Parentheses mini fuzz: Distortion switch kills signal

[Maximiliaan]

Hello everyone,

So I built this kit I got from Musikding. Here are the schematics: https://docs.pedalpcb.com/project/ParenthesesMini.pdf

I didn't include the leds because it was too annoying to try to fit them in.

Also, my build has an OP07 instead of LM308 and two 2N5457's instead of PF5102's.

When I tested the pedal, the bypass worked fine and so did the booster/octave. However, when I activate the distortion, things don't work anymore. The signal just seems to die unless I switch the booster knob and the volume of my guitar all the way up. Then I get some almost decent sounding fuzz but it remains extremely quiet.

What could be causing this? Could it be a bad IC or transistor? I think the wiring and soldering are ok. I checked the connections as I was building and everything is oriented correctly.

Any advice would be greatly appreciated.

[bartimaeus]

"bad" components are very rarely the cause of problems, unless you solder them for too long and they burn up.

if all components are correct, then most likely it is a problem with your wiring or your soldering traces.

it is hard to say about the soldering, because your first photo is very blurry. can you upload another?

though i notice the soldering on one pin of one of the pots is not covering the whole pad, that could be part of the issue.

EDIT: also, i notice you chose not to include the ground connection or the jumper to the center bottom pin of the footswitches. that won't break your pedal, but it does mean the input of each effect section is left floating. this can cause noise issues like oscillations. even if you leave out the LED, you should include those wires, and just remove the red wire.

[Maximiliaan]

I hope this one is better. I don't have the greatest phone so it's hard to make super clear pictures.

I will do the suggestions you gave and see if it changes anything. Thanks for the advice!

[eh la bas ma]

Hello, welcome !

I can see a few suspicious solder joints on your board.


Don't forget to take every heat-sensitive components out of the board (transistors and IC), before reflowing your pads.

[GibsonGM]

^  This, yes.   And when you're building, you can use a heat sink to protect things like transistor legs as you solder them in.

Like this:  https://www.jameco.com/z/HT-156-Jameco-ValuePro-Clip-On-Heat-Sink-for-Soldering-Sensitive-Devices_159126.html

[anotherjim]

That's a heavy-handed way to switch the clipping diodes. Might have well been one pair of 1N4148 with the LED in series with one and the switch just shorts the LED for the diode-only position. I suppose it gives extra options for diode types the way it is... but unless you fit sockets you're going to wreck the PCB vias in short time if you do substitions.

The here project displays one of my current pet hates. The PCB. It may technically be an excellent board, but why do we have to have those skinny traces at the expense of massive ground pours and unnecessarily tight clearances? Soldering to the ground takes a lot more time & heat with the potential for damage/incomplete joints. If you make a mistake, rework has an increased chance of causing damage.

Anyway, rant over. I can stick to perfboard.

And the DMM continuity "beep" test is your friend. If you think something "might" be touching something it shouldn't, see if it beeps. If it don't beep, it ain't touching.

[Maximiliaan]

Ok, I will reflow the joints that look bad and see if that helps.
Unfortunately I have a lot of work this weekend so I will get back Monday probably.

One more question. Is the orientation of the switch important in this circuit? It seemed to me that it wasn't so I just put it in randomly. I may have been mistaken though.

[eh la bas ma]

One more question. Is the orientation of the switch important in this circuit? It seemed to me that it wasn't so I just put it in randomly. I may have been mistaken though.

No it doesn't matter. You'll be able to hear the clipping diodes change with the toggle, once the circuit will work. Sometime it does matter, the instructions usually mention it.

I would bet on a short or a bad solder joint somewhere, maybe more than one. Don't forget AnotherJim's suggestion to use a multimeter. Continuity tests will tell you if there is something wrong or not. Follow schematics to see if 2 pads should be connected or not. Power supply unplugged (or it might confuse the results).

If it was my build :

1/ with a desoldering pump, remove solder on the pads with too much solder. An old toothbrush will be helpful to clean the board.

2/ add some solder on a few pads where there isn't enough, iron set around 400°C.

3/ try to clean the tiny spaces between pads, going quickly with the iron.

4/ check the wiring carefully. We often do silly mistakes here, and realize later that it was a simple confusion.

5/ if it still doesn't work, I would start the hunt for shorts with a digital multimeter (DMM) on continuity mode.

6/ Finally, if it still doesn't work then, I'd start to check all connections with the DMM on continuity mode, following schematics. Making sure every component is correctly soldered and connected to the next component as it should.

7/ if nothing works, i would turn to the DIY goddess, make a sacrifice or something (probably should have done it sooner), and go with the audio probe. Following the signal path on schematics and on the board, to see where is the issue. Note that you can use the audio probe much sooner in the debugging process. I just don't like audio probing very much, but sometimes... It is a great tool to troubleshoot a circuit :

http://diy-fever.com/misc/audio-probe/

[duck_arse]

Maximiliaan - voltages. always, ALWAYS - the voltages, then the questions. and the welcomes.

please post your voltages, especially for the two jfets and the opamp pins. there are many a people build rat-or-alikes and complain about levels until they rebias the jfets to half Vcc with a second resistor. but your voltages may very well instruct us.

