SOLVED Caesar Chorus No Audio But LEDs All Work

[SleezyLobster]

I've been working on the Caesar Chorus as my first build since I'd tried to make something easier but left out a capacitor and a pot in my order so I transitioned to this one. So my first mistake was that my 5mm LEDs were in backwards and I fixed that so now my internal 3mm LEDs and my 5mm LEDs all work and flash with the rate knob, and when I turn the pedal off I can get sound through even though there is a little hum. However, when I turn on the pedal the hum gets slightly worse and I get no signal. I tried checking continuity throughout and I would get beeps but sometimes it would only be on one of the legs of components and not the other but further down the signal path it would still be working so I'm not sure if that's a problem. I've also built an audio probe but when I plug it in I get a really bad hum that gets worse when I touch components. It used to go away when I'd touch the tip of the input jack but now even that hums and all I changed was the LEDs. When it would be quiet, I could only get to the first capacitor before it would just buzz regardless of whether or not I was touching the leads, and the solder joints seemed fine for it but I also don't really know how to use a DMM or the audio probe. Also while I was soldering I kept having problems with the solder sticking to the iron and not wanting to flow onto the pad. It only happened to a few of the pads and when I tried to increase temp, add more flux, and reflow it it still would do it only for those pads. That's why some of them look so messed up but I'm hoping they still have a solid connection. I've messed with all the pots including the trim and there was nothing. Does anyone see any apparent issues or know what I'm doing wrong while audio probing? Also my DMM is a UNI-T UT133B and it doesn't have a frequency thing like I've heard someone suggest before.

 

[eh là bas ma]

Hello, welcome !

Red : probably not enough solder
green : probable shorts (use your iron to remove the remaining solder bits between pads, do it quickly to avoid overheating the pcb)
blue : probable bubble-shaped solder joint


I'd suggest to set your iron around 400°C, clean the tip with some half-wet-almost-dry sponge when it's dirty. You're supposed to clean it quite often during the building process. It depends on the solder and the iron, but i'd say every 10 soldering joints or so. If the iron's tip is smoking, clean it. Don't forget to protect your eyes, and get some ventilation in the room, don't breath the fumes.

Use an old dry toothbrush to clean the pcb from solder residues, dirt, pieces of hair, etc...

Please, don't forget to post a link to the schematics in your troubleshooting posts.

https://docs.pedalpcb.com/project/PedalPCB-Caesar.pdf

First thing to do is to check your ground network : pedal unplugged to the power supply, continuity test between all the main grounded points : jacks, 3PDT footswitch, DC power jack, pcb's ground pads, etc. They should all ring together. One of the jack's tip may be grounded too when the circuit is switched off.

Then you'll have to check if the board is correctly powered : power supply plugged in, circuit turned off, look at schematics, you should have +9V at D100 positive side, or C104 positive side.

Audio-probe is a great tool to quickly find where the signal disappears or does something suspicious. First you need to find the signal path. Quickest way is to draw the shortest line from IN to OUT. The signal may go in other aeras, but you are trying to find the issue by narrowing it down. You don't need to check every components at first.

How to build and use an audio probe : https://diy-fever.com/misc/audio-probe/

The audioprobe's ground terminal needs to be grounded or it will create a loud noise : use the pedal's output jack's ground, it should be free because your amp is connected to the probe. A crocodile clip is quite useful for the audioprobe's ground, you won't have to hold it with one hand.

You need to have some kind of signal going through the circuit : connect the circuit's input to a loop station like Boss RC3 or something that can generate a signal. A guitar is fine but it will be hard to keep playing while you probe the circuit.

Circuit powered and switched on. Check here and there following the signal path from IN to OUT. If your signal disappears at some point, that's when you need to check everything before that point, in order to find the precise location where it stops.

As soon as you find the precise location where it stops, you are much closer to debugg the device. Now you can perform more tests in the aera, looking for the issue (visual inspection, polarized component's orientations, audio-probing and continuity).


Signal path is in red. Clock section in blue. The aera at the bottom with no colors is the power section, don't use your audioprobe there.

If the signal is fine until the clock section and disappears at this point (for example : signal at R24 but no signal at R31) then you'll have to check the blue path which is the clock section, including the two ICs (v3207 and v3102).

