I want to troubleshoot a possible probematic footswitch

[pfapin05]

I have a tubescreamer clone pedal and it works when bypassed, but when the footswitch is engaged it does not work. I would like to know how to bypass the switch to see if the pedal works. Can I just hook a jumper cable from input to output jack or will that not work? Im so sorry if this is something simple, but I want to learn more about troubleshooting I just cant find any videos on youtube that can help with this subject.

I have a picture here and I hope its clear enough for all of you. From the footswitch there is 2 wires going to input and output jack, 2 wires going into each side of the main pcb board, one wire going to the small pcb board which looks to be the board for activating the light, and one jumper wire on the switch itself. If I wanted to test the pedal without the footswitch in the equation, would I be safe to assume that I could solder the wires between the input and output jack, and also solder the wires together that go in each side of the main pcb board? I dont have the stuff to make an audio probe right now, so that is out of the equation.

Any help is appreciated and thank you in advance!

[DIY Bass]

If you have a mutimeter you can measure the resistance between the switch contacts and make sure the contacts are conducting where they need to.  You could also use a jumper to connect the input jack straight to the input of the board, and then connect the output of the board straight to the output socket.  To be honest though, If i had a pedal that I had just finished and it worked in bypass but not when the effect is turned on, I would be assuming that I had made an error in the board somewhere and would start looking for that error.

[ElectricDruid]

Did you test the board before you wired the switch up? Do you know the circuit is ok?

If not, like DIY Bass said, the problem is likely to be something up with the circuit, not the switch.

If you did test the circuit and you're reasonably sure that's ok, check the wiring. Then check it again, because it's a weird quirk of human psychology that we mostly see what we think is there and not what actually is.

Another approach would be to take an http://diy-fever.com/misc/audio-probe/ and see if you can follow the audio through the switch contacts to the PCB input. If the board is working, it'll reappear at the board output and then go back to the switch and finally to the output. Except that since it isn't working, one of those steps won't happen, and that'll tell you where to start looking for the problem.

[pfapin05]

The pedal was working before I obtained it. The original owner said that he used to use it and it worked fine until one day he went to step on the footswitch and he heard a loud pop and then the pedal started humming with no guitar signal. I dont hear a humming or anything like that so Im unsure what he was talking about, all I hear is a very slight hissing noise when all the pots are turned all the way up. I have a picture here and I hope its clear enough for all of you. From the footswitch there is 2 wires going to input and output jack, 2 wires going into each side of the main pcb board, one wire going to the small pcb board which looks to be the board for activating the light, and one jumper wire on the switch itself. If I wanted to test the pedal without the footswitch in the equation, would I be safe to assume that I could solder the wires between the input and output jack, and also solder the wires together that go in each side of the main pcb board? I dont have the stuff to make an audio probe right now, so that is out of the equation.

[pfapin05]

Did you test the board before you wired the switch up? Do you know the circuit is ok?

If not, like DIY Bass said, the problem is likely to be something up with the circuit, not the switch.

If you did test the circuit and you're reasonably sure that's ok, check the wiring. Then check it again, because it's a weird quirk of human psychology that we mostly see what we think is there and not what actually is.

Another approach would be to take an http://diy-fever.com/misc/audio-probe/ and see if you can follow the audio through the switch contacts to the PCB input. If the board is working, it'll reappear at the board output and then go back to the switch and finally to the output. Except that since it isn't working, one of those steps won't happen, and that'll tell you where to start looking for the problem.

The pedal was working to begin with, and the original owner said he stepped on the footswitch one day and heard a loud pop and then a humming noise. I dont have the stuff to make an audio probe right now, but I will eventually do that. Ive added some pictures and had a quick question though, would I be able to just solder the input and output jack wires together from the footswitch and solder the 2 wires together that go in both sides of the main pcb from the footswitch together to bypass the footswitch and test to see if the pedal works?

[pfapin05]

If you have a mutimeter you can measure the resistance between the switch contacts and make sure the contacts are conducting where they need to.  You could also use a jumper to connect the input jack straight to the input of the board, and then connect the output of the board straight to the output socket.  To be honest though, If i had a pedal that I had just finished and it worked in bypass but not when the effect is turned on, I would be assuming that I had made an error in the board somewhere and would start looking for that error.

Would you please look at the pictures and tell me what you think the input wire to the board is and the output wire to the board is? The green wire from the footswitch goes into the right side of the board and the baby blue wire from the footswitch goes into the left side of the board, and Im guessing facing the internals of the pedal, the output jack that goes to the amp is on the right and the input jack that goes to guitar is on the left, correct? If you dont mind, would you please take a look and tell me which wires to hook up together again to bypass the footswitch and test the pedal out? I really appreciate it and thank you!

[pfapin05]

I went to check resistance through the input and output jack wires and there was some resistance there, and I also went to check out the resistance through the input and output wires to the pcb board and there was also resistance there. I made sure the switch was turned on as well.

[thermionix]

Loud pop then humming suggests a power supply related issue.  Can you post voltages?  Also, that 1458 looks...suspicious.

[Danich_ivanov]

I would start with replacing polirised caps. Looking at photos, it's all seems to be just hanging in there, and one of the caps is pretty close to the switch. Also the other thing is to wire the circuit directly to in/out without the switch, then you will know for sure whether switch is an issue or not.

[pfapin05]

Loud pop then humming suggests a power supply related issue.  Can you post voltages?  Also, that 1458 looks...suspicious.

I checked the voltage at the dc input jack and it was read 9 volts, what other points should I check for voltage? Sorry Im kind of new to this.

