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.

 

[eh là bas ma]

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

I don't think so, that's why i wanted to confirm. In my experience 0V, or 0.01mV means ground... but there is audio...

Edit : Audio probe doesn't lie, if you hear the signal as loud as expected, it should be allright.

You should focus on the soldering, on your picture there was several suspicious pads around Q4. Remember : clean dome-shaped solder joints, elegant, like a breath of fresh air...

I gave you soldering tips in reply #2.

 

[johnzero0]

I don't think so, that's why i wanted to confirm. In my experience 0V, or 0.01mV means ground... but there is audio...

Edit : Audio probe doesn't lie, if you hear the signal as loud as expected, it should be allright.

You should focus on the soldering, on your picture there was several suspicious pads around Q4. Remember : clean dome-shaped solder joints, elegant, like a breath of fresh air...

I gave you soldering tips in reply #2.

Thanks again for the advice i will do as i did on the first board and reflow, however i may be the only pupil but im in the school of thought that it is a component most possibly incorrect value i chose
as this is the 2nd board with same exact fault and similar readings

 

[johnzero0]

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)?

Continuity from Q4 to C17 Again circled in green

 

[eh là bas ma]

a component most possibly incorrect value i chose

I gave you a link for Atlence resistor viewer. If you don't want to use it, I would suggest to desolder every resistors in this last section of the circuit and check their value with your DMM. This should have been done before populating the board, for every part.

 

[steviejr92]

Hmmm. I would reflow the entire board.

I see you might not know if you put a wrong value in the circuit somewhere.

Double checking all your values can lead you to the culprit. Good luck!

 

[johnzero0]

Thanks eh la bas ma, i have been focusing on the areas that have been discussed here and have used a resistor calculator on those components to discover if they are of an incorrect value, so far no such luck in finding one but i will keep looking at other areas. But again if an out of spec but otherwise correctly labelled resistor caused this could it happen twice on 2 separate boards?

 

[johnzero0]

Resistors came labelled in bags from supplier i would hope they were correct but i did not check, shame on me! but the fact that same happened on 2 boards and we could not find another fault indicates to me its possibly this type of problem.

Edit: thanks for your patience and time guys i will check rest of the board for anything that seems wrong.

 

[eh là bas ma]

if an out of spec but otherwise correctly labelled resistor caused this could it happen twice on 2 separate boards?

You told me that the first board is still populated. So it's a new board with new components, right ?

In that case it would be very unlikely that you made the same mistake twice. Unless you misread a value, or made the same confusion with the same part twice... like a 100uF instead of 10uF, etc.

 

[johnzero0]

like a 100uF instead of 10uF, etc.

This is exactly what I'm thinking...

 

[eh là bas ma]

This kind of mistakes with values happens to everybody, especialy when we're going too fast or when we are working in an altered state.

In your case I would bet on a soldering issue. I'd bet 30 euros !

We can't stress enough the importance of a good solder joint. Even the tiniest piece of hair can create a short, even the best looking pad can hide a cold joint or some strange phenomenon, resulting in a bad connection.

Once you have posted a fresh picture of a clean board with some obviously reliable soldering everywhere, I'll be glad to suggest you to check your pots values and such, but I am not sure you are already there yet. I even reluctantly wrote some "oh !" and some "ah !" on your last one...

 

[eh là bas ma]

This looks also quite suspicious.

If you don't have pcb mount potentiometers, I think you should use short wires to connect them to the pcb pads. And carefully tighten the wired pots to the enclosure, so that their body won't touch anything inside.

 

[johnzero0]

Thanks eh la bas ma for your guidance and continuing with this - i think i have made a breakthrough!

i have found a a few culprits - 4k7 is NOT the same as 47k and most likely i have also put 4k7 in place of a 47k the same on both boards ...oh boy!

 

[eh là bas ma]

i have found a a few culprits

Congrats. That's never easy, well done !

Thanks eh la bas ma for your guidance and continuing with this

You're welcome. I am merely trying to give back to the community a little of what it has brought me.

A better observer than me would probably have spotted these resistors and help you fix your build much sooner...

 

[johnzero0]

Going to mark this solved, i replaced the 47k with 4k7 and the volume control started working however i still had extremely low volume, i checked the board and i had 220k in place of a 10k at r31 you can see in the original pictures.

Finally for reference and just incase anyone has a similar issue my Q4 readings are attached. thanks all

Eh la bas ma you owe me 30 euros!
You probably gave me at least 30 euro worth of your time over these weeks so we can call it even lol

 

[eh là bas ma]

Eh la bas ma you owe me 30 euros!

As childish as I may sound, you never said you took the bet. Moreover, i've bet on a soldering issue, and you soldered some resistors on the wrong pads : That's exactly what i meant, it's a well-known kind of soldering issue.

I think i won ?

Glad you could sort things out, I wish you lots of fun with your new overdrive !

...and i wonder what will you build next ?

 

[Wizardofwoz66]

Going to mark this solved, i replaced the 47k with 4k7 and the volume control started working however i still had extremely low volume, i checked the board and i had 220k in place of a 10k at r31 you can see in the original pictures.

Finally for reference and just incase anyone has a similar issue my Q4 readings are attached. thanks all

Eh la bas ma you owe me 30 euros!
You probably gave me at least 30 euro worth of your time over these weeks so we can call it even lol

So did you actually fix this? I'm having a similar issue and have not been able to chase it down. I've built a ton of pedals at this point (200+) so my troubleshooting skills are pretty solid lol, my voltages are reasonable and all the solder joints look fine, I reflowed them just in case. The boost section works great, but the main effect I get a noticeable volume drop even at max volume max gain and there's no clipping whatsoever

 

[eh là bas ma]

I'm having a similar issue and have not been able to chase it down.

I think you should start a new troubleshooting thread, with pictures, voltage readings, schematics, etc.

 

[Wizardofwoz66]

I think you should start a new troubleshooting thread, with pictures, voltage readings, schematics, etc.

I can do that, but I first wanted to see if they ever actually solved their issue

 

[johnzero0]

I can do that, but I first wanted to see if they ever actually solved their issue

Check your resistors and then..... check them again!

i made 2 mistakes related to the values of resistors which caused the low output on the normal channel. i described the exact resistors with pics earlier in this thread.