Parentheses Mini Fuzz - No LEDS or Fuzz Signal.

[Linkinbassist]

Hey there,

It's been a while since I've built anything but thought I'd grab something to do while I'm at home so bought a Pedalpcb Parentheses Mini Fuzz to put together. Finished it a couple nights ago and it has some major issues that I can't debug on my own. The boost works and passes signal, but the rat side seems to shunt everything to ground - when engaged, nothing passes. I get a hissing or a buzzing depending on how much the pots are engaged. Neither of the LEDS work either, though I put those in backwards initially so they may be blown. The readings are as follows:

Q1
1- 9.12
2- 0.28
3- 0.00

Q2-
1- 3.90
2- 2.36
3- 9.12

Q3
1- 2.43
2- 1.75
3- 2.42

Q4
1- 9.12
2- 0.31
3- 0.00

Q5 (boost)
1- 4.65
2- 2.24
3- 0.19

IC
1- 8.90
2- 4.56
3- 2.26
4- 0.00
5- 0.00
6- 4.56
7- 9.12
8- 9.01

The Germanium diodes have flow at the ends I can get to. Of the pots, only The distortion sees any current flow and that depends on how far it is through the sweep. The Octave sees less than .4 on any log and the filter/amplitude see nothing. Please help as I'm testing my hair out slightly 

Thanks in advance!

EDIT: Pictures to follow but let me know what, if anything, you want or need to see!

[Linkinbassist]

Picture of the top of the board, apologies for the size:

[Linkinbassist]

Solder side of the board:

https://imgur.com/gallery/AboYZD3

[bluebunny]

Picture of the top of the board, apologies for the size:

[IMG HEIGHT=nnn] ... [/IMG]

("WIDTH=" works too.)

[DIY Bass]

First thing I notice is that on the component view, all the holes have a small bit of solder coming up to the top side of the board, except one side of the ceramic cap at the bottom left.  I couldn't really see from the solder side photos what that joint looks like on the solder side, but it is worth double checking.

[Linkinbassist]

First thing I notice is that on the component view, all the holes have a small bit of solder coming up to the top side of the board, except one side of the ceramic cap at the bottom left.  I couldn't really see from the solder side photos what that joint looks like on the solder side, but it is worth double checking.

Tha is for the reply  I've reflowed the joints on both ceramic caps and still nothing. Could it be a dodgy 3PDT switch? The in/out labels aren't on the board, which doesn't help...

EDIT: It's not the switch. Continuity testing shows it's fully functional.

[iainpunk]

the voltage at pin 3 of the opamp seems quite low, ideally it should be the same as pin 2 and 6, maybe look at that. its odd that the output bias is correct tho....

i hope this helped somewhat

iain

edit, the glass germanium diodes look like they are the wrong way around? if you look at the build doc, versus your picture, the band seems to be on the other side from the drawing

do you have an audio probe, maybe check how far the signal goes before turning to static/silence

[Linkinbassist]

the voltage at pin 3 of the opamp seems quite low, ideally it should be the same as pin 2 and 6, maybe look at that. its odd that the output bias is correct tho....

i hope this helped somewhat

iain

edit, the glass germanium diodes look like they are the wrong way around? if you look at the build doc, versus your picture, the band seems to be on the other side from the drawing

do you have an audio probe, maybe check how far the signal goes before turning to static/silence

Thanks, it kinda does I think. The diodes are Russian D9E diodes and i've been advised that the band sits opposite to the board. Current flows through them, so that would suggest this is correct.

Looking at the schematic it would appear that IC pin 3 collects the signal from the first part of the circuit which comes through the Octave pot, so the problem is most likely there or before there, however when I trace the signal, there just...isn't one? I'm using a Multimeter as I don't have an audio probe, so I may be using the wrong setting and also I'm still trying understand how to read schematics/follow and trace signals. The 3PDT switch is fine, I tested that earlier. Power gets to the first leg of Q1 but neither legs 2 or 3 give off a reading. The circuit seems to be dead on that main rail between the circuit input and pin 3 of the IC. The Distortion pot gives a reading but it's off to the side of the schematic/IC so that would make sense. Everything looks in place but it only produces varying degrees of white noise depending on how your turn the pots

[PRR]

> the voltage at pin 3 of the opamp seems quite low, ideally it should be the same as pin 2 and 6, maybe look at that. its odd that the output bias is correct tho....

What is the voltage of a 1Meg source when loaded with a meter, say 1Meg?

[Linkinbassist]

> the voltage at pin 3 of the opamp seems quite low, ideally it should be the same as pin 2 and 6, maybe look at that. its odd that the output bias is correct tho....

What is the voltage of a 1Meg source when loaded with a meter, say 1Meg?

If i told you it came up as zero, you'd probably assume I'd done something wrong 

Seemed that no matter what pin I touched, I got no reading from those points. I'll repeat the test in the morning to make sure...

