[Billy]

D4 seems fine I’d try reflowing R28

Good news is parts of the circuit are doing what they’re supposed to do e.g. the voltage divider R29 and 30 is halving the voltage and IC3 is working regulating the voltage so as is normal its more than likely something simple like one or more dry solder joints

 

[Billy]

All your IC v+ are 7.14v what voltage do you get on D4 if your power in is 8.97v you seem to be dropping almost 2v

The solder joints on R28 look a little suspect so I’m thinking if you’ve got that voltage going in then your power to IC 1, 2 and 3 is only 7.14v it must be dropping prior to that and looking at R28 id suspect that if D4 is ok

That still wouldn’t account for no effect however or the low output on pin 14 IC2 but one thing at a time and I’m sure we’ll get there

[Billy]

What are you using to power it your voltage going in is low at 7.14v

 

Your output on pin 14 of IC2 is really low check it’s seated correctly in its socket and check the underside to make sure all the socket pins are through the solder pads all pins except 4 and 11 should read around 4.5v half power supply given that your power in is 7.14v most of yours are reading around half power so pin 14 being that low will affect everything after it

Its very easy to bend socket and IC pins

and in your picture we can’t quite see all of pin 14

 

 

[Billy]

From your picture you still have the jack socket wiring wrong you can first of all remove the orange and yellow wires from the main pcb to the jack sockets they are not needed if using a 3PDT board and then swap the red and black on the IN socket and orange and yellow on the OUT socket around

This has to be right before we can debug any further the fact that you still dont get any effect signal may be due to another fault

You can put a jack into the socket as in the picture to see where the tip (signal carrying wire) connects to and in turn which solder lug should be used so all you have to do is swap those wires around on the relevant IN and OUT sockets

[Billy]

Barry has a soldering video if you watch that it’ll give you the confidence to get you soldering like a pro in no time it’s really not that difficult it is important that your soldering iron is suitable for pcb work up to about 30 watts even better if it has a temperature control, solder is also important I never use unleaded but if i have to I also use flux to help it melt better

The crash course also on the guides page explains information on soldering irons etc

Watch it here

The GUIDES PAGE – Mandatory Reading for all!

 

[Billy]

Hi Ben

Welcome to the forum

There are a few possibilities of what could be wrong

We’d need clear in focus pictures of both sides of the board and off board wiring so that it can be traced easily

[Billy]

Do you lose volume on all positions of the diode switch you will get a drop in volume depending on which position it’s in the middle should be the loudest

Check the solder joints on the output jack lugs make sure the solder flows nicely the solder on your tip looks like it could be dry

Where do you loose volume in the circuit

[Billy]

You can’t accurately measure components in circuit whilst they are connected to other components

Much better to do a visual check of your components ensuring they are the correct value and polarity is correct

You can check resistors by colour band I use this site

https://samstechlib.com/610938/en/read/

I’ve checked the components I can see all seem to be correct value and polarity

I’ve roughly traced the audio path for you below you want to follow the red line from input to output the simplest way to check is from the IN T pad through C1 and R2 into pin 3 IC1A out pin 1 to P1 lug 2 out lug 3 to C5, R5 into pin 6 IC1B out of pin 7 to C7, R7, C8, C9, R9 into  P2 lug 3 out lug 2 to IC2B pin 6 out pin 7 to C11, R12 into P3 lug 3 out lug 2 to the OUT T pad that way you’re checking all the inputs and outputs directly

Make sure you make good connections when probing you will notice differences in audio for example at the IN T pad it will be clean signal and as you go through amplification stages etc it’ll get louder

Set your volume low to save you jumping out of your skin! If you have a looper pedal record a loop and use that as your input audio to keep 2 hands free

Read the audio probe explained PDF and you should be fine

[Billy]

To test you are getting power to the main Cap’n munch pcb set your meter to 20V DC place your black probe on the ground pad and your red probe on the +9v pad

If your LED illuminates that would mean you are getting power to the 3PDT board so doing this is just to check you are getting power to the Cap’n munch pcb via your jumpers

[Billy]

