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.
Hello, welcome !
I think a good start would be to make some adjustments on the soldering side. I circled some of the most suspicious solder joints (red) and some probable shorts (green) mostly coming from tiny bits of solder remaining on the pcb, between pads.
I would reflow all suspicious pads, so that the pad is filled with solder : not too little or too much, just enough. This is how you can ensure a good connection between your components and the board. Your iron (set around 400°C) needs to touch and heat simultaneously the component's leg and the pad for 1 or 2 seconds, then you can put a little bit of solder to fill the pad. Finally, lift up the iron along the component's leg to make a dome-shaped solder joint.
Almost all your pads need some care : use your desoldering pump to remove the excess of solder on the pads with bubble-shaped soldering joint.
Next, clean the tiny spaces between pads, moving quickly with your iron to avoid overheating the pcb. Remove all heat-sensitive components, such as transistors and IC. An old dry toothbrush can also be useful to clean the board from all remaining solder bits.
With your digital multimeter (DMM) set on continuity test, following the schematics, you can make sure there is no connection between components that aren't supposed to be connected (shorts). Power supply unplugged and circuit unpowered, switched off.
If you still have an issue after this, some voltage readings will be helpful to narrow it down. Here is a useful link to learn how to post your readings, among other things :
Thanks el la bas ma, have cleaned up and reflowed all suspicious pads continuity test seems fine and have looked through magnifying glass for bridges but still no joy.
Voltages readings from which components would help?
Could you post a new picture of the soldering side ? An other picture with everything installed in the enclosure, could help to spot an issue with the wiring, or jacks, 3PDT, etc.
Q1, Q2, ... all transistors, and check if the LT1054 pin 5 reads 18V.
As mentioned in the link posted in reply #2 :
"Now, using the original schematic as a reference for which part is which (that is, which transistor is Q1, Q2, etc. and which IC is IC1, IC2, C1, and so on) measure and list the voltage on each pin of every transistor and IC. Just keep the black lead on ground, and touch the pointed end of the red probe to each one in turn. Report the voltages as follows:
Q1
C =
B =
E =
Q2
C=
B=
E=
IC1 (or U1)
P1
P2
P3
.
.
.
And so on until you get through them all. Having gathered the data, post a tidy list of it on the forum, and you'll most likely have a working effect soon. "
Thanks again eh la bas ma, not sure if you can see my other pics in start of this thread but there are 2 of the board connected up inside enclosure.
I will continue with taking the rest of the readings but so far something is off on the IC im not getting 18v on p5 (thank you for the handy pic of the IC!)
You need to fix this before taking more voltage readings, as long as transitors aren't fed properly, you can't expect good values.
You can start by trying an other LT1054 (I think I remember reading something about Tayda voltage pumps and regulators being untrustworthy). Where did you buy the LT1054 ?
Or check carefully all connections around this IC, according to the schematics.
Assuming the LT1054 is ok, this is the part of the circuit you should check carefully :
First check all connections with your DMM (multimeter) on continuity mod, then start the hunt for shorts around these components. Power supply unplugged.
Edit : ...and you'll need more solder to fill the pads on both 3PDT footswitches.
Thanks again, have applied more solder to the 3pdts and have performed continuity check on the components in your screenshot a few i wasnt sure what they were i have circled those the others check out fine
I have also tried another IC both from Mouser, i wonder could it be an incorrect value of one of these components that is reducing the voltage on pin 5 of the IC?
Hi all! I have just finished building the Pharmacist. This is my first time sourcing my own parts and drilling the enclosure. I took my time and kept the soldering pretty neat i think? Be gentle! The pedal works (and sounds great) on the regular side, however the LED has a slight flicker to it...
forum.pedalpcb.com
You'll see how the soldering should look like, and you'll find some voltage readings reply #17.
And according to these voltages readings, the circuit should be running at 18 V...
Edit : I noticed all polarized capacitors are supposed to be calibrated at 25V minimum (so the circuit can run at 18V), did you check all electrolytics before populating the pcb ?
The Vcc and Vref designations are inner networks inside the circuit (so is Ground), you'll find them on various locations on shematics. For exemple, all Vref points should have continuity.
SWGND (switch ground), near Led1 and Led2, are connections to both 3PDT. That's how both status leds are activated when you press their respective footswitch.
Edit 2 : it's always safer to measure all resistors before populating the board. This way you won't have any doubts and you won't have to desolder them to check their value. Capacitors values are usually written on them, for resistor, you can use some free software like this :
Well, i just opened a circuit running internally at 18V, and I have similar values on the LT1054. Pin 5 is grounded. It's only further in the schematics that i can read some higher voltage.
Sorry if I wasted your time with this LT1054. It's both the IC and the associated caps and diodes that are increasing the voltage. Your IC should be ok. Try to probe other locations, like Vcc, to see if you read some voltage above 9V.
In my case, on a different circuit with a charge pump going up to 35V, it was at R27 that I could read 35V :
Thanks eh la bas ma, no problem about the IC just glad i got some advice ill take some transistor readings still not sure about a vcc location that i can get a reading above 9v. Im going to clean board with some isopropyl alcohol, is there anywhere i can compare voltages to working circuit?
I had taken a reading of 15.79v from a cap to the right of the IC i will post which exact one along with reading from c24 later . and after Further testing the boost is working great its just boosting a kind of clipped sound
[DIY Fever] Audio Probe - very simple contraption that helps with debugging audio circuits
diy-fever.com
This is one of the most useful debugging tool.
You need to follow the signal path, and look for a suspicious location, for exemple somewhere where the volume drops down.I think that's the signal path.
I could have missed something, though. You can probe other part of the schematics, but don't probe the power section (everything around the IC LT1054, Vcc, Vref).
Audio probing can create some popping and unconfortable noises, so it's recommended to do it at low volume on a cheap amp. Circuit powered and switched on.
Edit : check also if there isn't any shorts on the In, Out and ground pcb pads :
Hoping you already have reflown all potentiometer's pads, as mentioned in reply #2.
Are you sure there aren't any confusions with the pinouts ? (I am not saying there are, but just in case...).
For exemple, on Q4, you can read 0V on pin 2 where it's connected to ground according to schematics. Gate is the side with an arrow as symbol on schematics.
Q5 pin 2 and Q4 pin 1 should read the same voltage, as you can see on schematics, because they are directly connected. That's probably your 17V.
There is a simple way to know what are Drain and Source :
1/ You know the transistor pinout, here it is :
2/ You know the transistor orientation, because it's printed on the pcb :
3/ With a continuity test, see what transistor's pad is connected to the following component on schematics, and you'll know the leg's designation in number. Then look it up on the real pinouts with letters.
For exemple, on Q4, pin 2 is connected to R25. So you can deduce what is pin 2 (Drain or Source) by testing which leg rings with R25, and then, look to the pinouts picture above.
Edit : I wonder why @PedalPCB always write 1, 2, 3 on schematics instead of G, S, D or E, B, C... Isn't it just a bit harder to decipher ? Is it on purpose so we can have a real challenge ?
Edit 2 : I may have possibly noticed something odd about Q2 :
According to schematics, Q2 pin 3 should be connected to Q3 pin 2 and thus read the same value.
However, that's not happening on your readings.
In this case, I would promptly perform some continuity tests to check the whole aera. I guess there're grounds for reasonable doubts about this transistor... You might have a bad connection or a short somewhere...
Edit 3 : Remember IC and transistors are heat-sensitive, you can't apply heat around them for too long (2 or 3 seconds max).