[Rob Strand]

If i told you it came up as zero, you'd probably assume I'd done something wrong

Looks like something is wrong.

Before you got these readings.   

IC
1- 8.90
2- 4.56
3- 2.26
4- 0.00
5- 0.00
6- 4.56
7- 9.12
8- 9.01

The voltages on Pins 2 and 6 imply the opamp itself is working fine.   The voltage on pin 3 should also be 4.56V but the meter loading would drop that to 4.56/2 = 2.28V (with a 1M input impedance meter).

That being the case you should at least get unity gain through the opamp.   Like you still could have a problem with the Drive pot wiring, or the caps to ground aren't connecting.   But even with those faults the opamp should pass signal.

[iainpunk]

please just put together a simple audio probe, its my favourite tool to use when something is broken, you can just use one of those "mini amps".

the schematic for an audio probe is simple, if you have a spare 1/4" jack, a big cap (100nf or bigger, not polarised) and a big resistor (2M2 or bigger)

[Linkinbassist]

please just put together a simple audio probe, its my favourite tool to use when something is broken, you can just use one of those "mini amps".

the schematic for an audio probe is simple, if you have a spare 1/4" jack, a big cap (100nf or bigger, not polarised) and a big resistor (2M2 or bigger)

Thanks, I did exactly this and followed the audio. It comes in, goes up into leg 3 of Q1 and just...never leaves. I've tried jumpers, hard soldered the Transistor to make this possible, but still nothing. Audio just never gets past the Transistor. Following the circuit, it looks like legs 2 and 3 are supposed to run into each other or follow the same track? But I can't see where the middle leg goes on the circuit at all. Properly stumped now 

[Slowpoke101]

You may have Q1 installed backwards (even though the documentation may say otherwise ). Since you have the transistor in a socket, take it out, rotate it and reinstall.
See what happens to the audio after doing that.

[Linkinbassist]

You may have Q1 installed backwards (even though the documentation may say otherwise ). Since you have the transistor in a socket, take it out, rotate it and reinstall.
See what happens to the audio after doing that.

Just tried that. The signal now goes down the middle leg but nowhere after that. Nothing through C3 or C10, even with jumpers, so nothing through the octave or the rest of the circuit...

[Slowpoke101]

Is the signal getting through C2 and then Q1. If it is you should hear a signal (audio probe ) on one leg of R4?

A couple of more questions. What are the voltages now on Q1 and Q4? Also, how tightly do the sockets you used for the transistors hold them? Are they loose?

[Linkinbassist]

Is the signal getting through C2 and then Q1. If it is you should hear a signal (audio probe ) on one leg of R4?

A couple of more questions. What are the voltages now on Q1 and Q4? Also, how tightly do the sockets you used for the transistors hold them? Are they loose?

Yes to C2 and Q1, yet no audio on R4. Voltages are still 9.12v or there abouts. The sockets are tight.

[Slowpoke101]

OK..Next questions. What type of transistors are you using for Q2, 3 & 4 ? Also the JFETs Q1 and Q5?
Not worried about Q6 at the moment.

After a bit more thought Q1 may have a broken circuit board copper trace than connects to its middle pin. Check the following image and do a continuity test (or low Ohms test ) with your multimeter between the points marked with arrows. There should be continuity between all those points. The larger arrow points to Q1's centre pin. Make sure that the effect is not powered during this test.

[Linkinbassist]

OK..Next questions. What type of transistors are you using for Q2, 3 & 4 ? Also the JFETs Q1 and Q5?
Not worried about Q6 at the moment.

After a bit more thought Q1 may have a broken circuit board copper trace than connects to its middle pin. Check the following image and do a continuity test (or low Ohms test ) with your multimeter between the points marked with arrows. There should be continuity between all those points. The larger arrow points to Q1's centre pin. Make sure that the effect is not powered during this test.



Thanks for the guidance  So no continuity at any of these points, however it also looks like the film cap at C2 doesn't have any continuity. I think I'll need to replace it before going any further. Gonna order a bunch of spares in the interim. Continuity gets to that cap and then no further...

[Slowpoke101]

No continuity at all ? Anywhere between any of the points shown ? Oh dear....
First rule when a test fails - test the test gear - when you short the test probes together (continuity mode ) does the meter make a noise ? If it does good, if it doesn't then find out why....
Assuming that the meter is fine, can you clean the solder side of the board ? Remove some of the flux residue so it's a bit easier to see if there is any damage to the copper tracks. Once that's done could you take another picture and post it here please.
A most suitable cleaning tool is an old toothbrush. Suitable chemicals (I don't know where on the planet you are so I'll list a few different types ) - Methylated Spirits, Denatured Alcohol, Shellite, Naptha. Acetone can be used but very sparingly and preferably outside.

Note if you are getting some audio up to Q1 then C2 is fine. A capacitor does not normally show continuity unless it's faulty or it is a large value capacitor that is charging via the continuity tester - once the capacitor is charged enough it will now show as open circuit to a continuity tester.