You may also post some voltage readings as described in these very useful troubleshooting instructions, written by a famous electro-wizard :

DEBUGGING - What to do when it doesn't work

DEBUGGING - What to do when it doesn't work

www.diystompboxes.com

 

[temol]

One comment - when audio probing you won't find any signal on the opamp inverting inputs (pin 2 and 6 of the IC2). That's normal.

 

[bhcarpenter]

One more thing- on the Caesar there’s often a very narrow range on the trim that pot where things work. Unlike a lot of pedals, on this one when the trim pot isn’t in the operational range the pedal doesn’t work at all. Good luck!

 

[synthesiserror]

I don't think the middle leg of your blend knob is soldered to the pad at all. Definitely re-flow that one.

 

[Bio77]

Can you double check your foot switch and jack wiring? Also, verify that, when you are testing, the guitar and amp are connected to the right jacks (I've made that mistake before). No signal at all usually indicates a wiring problem or a short to ground. The hum gives me this impression too.

Audio probe is basically a way of outputting a test point in the circuit to your amp. If you audio probe C1 in the circuit, when you play your guitar you should hear it. If not, definitely a wiring problem. If C1 has signal, check C5 in the clean path next.

 

[SleezyLobster]

So using the DMM I did DC and at 600 I'm not quite sure what that means but D100 read 9.2V and C104 read 8.8V so I'm not sure if that's a problem. My audio probe still just gives a bad hum but goes silent when I touch C1. I can hear guitar when I touch the tip though. I checked and my wiring is like the diagram from PedalPCB. With my jacks the sleeve goes to the board and the tip goes to the footswitch so I think that's right. DC jack looks like how it look in the diagram.

 

[SleezyLobster]

I don't think the middle leg of your blend knob is soldered to the pad at all. Definitely re-flow that one.

There's a decent amount of solder on the component side is that fine or should I have both sides?

 

[SleezyLobster]

One more thing- on the Caesar there’s often a very narrow range on the trim that pot where things work. Unlike a lot of pedals, on this one when the trim pot isn’t in the operational range the pedal doesn’t work at all. Good luck!

At one point the trim pot sounds like I tripped an alarm and gets all angry and at another point it pops a bit but other than that its silent.

 

[SleezyLobster]

Hello, welcome !
View attachment 65643
Red : probably not enough solder
green : probable shorts (use your iron to remove the remaining solder bits between pads, do it quickly to avoid overheating the pcb)
blue : probable bubble-shaped solder joint
View attachment 65644

I'd suggest to set your iron around 400°C, clean the tip with some half-wet-almost-dry sponge when it's dirty. You're supposed to clean it quite often during the building process. It depends on the solder and the iron, but i'd say every 10 soldering joints or so. If the iron's tip is smoking, clean it. Don't forget to protect your eyes, and get some ventilation in the room, don't breath the fumes.

Use an old dry toothbrush to clean the pcb from solder residues, dirt, pieces of hair, etc...

Please, don't forget to post a link to the schematics in your troubleshooting posts.

https://docs.pedalpcb.com/project/PedalPCB-Caesar.pdf

First thing to do is to check your ground network : pedal unplugged to the power supply, continuity test between all the main grounded points : jacks, 3PDT footswitch, DC power jack, pcb's ground pads, etc. They should all ring together. One of the jack's tip may be grounded too when the circuit is switched off.

Then you'll have to check if the board is correctly powered : power supply plugged in, circuit turned off, look at schematics, you should have +9V at D100 positive side, or C104 positive side.

Audio-probe is a great tool to quickly find where the signal disappears or does something suspicious. First you need to find the signal path. Quickest way is to draw the shortest line from IN to OUT. The signal may go in other aeras, but you are trying to find the issue by narrowing it down. You don't need to check every components at first.

How to build and use an audio probe : https://diy-fever.com/misc/audio-probe/

The audioprobe's ground terminal needs to be grounded or it will create a loud noise : use the pedal's output jack's ground, it should be free because your amp is connected to the probe. A crocodile clip is quite useful for the audioprobe's ground, you won't have to hold it with one hand.

