Big muff hum sound problem

[Pokrzi]

Hello guys, I'll try to be as clear as I can be.

It's my first DIY kit that I bought few days ago. I used manual, which was gave to me after purchase. Here are photos:



And these are photos of the PCB and all the connections:




What's the problem? I have what I believe it's called "hum sound". I have no idea what went wrong with this thing. Here's what I've checked:

Voltage with multimeter. (It's 9V)
Every connection on PCB (Continuity mode)

I hear that all of three knobs are working. Tone and volume of hum changes.

I believed I messed up 3DPT thing.

I hope You can help me figured it out! Thanks in advance!

[PRR]

Welcome.

Is there a metal box?

A high-gain audio circuit in a room with wall power outlets tends to pick up ALL the hum in the room.

[jfrabat]

Chasing the same issue here: https://www.diystompboxes.com/smfforum/index.php?topic=122693.0

Have not yet tried the last suggestion...

[Pokrzi]

Welcome.

Is there a metal box?

A high-gain audio circuit in a room with wall power outlets tends to pick up ALL the hum in the room.

Hi, unfortunately I didn't buy a box for this one, I thought that it will be at least sounding fuzz-a-like..

[SPoT_D]

Is there any of the guitar signal coming through?
Or is it just the hum?

[Pokrzi]

Is there any of the guitar signal coming through?
Or is it just the hum?

With effect off - guitar signal goes well
Without - not really, I think it's only hum.. even when I volume down guitar with knob and trying pluck strings - no output

[SPoT_D]

Hmm.. It's hard to see on the pictures, but I don't see a problem with the 3pdt and if you don't hear your guitar do anything with the effect on, it probably doesn't have anything to do with the lack of a metal box..

Maybe you could measure the voltage at the transistors?

I think you can use GGGs document as a reference : http://www.generalguitargadgets.com/pdf/ggg_bmp_instruct.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

[Pokrzi]

Hmm.. It's hard to see on the pictures, but I don't see a problem with the 3pdt and if you don't hear your guitar do anything with the effect on, it probably doesn't have anything to do with the lack of a metal box..

Maybe you could measure the voltage at the transistors?

I think you can use GGGs document as a reference : http://www.generalguitargadgets.com/pdf/ggg_bmp_instruct.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a

Hi, thank You for Your response! I'm going to measure voltages this evening, so probably I'll post about this later this day,

[pinkjimiphoton]

sounds to me like a smoked electro somewhere in the audio path. do a search for audio probe, then work your way thru the circuit.

we always need voltages to be able to try and help.

[willienillie]

It looks like you have soldered to the rivets on the pots, so one or more is probably ruined.

[Pokrzi]

sounds to me like a smoked electro somewhere in the audio path. do a search for audio probe, then work your way thru the circuit.

we always need voltages to be able to try and help.

These are my voltages (according to PCB layout I attachted in first post):

Q1
Collector - Emitter 3,84V
Base - Emitter 0,57V
Base - Collector 2,26V

Q2
Collector - Emitter 3,86V
Base - Emitter 0,58V
Base - Collector 2,26V

Q3
Collector - Emitter 4,60V
Base - Emitter 0,36V
Base - Collector 2,19V/b]

Q4
Collector - Emitter 2,89V
Base - Emitter 0,59V
Base - Collector 1,82V

Voltages between positive from 9V and every C,B,E pin are the same like in the instruction above.
Except for one transistor from jfrabat's instruction which was Q4:
Q4 Collector 4.0
Base 2.5
Emitter 1.8

Mine are
Collector 3,7
Base 1,7
Emitter 1,2

[Pokrzi]

Here's video:

https://www.youtube.com/watch?v=OKT4-ZZqb_Y

[duck_arse]

generally, we just connect the black meter probe to the ground, say the input jack sleeve, and leave it there. then we poke about with the red probe, and all our voltages are then referred to ground. anyhoo, the base to emitter voltage difference should be around 0V6, which your Q's 1,2 & 4 seems to indicate. but the Q3 base voltage is .... not. check the two base resistors are the correct values, and that thay connect, one to +9V/supply, and the other to ground/0V.

and if you could remeasure your transistor voltages, ground referenced, and post them again [as C, B, E], that would be nice.