[Maximiliaan]

Apologies for not posting the voltages immediately. Here they are:

Q1(2N5457): D: 8,74V; S: 0,98V; G: 0,00V

Q2(2N5089): E: 3,69V; B: 2,34V; C: 8,74V

Q3(2N5087): E: 7,13V; B: 6,39V; C: 1,60V

Q4(2N5089): E: 0,22V; B: 0,75V; C: 6,38V

Q5(2N5457): D: 8,74V; S: 0,92V; G: 0,00V

Q6(BS170): D: 4,65V; G: 2,26V; S: 0,18V

IC(OP07): 1: 8,6V; 2: 7,55V; 3: 7,40V; 4: 7,95V; 5: 8,61V; 6: 8,74V; 7: 8,12V; 8: 0,00V

The DC voltage from the adapter was 8,97V.

[Maximiliaan]

Hey everyone,

I have discovered my mistake now and it is truly embarrassing. Pin 4 of the IC was not in the socket but sticking out. Because the parts are so close together I didn't notice it until now.

Now the pedal is working just fine.

Thanks for all the replies and the soldering advice!

PS: I also added the wires on the switches as Bartimaeus suggested.

[duck_arse]

some of your posted voltages are a bit screwy. now the unit works, would you be so kind as to remeasure and repost them?

[antonis]

Actually, the weirdest voltages are those of Q2..
(the buffer for octave effect..)

[Maximiliaan]

I did the measurements and for the transistors nothing really changed. The only significant changes were:

Q2: Base is now 2,25V instead of 2,34V (E: 3,69V; C: 8,74V)

Q6: Gate is now 2,02V instead of 2,26V (D: 4,65V; S: 0,18V)

The IC changed a lot. New measurements are:
1: 8,57V; 2: 4,37V; 3: 2,16; 4: 0,00V; 5: 8,56V; 6: 8,76; 7: 4,37V; 8: 0,00V

So I'm guessing there is still a problem with Q2. What should the voltages be and what could be causing the problem? When I test it, the booster seems to be working fine and the overall distortion+booster+octave sound absolutely killer.

[antonis]

For a happy n-p-n- BJT, Base voltage should stay about 600mV (more or less) higher than its Emitter voltage..
(the opposite stands for p-n-p, of course..)

edit: On a second thought, something goes wrong with the schematic..
Either D2/D3 should be flipped 180^o or Q2 should be p-n-p..
(or too later here in conjunction with too much beer..)

[Maximiliaan]

So now my pedal suddenly decided to stop working again. I completely don't understand anything anymore.

It is now the same as when I started this topic. Bypass and booster work fine but as soon as I switch on the distortion switch, no signal gets through. It is so strange because it was working perfectly and suddenly it doesn't work at all, even though I changed nothing.

Is it possible that something went wrong and one of the components was destroyed? I really don't know much about electronics so I have no clue what happened. How can a working pedal just stop working after a day?

I checked the voltages again and they haven't changed. I checked the wiring using a DMM, checked the connections between compenents and everything seems to be fine.

[duck_arse]

here's something, not it, but something. your diodes D2 and D3 - the linked docs show the board overlay with the Kathodes down. your board silkscreen shows those Kathodes pointing up. here's the rub; your diodes are "russian" types, marked band on the Anode. peer in the glass and you can see the square of germanium, usually denoting the Kathode lead.

so although your diodes are/appear fitted backwards, they DO agree with the silkscreen, which DOESN'T agree with the docs. as for the actual circuit and how it is connecting, you will need the pedalpcb people to tell, or use your meter to probe the connections.

this won't help your problem with the IC section, I don't think. maybe. also - this:

[antonis]

I still think that particular D2/C3 and Q2 configuration  can't work..
(unless it counts on very leaky Ge diodes..)

[Maximiliaan]

I was also confused about the diodes D2 and D3. I was aware that they are Russian and had the anode marked instead of the cathode. I just connected them like on the scematics, with the anodes linked to Q2. Maybe they should be reversed but since the pedal actually worked for a while, I don't think this can be the problem.

What do you mean with this picture of the IC and red arrow? Should I flip it? Because that doesn't really make sense to me.

Does anyone have any other suggestions? If not, I guess I'll just give up on this one and try another.

[duck_arse]

the pin numbering of all IC's is counterclockwise from left of the index notch, notch to top. your voltages suggest you have measured and listed left side top to bottom followed by right side top to bottom. so your listed pin 8 voltage was really your pin 5 voltage.

there is never a reason to rotate an iC, because you have made so many checks before inserting it that IT MUST be the correct orientation the first time. datasheets, for a reason.