You need to have some kind of signal going through the circuit : connect the circuit's input to a loop station like Boss RC3 or something that can generate a signal. A guitar is fine but it will be hard to keep playing while you probe the circuit.

Circuit powered and switched on. Check here and there following the signal path from IN to OUT. If your signal disappears at some point, that's when you need to check everything before that point, in order to find the precise location where it stops.

As soon as you find the precise location where it stops, you are much closer to debugg the device. Now you can perform more tests in the aera, looking for the issue (visual inspection, polarized component's orientations, audio-probing and continuity).

View attachment 65645
Signal path is in red. Clock section in blue. The aera at the bottom with no colors is the power section, don't use your audioprobe there.

If the signal is fine until the clock section and disappears at this point (for example : signal at R24 but no signal at R31) then you'll have to check the blue path which is the clock section, including the two ICs (v3207 and v3102).

You may also post some voltage readings as described in these very useful troubleshooting instructions, written by a famous electro-wizard :

DEBUGGING - What to do when it doesn't work

DEBUGGING - What to do when it doesn't work

www.diystompboxes.com

Also is it normal for the ground to only be for one leg of the components since that one would be the one leading to ground anyway? Because some resistors for example only had continuity on one side.

 

[eh là bas ma]

is it normal for the ground to only be for one leg of the components since that one would be the one leading to ground anyway?

Testing for continuity between R1 and C1 : your meter (set on continuity mode) should ring at only one R1pad, the pad that connects this resistor to C1. There can't be continuity between the two sides of a single component. In other words, on the pcb R1 has two pads, one for each leg, they shouldn't be connected together, unless the schematics says so. According to the schematics, there is no continuity between R1 #1 and R1 #2.

There are little black dots between each components. On the schematics, they symbolize a connection.

Here, one side of R1 is connected to C1 and IN, the other side of R1 is connected to Ground. The side connected to Ground isn't supposed to be connected to C1 and IN.

I checked and my wiring is like the diagram from PedalPCB

Make sure there isn't any tiny little piece of wire that have missed the hole, sometimes it's almost unoticeable but some thin stray wire is shorting the next pad. Make sure there isn't any soldering residue, or dirt that could create a short between the wiring pads on the pcb.

Remember that even a tiny piece of hair can create a short, the space between each pads has to be as clean as possible.

Use your iron to clean between pads, dont forget to be very quick, to avoid overheating the pcb and the heat-sensitive parts like transistors and ICs (that's why sockets are quite useful). Use an old toothbrush to clean the dirt when it's not some soldering residue.

Sometimes you'll see a dark/brown circle around your soldering pad : that's flux residue. You don't need to worry about it (but it's not traditionnaly seen by the diy community as a good thing, it could oxydate in 20 years and damage the pcb, a great master pedal builder would clean it with izopropil alcohol).

There's a decent amount of solder on the component side is that fine or should I have both sides?

If there is an issue on a circuit, the "better safe than sorry" rule applies.

You're supposed to solder your parts on the soldering side. There are traces on the pcb (these dark lines going from one pad to another, like little roads on both sides of the pcb), creating all the connection's networks, you don't want to miss the connection between your component's leg, the pcb pad, and the pcb trace.

 

[Locrian99]

Bbd’s without sockets make angels cry.

 

[synthesiserror]

There's a decent amount of solder on the component side is that fine or should I have both sides?

The way it's balled up makes me think the pad didn't get hot enough. You don't need to add more solder, just re-heat that joint for a few seconds and it should flow to the other side. Try to heat the pad and the leg at the same time.

 

[chris.knudson]

Also while I was soldering I kept having problems with the solder sticking to the iron and not wanting to flow onto the pad.

What is the condition of your iron tip? Solder not wanting to flow could mean that your tip isn't getting hot enough. That can be caused by a number of things. For example, if your tip is corroded or dirty or if your tip isn't screwed on securely. It could also have to do with the temperature that you have your iron set at - I typically keep mine at around 680F (don't know what that translates to in Celsius).

Also, if it is only happening with the larger components, keep in mind that the time it takes to transfer heat to larger components can be impacted by the size of your tip. The smaller your tip, the longer it takes for heat to transfer. Just something you might want to check if you're having trouble getting solder to flow properly.