I can barely make out your resistor colours, and can't make out anything on the circuit diagram, but, perhaps look very closely at the colour bands on R4 and R15, which both should be black-green-black-brown-brown black-green-black-red-brown.

[edit :] I am an idiot. red multiplier, not brown.

[Pokrzi]

generally, we just connect the black meter probe to the ground, say the input jack sleeve, and leave it there. then we poke about with the red probe, and all our voltages are then referred to ground. anyhoo, the base to emitter voltage difference should be around 0V6, which your Q's 1,2 & 4 seems to indicate. but the Q3 base voltage is .... not. check the two base resistors are the correct values, and that thay connect, one to +9V/supply, and the other to ground/0V.

and if you could remeasure your transistor voltages, ground referenced, and post them again [as C, B, E], that would be nice.

I can barely make out your resistor colours, and can't make out anything on the circuit diagram, but, perhaps look very closely at the colour bands on R4 and R15, which both should be black-green-black-brown-brown.

Hello, checked voltages using your method.

Q1

C - 3,89
B - 0,61
E - 0,01

Q2

C - 3,90
B - 0,62
E - 0,03

Q3

C - 3,80
B - 0,62
E - 0,02

Q4

C - 3,80
B - 1,60
E - 1,13

I'm checking resistors right now

R4 and R15 are both 15kOhm so it's seems to be fine

[Pokrzi]

Better look here:

[duck_arse]

well, your transistor voltages now look OK/good/right/as expected. I think you have a wiring problem. the best way to yes/no this is to remove all the stuff hanging off the board, connect signal [and ground] to the input, connect V+ and 0V, and monitor the output at C13 (-) leg. which will be at full volume. you will also need to connect C3 to C4 to get signal through, and connect C12 to the junction of C9 and C10. if you get loud out, you're getting somewhere.

you also need to rewire those pots without using the rivets as solder eyelets, as willie mentioned. and work on your wire dress at the board, so there are no spider's legs or wire hairs going stray and shorting across. a lighter gauge of wire might help, strip the insulation and twist the bare strands, then tin them w/ solder before poking into the board and soldering.

[Pokrzi]

well, your transistor voltages now look OK/good/right/as expected. I think you have a wiring problem. the best way to yes/no this is to remove all the stuff hanging off the board, connect signal [and ground] to the input, connect V+ and 0V, and monitor the output at C13 (-) leg. which will be at full volume. you will also need to connect C3 to C4 to get signal through, and connect C12 to the junction of C9 and C10. if you get loud out, you're getting somewhere.

you also need to rewire those pots without using the rivets as solder eyelets, as willie mentioned. and work on your wire dress at the board, so there are no spider's legs or wire hairs going stray and shorting across. a lighter gauge of wire might help, strip the insulation and twist the bare strands, then tin them w/ solder before poking into the board and soldering.

I didn't try this C13 and so on method, I rewired whole thing and still nothing changed. I'm kinda giving up

[Pokrzi]

Hello again Everyone!

After some time I've tried to make things work once again and.. I've found the solution! |

3PDT Switch was faulty! I figured it out by making simple audio probe and checking first of nine pins in switch!

Thanks for helping, hope You find this thread helpful. Sometimes we look for mistakes too deep.

[duck_arse]

nice work. what's next on your list?

[Marcos - Munky]

3PDT Switch was faulty! I figured it out by making simple audio probe and checking first of nine pins in switch!

Nice you got it to work! It's always a nice idea to test circuits before adding the switch. This way, you will know the problem is not related to the switch if the board doesn't work, because there's no switch at all. And most important, if the board was working and then it's not anymore after you added the switch, you'll look for the problem directly on the switch part and won't waste time searching anywhere else. Also, the audio probe is your best friend for debugging a lot of circuits.

Sometimes we look for mistakes too deep.

Ha! Write this quote somewhere, and then read it again when you spend hours trying to figure out why a circuit is not working, when you actually forgot to plug in the power supply or the cable to your guitar. Yep, almost all of us already did those things, and who didn't made those "mistakes" yet will surely do them some time in the future