[pfapin05]

I would start with replacing polirised caps. Looking at photos, it's all seems to be just hanging in there, and one of the caps is pretty close to the switch. Also the other thing is to wire the circuit directly to in/out without the switch, then you will know for sure whether switch is an issue or not.

I really appreciate this advice. I am kind of new at this so if you would be patient with me and help explain how to wire the circuit directly to in/out without the switch I would be very appreciative!

[Danich_ivanov]

Sure. From what i can tell by looking at the photos, you need to connect wire going to left middle lug of the switch with the wire connected to the lower left lug, and it will be input, and then you need to the same thing with the wires on right side, middle wire to lower wire, with lower wire being the one going to the jack (long one), it will be output. Unless i'm wrong that's pretty much it.

[pfapin05]

Sure. From what i can tell by looking at the photos, you need to connect wire going to left middle lug of the switch with the wire connected to the lower left lug, and it will be input, and then you need to the same thing with the wires on right side, middle wire to lower wire, with lower wire being the one going to the jack (long one), it will be output. Unless i'm wrong that's pretty much it.

Good deal, I just tried it hooked up like that and the pedal turned on but still no sound. Damn, I was really hoping that it would be the switch.

[ElectricDruid]

If you haven't got an audio probe, just solder a wire to the tip connection of the output jack and then use that. It amounts to much the same thing, and it'll tell you whether you're getting signal to the PCB, and whether you're getting signal out of the PCB.

From what you've described, it does sound a bit like the switch has got crunched. If the switch is broken and shorting things to ground, the PCB might appear not to work, so you'd have to unsolder the switch and wire the PCB in/out wires direct to the jacks to be sure.

[thermionix]

Is that millennium bypass?  Is that what the extra little board is for?  Sorry, I haven't used that yet, so I'm not so familiar with it.

Anyway, for voltages, the pins on the opamp chip are a good start.  Just be sure not to short any together with your meter probe.  Looking at the top, start where the dot is, that's pin 1, then go counter clockwise around to pin 8.  You should have 0V on pin 4, 9V on pin 8, and roughly 4.5V on all the others.

[pfapin05]

Is that millennium bypass?  Is that what the extra little board is for?  Sorry, I haven't used that yet, so I'm not so familiar with it.

Anyway, for voltages, the pins on the opamp chip are a good start.  Just be sure not to short any together with your meter probe.  Looking at the top, start where the dot is, that's pin 1, then go counter clockwise around to pin 8.  You should have 0V on pin 4, 9V on pin 8, and roughly 4.5V on all the others.

I have no idea if it is millennium bypass or not, sorry... I was not the one who built it. So I check the pins with the positive or red lead on the meter probe, but where do I place the negative or black lead at?

[pfapin05]

Is that millennium bypass?  Is that what the extra little board is for?  Sorry, I haven't used that yet, so I'm not so familiar with it.

Anyway, for voltages, the pins on the opamp chip are a good start.  Just be sure not to short any together with your meter probe.  Looking at the top, start where the dot is, that's pin 1, then go counter clockwise around to pin 8.  You should have 0V on pin 4, 9V on pin 8, and roughly 4.5V on all the others.

Nevermind I found where to put the negative lead. There was 0v on pin 4, 9v on pin 8, and about 7.7-7.9v on all the others besides one pin that was at 5v. Is that normal or are those values out of range?

[Slowpoke101]

The effects board is Tonepad's take of the Tubescreamer. The small board is a millennium bypass unit.
Take the IC out and measure the voltages on the socket. Pin 8 should show about 9V, pin 4 should be 0V. Pins 3 and 5 should show very close to 4.5V. Pins 1, 2, 6 and 7 should show above 2V but below 5V. If these are close to your measurements then the IC has failed and should be replaced.
If the voltages on pins 3 and 5 are higher than what is expected then a bit more investigation is required.
Let us know how you go.

[pfapin05]

The effects board is Tonepad's take of the Tubescreamer. The small board is a millennium bypass unit.
Take the IC out and measure the voltages on the socket. Pin 8 should show about 9V, pin 4 should be 0V. Pins 3 and 5 should show very close to 4.5V. Pins 1, 2, 6 and 7 should show above 2V but below 5V. If these are close to your measurements then the IC has failed and should be replaced.
If the voltages on pins 3 and 5 are higher than what is expected then a bit more investigation is required.
Let us know how you go.

Thank you, I would have had no idea that it is safe to take out a component like that and run voltage through the pedal to check it out. I will get around to doing this later on today. Thanks!

[pfapin05]

The effects board is Tonepad's take of the Tubescreamer. The small board is a millennium bypass unit.
Take the IC out and measure the voltages on the socket. Pin 8 should show about 9V, pin 4 should be 0V. Pins 3 and 5 should show very close to 4.5V. Pins 1, 2, 6 and 7 should show above 2V but below 5V. If these are close to your measurements then the IC has failed and should be replaced.
If the voltages on pins 3 and 5 are higher than what is expected then a bit more investigation is required.
Let us know how you go.

Here are the results after removing the IC chip...

Pin 8 = 9.1V
Pin 4 = 0V
Pin 3 = 4.5V
Pin 5 = 4.5V
Pin 1 = 4.5V
Pin 2 = 4.3V
Pin 6 = 4.5V
Pin 7 = 4.5V

What is the next step? Should I replace the IC chip with the exact same IC chip that was removed? The cheapest I found was 5 of them on Amazon for $7... are these the ones I should buy?

https://www.amazon.com/TEXAS-INSTRUMENTS-MC1458P-OP-AMP-pieces/dp/B00LQQXRNO/ref=sr_1_1?ie=UTF8&qid=1537893684&sr=8-1&keywords=mc1458p

Thank you guys for your help so far!