EDIT: If you're using lead free solder, it typically melts at higher temperatures and does not stay in a molten state for as long, so it's a little harder to work with. Personally I prefer 60/40 tin/lead, rosin-core solder.

 

[Bio77]

So using the DMM I did DC and at 600 I'm not quite sure what that means but D100 read 9.2V and C104 read 8.8V so I'm not sure if that's a problem. My audio probe still just gives a bad hum but goes silent when I touch C1. I can hear guitar when I touch the tip though. I checked and my wiring is like the diagram from PedalPCB. With my jacks the sleeve goes to the board and the tip goes to the footswitch so I think that's right. DC jack looks like how it look in the diagram.

If I'm reading this correctly, you audio probed C1 and heard guitar? If so, do you hear guitar at C5?

 

[SleezyLobster]

What is the condition of your iron tip? Solder not wanting to flow could mean that your tip isn't getting hot enough. That can be caused by a number of things. For example, if your tip is corroded or dirty or if your tip isn't screwed on securely. It could also have to do with the temperature that you have your iron set at - I typically keep mine at around 680F (don't know what that translates to in Celsius).

Also, if it is only happening with the larger components, keep in mind that the time it takes to transfer heat to larger components can be impacted by the size of your tip. The smaller your tip, the longer it takes for heat to transfer. Just something you might want to check if you're having trouble getting solder to flow properly.

EDIT: If you're using lead free solder, it typically melts at higher temperatures and does not stay in a molten state for as long, so it's a little harder to work with. Personally I prefer 60/40 tin/lead, rosin-core solder.

I've been using the kester 63/37 and I'm at 680F. My tip is brand new since I'm just starting and if the solder oxidizes or I burn some flux on the tip I would clean it off but the behavior of solder still seems to be beyond me. Also I saw some people recommending chisel tips but I felt like that was too big. I use whichever one is about the size of a pen since there is a sharper one but it wouldn't really heat well enough unless you used the side of it not the tip.

 

[SleezyLobster]

If I'm reading this correctly, you audio probed C1 and heard guitar? If so, do you hear guitar at C5?

I heard guitar at the tip,

I've been working on the Caesar Chorus as my first build since I'd tried to make something easier but left out a capacitor and a pot in my order so I transitioned to this one. So my first mistake was that my 5mm LEDs were in backwards and I fixed that so now my internal 3mm LEDs and my 5mm LEDs all work and flash with the rate knob, and when I turn the pedal off I can get sound through even though there is a little hum. However, when I turn on the pedal the hum gets slightly worse and I get no signal. I tried checking continuity throughout and I would get beeps but sometimes it would only be on one of the legs of components and not the other but further down the signal path it would still be working so I'm not sure if that's a problem. I've also built an audio probe but when I plug it in I get a really bad hum that gets worse when I touch components. It used to go away when I'd touch the tip of the input jack but now even that hums and all I changed was the LEDs. When it would be quiet, I could only get to the first capacitor before it would just buzz regardless of whether or not I was touching the leads, and the solder joints seemed fine for it but I also don't really know how to use a DMM or the audio probe. Also while I was soldering I kept having problems with the solder sticking to the iron and not wanting to flow onto the pad. It only happened to a few of the pads and when I tried to increase temp, add more flux, and reflow it it still would do it only for those pads. That's why some of them look so messed up but I'm hoping they still have a solid connection. I've messed with all the pots including the trim and there was nothing. Does anyone see any apparent issues or know what I'm doing wrong while audio probing? Also my DMM is a UNI-T UT133B and it doesn't have a frequency thing like I've heard someone suggest before.View attachment 65638View attachment 65639View attachment 65641

I finally did it it was a combination of a short and possibly a bad joint on Q5 that finally worked, along with fixing everything you guys had already mentioned. It's a mess but it works so it's been a good learning experience so thanks for the help. I think I set it to solved but can someone confirm for me that it worked?

 

[chris.knudson]

Glad you got it working. It's not showing up as Solved - at least not for me.

 

[KR Sound]

Nice work!

 

[bhcarpenter]

Congrats on knocking out your first build and your first debug! I’m sure it was frustrating, but it sounds like you learned a ton and have a great pedal as well.