C = 9 (supply voltage)
B = 3.55
E = 2.93

T3
C = 5.99
B = 3.66
E = 3.01

T4 & 5
C = 5.59 (should be the same, they should be connected together)
B = 1.40
E = 1.40 (should be the same, they should be connected together)

Pin 6 of the UA741 should be at Vref = 4.47 (Vref is from the junction of R15 and R16)

The stripe end of the Zener diode D4 should be at 5.6V

Sweet! Thanks! At least this info, I have somewhere to start.

I'm looking at that schematic and let's just say I hope that .68 is the issue. That one I know where it is on my board. I don't know how to turn a schematic into a guitar pedal, lol.

Circuit schematics are actually very simple to read you know. Resistors are the zig-zag symbols, capacitors the two parallel lines, op-amps the triangles and transistors the vertical bar with the two diagonal lines. The lines between everything represent the connections, in the case of the circuit on a PCB they are the tracks.

The 0.68 uF capacitor is the only tantalum cap in the kit, it looks like a shiny yellow/beige blob. It's just above the edge pad labelled 'jack'. I can even see the white legend .68 in your pictures.

Just short out that cap, in this case a short across it will do no harm. One way to do this other than shorting directly across the cap connections it to connect the A1 tag of the attack pot to circuit ground (circuit ground is the sleeve of the input jack) with something like a miniature crocodile clip lead.

If you hear signal through the effect with that cap shorted then your problem lies in the side chain as described in my previous post.

I know what most of the symbols mean, but I would need to watch someone take a schematic and put it to a board.

I did that jumper across the .68 cap (soldered a wire on one leg and then the other end of the wire to the other leg). I think that is wat you meant. Absolutely nothing changed..... Not really sure if this is good or bad, but it almost feels like progress....

That means the fault is likely to be in the direct audio path - input jack - foot switch - R1,C1, base T1, out of emitter T1 - R3, C3, C4 - base T2, emitter T2, R9, C6 - foot switch - output jack.

If you could use a multimeter to check those voltages that would be good and then maybe use an audio probe to see if there is signal on the emitter of T1.

If it turns out that the input signal doesn't even get through the input buffer (T1 and associated components) then of course there is no effect output.

This is really going to suck because I know nothing more about volt meter than getting continuity. Almost everything you said was foreign... I've modded dozens of pedals and never once had an issue, so I figured I would try this.

And to make matters worse, I hit the radio shack for an audio probe and they don't have them and she didnt even know what one was.

Assuming you have a digital multimeter - set the range to 20V DC.
With the black lead plugged into the COM socket on the meter and the red lead into the Volt/Ohm socket connect the black probe to the circuit ground ( the sleeve of the input jack is ground ). Then use the red probe to touch to the points in the circuit to make your voltage measurements. Be very careful not to slip with the probe and short anything.

An audio probe can be made by from a jack lead. Strip one end of the lead and separate the ground and live. Wire a capacitor in series with the live and use the free end of the cap as your audio probe. Plug the jack end of the lead into an amp and connect the ground at the other end to the ground of the circuit you are testing.

The cap value is not very critical, something around 0.1uF will do.

I use my test rig, I just clip the alligator clip that goes to the out jack to a tiny screwdriver

_________________
Pedal building is like the opposite of sex. All the fun stuff happens before you get in the box.

Nope. Went cheap and got old school analog. I don't even know what a COM socket is. As I said, I only bought it for continuity. I didn't think I would ever use it for anything else. I appreciate your help, but I'm simply too ignorant in electronics to know what you are talking about. Maybe I should rip the whole thing apart and start over... but I don't know what good that would do as I tripple checked everything in the troubleshooting process. Crap! And I'm sitting here thinking about all the pedals I've modded with worse directions than what came with this. I simply don't understand. I have NEVER once had a problem with other pedals or wiring guitars or anything like that. I'm frustrated....

I can pretty much rule out the switch; jacks and power supply; correct?

Not without an audio probe.

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Pedal building is like the opposite of sex. All the fun stuff happens before you get in the box.

Ok. One thing I did in fact notice (I dont know if these are PNP or NPN) but the transistor that is to the right of the trimpot and to the left of the .68 cap, the leg on the right has no reading on my voltmeter when I put the black tester to a ground and the red on that leg. On every other transister, that leg reads something. Could this be the problem?

I cant follow those directions with the PCB oriented with all the wire connections at the bottom. I think you might mean Q6 which is the JFET.

See here for PCB layout

http://www.buildyourownclone.com/board/viewtopic.php?f=21&t=39390

I think I need to find someone who knows about pedals and have him deal with it. I think I have 6 hours of troubleshooting and seem to be getting nowhere. I really did not expect to run into this at all.

Ok I'll be the first to admit when I'm an idiot. Now's the time. I had the friggen jacks backwards. I thought stereo was out to amp. Once I corrected this, and switched it all, I now have sound when the pedal is on or off. But now I have another issue. I am not getting the swells that a slow gear is supposed to give. Any ideas?

Did you try dialing in the trim pot again?

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"It’s your soldering."

Yes. Nothing I seem do do changes anything EXCEPT when pedal is engaged, I get about 20% volume loss. Probably something stupid on my end like those stupid jacks.

It is working great except the swell. Everything else works perfectly now. Any ideas? Probably nothing simple. One thing I've learned is to quit being so cocky about my mods that I've done....

what kind of guitar are you using to test the pedal? I've noticed that my sprocket never liked high-output pups. basically, the hot signal seemed to overwhelm the swell. I couldn't get it to sound right until I switched to some lower output single coils. it's also a fairly subtle effect, unless you perform a mod I found here which makes the swell more dramatic.

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A Fender Strat with Vintage Noiseless pickups, a PRS Custom 24, and a Mexi Fender tele with Texas Specials. I didn't bother with any others.

Try this: sens at 9:00 o'clock attack full cw. Adjust the trim pot until you get swell. Pick one note at a time and damp the string before the next note for this adjustment.

Also, is the trim pot turning infinitely or does it stop at the lowest and highest points?

With high output pickups, try turning the volume on the guitar down. You can dial in a sweet swell that way!