Moonshot Tremolo - First Build - Where to Start Troubleshooting?

[chinless42]

This is my first build and I'm definitely a novice at this so I hope I didn't screw up too bad. I'm a little stuck trying to figure out what to do at this point.

-I get sound when it's bypassed,
-No sound when turned on
-The on/off LED turns on, the rate LED does not.

Where should I start to try troubleshooting this and try to figure out what part (or parts) went wrong?
I have a multimeter but I'm honestly not even sure what to measure (again, I'm super new to this).
Any help at all would be amazing, thanks!

 

[andrew]

Hi! Also new to the hobby, but I've had similar issues with a different build so I've picked up a tip or two. Or at least enough to help you get started.

What's worked for me is just continuity testing the heck out of it. First start with the jacks — in bypass mode, touch one probe to the tip contact of the input jack, the other to the tip contact of the output jack. You should get a tone. Then repeat with the pedal activated — if you get no tone, that confirms that there's an issue in the circuit somewhere. Repeat these steps with the probes touching the inside of the jacks, which will tell you if your ground circuit is intact. You should have a tone in both bypass and activated mode — if you don't, your ground is broken somewhere.

If your jacks and ground check out, I'd check the footswitch next. The joint marked "In" on your footswitch PCB is where the audio signal goes from the switch to the main PCB, and the "Out" joint is where the audio signal comes out of the main PCB back to the footswitch. Test these two points in both bypass and activated mode. If you have tone in bypass but no tone in activated, there is a short somewhere in your switch. If you have a tone in both, your issue is somewhere in the main PCB.

Which is where things start getting hairy.

The last easy checks to do are the pots. On each pot the left and middle lugs (when looking from the back) are the input/output lugs. The ones on the right, with the square pads, are ground. Test the left and middle lugs of each pot with your multimeter still in continuity mode. Make sure that the pots are turned up when you do this. If you get a tone, the pot is good; no tone and the pot is bad. At this stage I'm not sure if it matters whether the pedal is in bypass or active mode, so test in both.

If all your pots check out, the only thing left to do (again, to my own beginner's knowledge) is to go through and trace the circuit and test it point by point by point. I have a hard time literally tracing the circuit path on the board itself, especially when I've got everything soldered on, so this step will probably require you to be consulting the build docs, specifically the schematic.

Hope my beginner tips help! And if they don't, I hope somebody with more experience comes along soon. If you have trouble following my instructions (I know I tend to go on a bit), shout and I'll mark up different components on your photos.

 

[zgrav]

start by watching some youtube videos about how to use your multimeter. then read through some of the forum posts for other "first build" problems that have been posted, paying attention to the suggestions that were given about what to check, and how to check them.

note how many times people suggest checking the part values and how often it eventually turns out that the wrong part value was used.

also see how often people say "did you insulate your pots from touching the board?" are you SURE your pots aren't touching the board?"

keeping those things in mind, you are going to want to use your multimeter to find out if your IC is getting power, since you are not getting any sound when the effect is engaged. so post the readings you get for each pin on your IC.

in addition to getting the sound path sorted out, you will need to figure out why the rate LED is not flashing. use your meter to see if the LED is getting power. if it is getting power but not flashing, you might have installed it backwards.

 

[zgrav]

also worth noting -- nice neat job on your build. it will make troubleshooting and getting it to work much easier.

 

[fig]

I think the LDR should be facing the LED.

I also suggest using sockets for ICs.

 

[zgrav]

I think the LDR should be facing the LED.

I also suggest using sockets for ICs.

I agree with both of those suggestions, but the LDR will work when boxed up even if it is not facing the LED. but that is an issue after the LED is flashing properly with the rate and depth controls. and no reason to remove the IC and put in a socket now if it is installed properly.

 

[fig]

I concur

 

[Mcknib]

First thing to do as advised is a visual check make sure all components are the correct value and oriented correctly

Check your solder side of the board under magnification and good light looking for dull or ball like dry solder joints and solder bridges (stray solder or wire strands that can form a bridge and accidentally connect components that shouldn't be connected)

Make sure your power supply is centre negative if it is then

Check you get power to the pcb + and - pads set your meter to 20V DC place the black probe in the COM socket and your red probe in the V for voltage socket

Put your black probe on the pcb - (ground pad) and your red probe on the + (power pad)

Learning resistor colour band values is not that difficult there are only 9 of them + tolerance / multiplier gold and silver fortunately you've used all 5 band metal film so you know the last band is brown for + or - 1% tolerance

Here's a value calculator

Sam's Tech Library

samstechlib.com

Again as advised read and watch tutorials then read and watch tutorials then........

Let us know how it goes with these checks

All of your values look correct to me but like anyone else I can miss something the more it's checked the better so do your checks and get yourself used to it