Help with debugging (new schematic)

[Jussi]

Hey,

I have built this fuzz/od pedal and it worked well on breaboard but now the purple led starts glowing and no sound comes when I put the switch to position where it skips that OA7 diode. If i bypass the resistor, it will glow brighter

At the other position (OA7 goes to LED) it works fine. I checked with a flashlight inside my led to see where is the anode of it and it looks its placed right way.

Any guesses?

[gcme93]

Try another switch? Test out if it's a problem with the switch by creating a short from the orange wire on the vero, to the LED connection on the switch. It sounds like the only explanation really?

[Jussi]

When I short it it will start glowing so the switch is working

[gcme93]

Surely the switch doesn't work if the LED only lights when there's a short circuit across the switch? If the wiring is exactly the same as your diagram, that can be the only problem really. Especially if it works perfectly in the other position.

[Jussi]

Surely the switch doesn't work if the LED only lights when there's a short circuit across the switch? If the wiring is exactly the same as your diagram, that can be the only problem really. Especially if it works perfectly in the other position.

It does light but it shouldnt. The led is being used for a diode overdrive in this circuit and it never lighted on breadboard when the effect worked.

When the switch is at the position where it should skip OA7 it has a voltage of 3,69 at ALL pins of the switch and after led 0,69. Is it normal?

[gcme93]

I think the easiest thing to do here is to get a digital multimeter out and measure the resistance between the switch pins at the different setting. With the battery unplugged, the diode should act like an open circuit, so you can test whether the switch is working properly?

[Jussi]

I got a multimeter and i just checked it with 200 ohm setting. At one position the 1st pin had 0.08 resistance and at 2nd pin the meter just stayed at "1 .".  At other position 1st pin had "1 ." and 2nd pin "0.08" so i guess its working.

[gcme93]

That's me floored then :s anyone else got ideas?

[blue_tokai]

I hate to ask, but does your graphic representation match the schematic??
I looks like the input from the jack to the base of the transistor is wrong... compared to the schematic

[gcme93]

The thickness control is on the other side of the input caps from the schematic which doesn't make a difference, and the transistor on the layout picture is oriented back to front (the flat face should be pointing upwards)

If the transistor is the wrong way around, thats a nice quick fix, but it doesn't sound like that is the problem...

[Pyr0]

The graphic representation of your layout looks ok, except for how you have the switch wired. The orange wire from the transistor collector should go to one outside lug of the switch, and the diode should have it's anode also connected to the collector, with it's cathode on the other outer lug of the switch, then connect the anode of the LED to the center lug of the switch and it's cathode to the base.
Edit: or an easy fix would be to just swap the orange wire and the led on the switch and leave the diode as is.

[gcme93]

You're right about your suggestions Pyro, but I think you'll find what he has on the layout diagram has exactly the same effect if you follow the two paths created by either side of the switch. The only thing that the current configuration relies upon is that when switched to "no OA7" the OA7 acts as a perfect open circuit which actually I don't think it does.

I think your OA7 is either not suitable for this assumption (i.e follow Pyro's advice and the path more explicitly split between each side of the switch), OR maybe your OA7 is dead, especially if you are getting equal voltage across all pins with the switch across? It's just being a short circuit if so...

Ignore all the rubbish in pink. That shouldn't make any difference whatsoever, because if it's shorting, there's no circuit to flow through :/ follow Pyro's advice and make a more explicit break in the two paths?

[Jussi]

The transistor was wrong way in the layout and my build. I got confused by PNP/NPN stuff or something because I'm building a fuzz face at the same time. Thanks for the help!

Anyways, it sounds cool with guitar and bass. Gain is adjusted from your instrument's volume pot. With the OA7 germanium diode it sounds like it adds a quiet octave phaser distortion or something and is a lot more dynamic and thickness control works a little different.

I recorded a little bit with my cellphone and guitar (tried both p90 pickups and many settings settings) and blackstar ht-5r (very low volume, clean and od channel). http://soundcloud.com/666saatana/sounds-from-wednesday-4
What do you think?

[gcme93]

Nice bro!

I'm not really a high gain kinda guy but I really like the softer clipping at the beginning. Very nice smooth overfuzz (if thats a word)