Are you getting power to the main board , it’s hard to see but your wires on the DC jack look fairly close can’t really see if you’ve got big blobs of solder shorting those wires and also cant really see where the DC jack wires go to

I’m assuming they go to the 3PDT board +9v and ground pads and power and ground are then jumpered from there to the main pcb so I’d check that first on the main board +9v and ground pad to ensure it’s getting power

You’d get bypass signal with no power it basically means that your jacks are wired correctly to the bypassed side / throw of the 3PDT

 

 

[Billy]

All correct, R12 would intially be a jumper until you decide if the inputs to high then you would change it to a resistor between 47 to 100K i’d use sockets till you find what you like, regarding the common anode bicolour LED it doesn’t really matter which way around you solder the cathodes it’ll still work

You only have to consider it if you want a specific colour for bypass and effect on

[Billy]

With a battery you shouldn’t get any noise

A power supply will add noise from AC ripple if it’s not filtered and will put out more voltage if it’s not regulated very few cheap ones put out 9v I’ve had them as much as 14v

You’re much more likely to get noise with higher gain pedals I use a battery a cheap adaptor and a boss adaptor to demo my pedals just to show you can get significant noise with cheap adaptors most musicians don’t have the faintest idea how cheapo equipment can affect their set up

There is filtering in the circuit if you look at the power section C7 check that’s got good solder joints

[Billy]

Typing at the same time Jeff!

That’s great it’s sorted

I always advise people not to go for the cheap option when it comes to pedal power mine are all boss filtered and regulated they cost 3 times as much but save a lot of hassle and unwanted noise

Make yourself a few of the battery snap connectors really cheap and always handy if your power supply goes South

Where are you located they’re cheap as chips at

https://www.bitsbox.co.uk/index.php?main_page=product_info&cPath=225_232&products_id=2365

[Billy]

 

Sounds like it could be something to do with your power supply the only way to know for sure is to either get a 9v regulated and filtered power supply or use a battery with it being present at pin 3 ie audio into the op amp that tells me it’s there at the clean signal input and is then being amplified

Check if you get it on the pcb input pad and R1 and C1 that’ll let us know if the noise is there prior to going into the effects circuit

[Billy]

Did you check your cables using other pedals

I’m not sure I follow are you saying with your 4 track fuzz disconnected you still get a squeal

You should get audio at pin 1 it being the output, you do sometimes need to mess around to get good contact with your probe

Is your guitar fitted with humbuckers or high output pickups

[Billy]

No don’t swap anything out the idea is to use your audio probe to see where the squealing starts

You should get clean signal with no squealing into IC1A pin 3 if you then get squealing out at pin 1 and in at pin 2 that would indicate your problem lying in the feedback loop components between pin 1 and 2 as i say the idea is to try and locate where it starts

45 watt is a little to hot for pcb work I wouldn’t go more than 30 watt

Your pedal works so you’ve built it correctly and it’s just a case of finding where or what is causing the squeal is it present throughout the range of the gain pot and does any pot alter it

Regarding the power supply I always use a filtered, regulated supply and never the non regulated cheaper option especially with high gain circuits using a battery means pure DC so no unwanted noise from AC ripple as I’ve said im not sure if 1.5v over bias voltage is enough to make an op amp oscillate

Just for future reference I use these to test with batteries to rule out the supply being the problem

 

 

[Billy]

The next thing I would personally do Jeff is try to track down where it starts

Op amps will go into oscillation if they are being fed incorrect voltages as I said a few things could cause it dry solder joints, incorrect values etc  I’m not 100% a volt over VA, VB 4.5v would cause it that is why I suggested trying a battery to rule that out or a regulated 9v power supply

I would first of all use an audio probe and check audio going in at IC1A pin 3 where I wouldn’t think you’d get it then check pin 1 output where you may get it that at least will give you the area to look at

Some of your solder joints do look suspect

Where did you get the TL072 and what wattage is your soldering iron I also note that R2 and a few of your 10K resistors are 1/2 or 1 watt size R2 is in the IC1A feedback loop so it could be with its thicker legs it’s not making good contact with the pcb

[Author]

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