SOLVED Pharmacist pedal lights no effect

[johnzero0]

Hi guys

I wonder if you can help, i just built a pharmacist pedal and after painstakingly ordering the individual components im getting lights but an almost inaudible low volume output with pedal engaged. pass through is working fine.

 

[johnzero0]

Thanks for sticking with it eh la bas ma
In green is the leg 1 of Q4 i am not getting sound, this is a new board using same BOM

Q5
1 16.9
2 16.9
3 2.6

 

[eh là bas ma]

I can spot a few suspicious pads. See reply #2. Green for those in need of reflowing, you dont want any bubble-shaped solder joint (Edit : I think Iforgot a few of them). Red for a possible short. Blue for remaining bits of leg (invitations for short). Purple for remaining bits of solder that can easily create a short, you can use a dry toothbrush, or move your iron quickly (no overheating the board) if they are stuck on the board.

Q4 Gate (pin 3) at 0 V is a bit surprising... Can you give your readings at C15 ? There should be a signal here, so 0V is suspicious. Check if you have continuity with ground at Q4 pin 3, that would indicate a short to ground, explaining the 0V reading.

Be that as it may, something tells me that it's probably a short or a bad soldering joint... Spending some time working on the pads should help a lot, and maybe even fix everything. See reply #2.

Here is an exemple of how it should look like, with all humility : clean, elegant, with a relaxing feeling of freshness.

 

[johnzero0]

Thanks again for the tips eh la bas ma, Im leaving some legs long as i may need to pull the components, i have found short legs hard to put in another board but if we can get this working i will take your advice on those. That board is great you'll have to tell me which iron you use.

let me include a diagram as i have seen in a similar post here so we dont have confusion around the number / pin / leg. i also traced back the 0v past C15 which reads 0v and 0v it goes all way back to the P1 which I'm not sure which component that is.

Edit please see diagram attached of my readings

 

[eh là bas ma]

So you do have audio signal, but it's all at 0V ? Is your multimeter set on DC voltage ? Does it have some auto-range feature ?

I guess if there is a good audio signal, it should be ok... You should probably focus on the soldering side.

P1, P2, P3 are the boost footswitch pads I think. Do you have the same readings, 0V at Q4 pin 3, if you try to press the boost switch on and off ?

I am using this soldering station, running at 400°C, from a local store :

Station de soudage numérique NEDIS - RER Electronic

Station de soudage numérique NEDIS Station de soudage digitale 48W SL30.

rer-electronic.fr

A bad soldering iron will certainly be harder to handle, but I think practice is also very important to improve our soldering skills. At first, I did some mistakes too, with the same iron. A fine iron tip is helpful too. If the tip is too big it will be much harder.

Edit : I know Hakko is among the best soldering tools brands.
About multimeters, I have been told to get a VC97A model, it's cheap and it's perfect. It can read Hz, which is useful with modulation circuits.

 

[johnzero0]

So im getting 0.01 on Q4 first pin from the left i am calling pin 3 at c15 i get 0.03 one leg 0.01 the other leg

Edit: the reading at q4 pin 3 does not change with footswitch of boost pressed

 

[steviejr92]

Those voltages certainly seem to be off. What does Q5 read?

EDIT: Just seen your post on Q5 that looks fine. Something is definitely wrong with Q4. Are you getting continuity between C15 and Q4 Gate?

 

[johnzero0]

Those voltages certainly seem to be off. What does Q5 read?

Thanks for looking Steviejr92

Q5
1 16.9
2 16.9
3 2.6

 

[eh là bas ma]

Those voltages certainly seem to be off. What does Q5 read?

see replies #61 and #63

 

[steviejr92]

see replies #61 and #63

Thanks for looking Steviejr92

Q5
1 16.9
2 16.9
3 2.6

Edited my response above

 

[johnzero0]

I have continuity between these 2 points in green

 

[eh là bas ma]

@steviejr92 : reply #63

i also traced back the 0v past C15 which reads 0v and 0v it goes all way back to the P1 which I'm not sure which component that is.

Do you think 0V on the signal path is ok ? There is audio signal from the audio probing test, but it reads 0V...

 

[johnzero0]

@steviejr92 : reply #63

Do you think 0V on the signal path is ok ? There is audio signal from the audio probing test, but it reads 0V...

Please see post #65 there is some voltage just above 0v

 

[steviejr92]

Have you tried reflowing C15?

 

[eh là bas ma]

there is some voltage just above 0v

I still wonder... 0.01mV could come from the multimeter probe... I wouldn't be surprised if I tested a ground point on a working circuit, and read 0.03 mV. I would think it's the DMM voltage reading impulse. I think 0V or 0.01 mV is the same thing...

 

[johnzero0]

Have you tried reflowing C15?

Have tried, the 0v goes back to r24 and i believe P1 but not sure where i can take a voltage reading of this component

 

[steviejr92]

I still wonder... 0.01mV could come from the multimeter probe... I wouldn't be surprised if I tested a ground point on a working circuit, and read 0.03 mV. I would think it's the DMM voltage reading impulse. I think 0V or 0.01 mV is the same thing...

Do you think since the pull down resistor is there, that explains the 0V hitting Q4 gate.

 

[steviejr92]

Have tried, the 0v goes back to r24 and i believe P1 but not sure where i can take a voltage reading of this component

R24 might be your issue. I would reflow R24 and see if that fixes anything.

 

[johnzero0]

I still wonder... 0.01mV could come from the multimeter probe... I wouldn't be surprised if I tested a ground point on a working circuit, and read 0.03 mV. I would think it's the DMM voltage reading impulse. I think 0V or 0.01 mV is the same thing...

You believe a possible short to ground somewhere? would audio still travel along?

 

[johnzero0]

R24 might be your issue. I would reflow R24 and see if that fixes anything.

Reflowed, same readings also no change to the sound the vol pot doesnt seem to affect the sound also not sure i mentioned it earlier.

 

[steviejr92]

I still want to say there’s a bad solder joint somewhere.

We might be going in circles with this one but it can’t hurt to try. Do you get continuity between C17 and Q4 source (1st pin of Q4)?