Hey all:
Looking for some tips on how you typically go about troubleshooting pedals. I'm testing out a board I built out on a test box and something is way off. Originally, I wasn't getting any signal at all, so I triple checked I'm following the layout and found some spots with some sloppy solder work that was connecting rows incorrectly. Now I'm getting a signal, but it's crackly as all hell and the dynamics are all over the place. One second it's quiet and the next it's piercingly loud. Any advice on how to get this resolved apart from me throwing my tools in the ocean?
Thanks,
George
With strip board. Run a knife down all the tracks. Check voltage with a DMM then audio probe. You should be able to track the audio pretty easily, just follow the components.
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Got it, thanks. What am I looking for when I'm checking for voltage? Is there a primer somewhere on how to check for voltage?
I checked out a few videos on how to get voltage readings, so think I get the rough gist of it. I've got a very cheap DMM. What setting should I be on to read the 9V battery?
If I'm looking at it right, the top left 20 should be fine.
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Cool, cool. Thanks.
I'm not getting any voltage reading on the input, so I guess that's a good place to start!
What's the cause of getting an incorrect reading. Bad soldering job?
The guy who has the diygp shop (linked above) has a really good video about making and using an audio probe. Dead simple, no solder needed.
The basic idea is that you use a probe to directly play some recorded sound through different parts of the audio path of the circuit. By connecting the audio out to the leg of a resistor or capacitor or whatever is would normally have the guitar signal going through you can isolate where the problem happens. It's usually easiest to start at the out put of the circuit and work your way backwards to the input.
Oh, nice. Thanks.
I don't see the link to that video -- could you share?
https://m.youtube.com/watch?v=jWvIfDSxbIk
That's for an audio probe, which is super helpful too. For voltages, the red probe goes to different point o. The board, the black goes to ground. I usually use the power supply ground.
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Don't forget at first to controll the consistency of all tracks at PCB. Crackles in tracks or around soldered points. At your DMM use conductivity function. That diode/beep at cca 5. hour.
Nice. Thanks for the video -- super helpful.
And thanks for the tip on going to ground on the power supply -- I was able to finally get a reading when I figured that out.
@Zerro what do you mean about "controlling the consistency"? I've was able to find a few solder bridges using the conductivity function, but not sure how to check for consistency.
Also: I finally have a signal! But there's no sustain on the signal, especially if I crank up the fuzz pot. Here's a recording. Any one experience with this? What causes this kind of dead tone?
https://drive.google.com/file/d/1yNvYY2IX5-uaZAH7gWclpZFkBY4uqjOR/view?usp=sharing
Hi, I meant if that tracks and soldered points are not interrupted, and/or damaged by etching or soldering. Sorry for my english, it's not my native language.
Ah, got it. Makes sense. Thanks for clarifying!
Anyone got any tips on dealing with a signal that's crackly/decays too fast?
Here's the sample audio again: https://drive.google.com/file/d/1yNvYY2IX5-uaZAH7gWclpZFkBY4uqjOR/view?usp=sharing
Resistor R5 in collector of first transistor 100k - it serves as Gate function. Try play around it, to get at collector of second transisitor cca 5-7 Volts DC. That's my tip.
Try to sent info what is that machine - type and name, or better, schematics. To help us to consider it. Now I only guess. Generally, as I said, if it is some 2 or more stages transistor fuzz, resistor in collector of first transistor, going from power line, can be too high. Try to set it with trimmer.
I'm in the home stretch troubleshooting this pedal. The circuit works, and now I'm running into a few problems loading into the box. Some thoughts on what's going wrong:
1. Pots: Should the bottoms of the pots be connected to ground when I continuity check? I'm worried the way I installed them is shorting the circuit. Any tips on best practices for
2. Circuit: Could the board itself be shorting? I've put a pad of foam underneath the board to make sure it's not coming into contact with the DC jack, LED, enclosure etc. but maybe that's not doing the trick?
Thanks,
George
Too few of infos about your project. Send schematics, close photos etc... Everything can be mend. Just we cannot only guess.
Pots should be wired up as per the schematic. This isn't a the control cavity of a guitar, you don't solder the backs of pots together here. If anything you cover the backs of pots with non-conductive material to keep them from shorting out the board. Speaking of which...
Yes, you can short the board but it's fairly easy to prevent this with standoffs, some non-conductive material between the board and the enclosure and other components within it.
I use pizza-box "tables" with the legs cut off and hot-glue them to the enclosure if the board is free-floating — but I prefer board-mounted switches and pots to prevent movement/free-floating.
As for crackle... Zvex said "Crackle Ok" therefore it must be so...
Got it. Thanks. I realized I wired up the DC jack incorrectly, which was why I wasn't getting any power to the circuit. So, one step down.
Now I have a fresh bug to figure out. I'm getting a signal, but it's very faint. Basically, I have to crank up my amp all the way to eleven to get any sound, and even then it's not that loud.
What could be the issue here? I tested the circuit before wiring up the enclosure and it sounded fine. So, it's got to be an issue with how I wired up the switch/jacks/LED.
I don't have the schematic, but here's the layout:
http://tagboardeffects.blogspot.com/2015/12/lovetone-big-cheese.html
And here are some photos of the enclosure (not pretty, I know).
Thanks for tolerating all the newb questions, everyone.
Thanks,
George
My questions - I attached schematic of Big Cheese, I found at web. Is it that machine, you are building?
You mentioned, that you had issue with power connector. Did you only connected it at wrong place (and where?), or you changed wires to PCB? It would mean, that both transistors and op amp got reverted polarity. This will damage them for 95%. There is big rotary switch; by my opinion, here is many times problem - wrong wiring.
- So, get off transistors and opamp and measure them with some multimeter, or exchange. This is I would start with.
- Make measure at red points I made in schematic, if it is that schematic you build of course.
- Control that switch
Thanks for sending this over. Yes, I think this is roughly the same schematic, although I'm using BC549 transistors.
I made a pretty dumb mistake and hooked the 9V+ lede to the LED and the LED lede to the + tab on the DC jack. Basically, flipped where the 9V+ and LED ledes were supposed to go here (http://tagboardeffects.blogspot.com/2015/12/lovetone-big-cheese.html). I guess that could have fried the transistors and IC?
Thanks for highlighting the places to measure, super helpful. What measurement should I be getting at those points? Am I looking for a 9V reading on the multimeter?
Also, how do I control the switch?
Thanks again,
George
Hi, I am affraid I don't fully understand what you did with those "lede"s. But never mind. Now you only controll those measure points, what DC voltages will be there (you will find maximally 9V). Switch controll only to verify that all contacts are ok, at the proper pins.
Quote from: GeorgeFormanGrill on May 24, 2021, 12:28:53 AM
...
I made a pretty dumb mistake and hooked the 9V+ lede to the LED and the LED lede to the + tab on the DC jack. Basically, flipped where the 9V+ and LED ledes were supposed to go here (http://tagboardeffects.blogspot.com/2015/12/lovetone-big-cheese.html). I guess that could have fried the transistors and IC?
...
That won't have fried the transistors & IC. If your trace-cuts are correct all you did was send the power to the IC etc through the CLR, a reduction in voltage is all — what's intentionally done on some pedals and called "Sag" or "Starve" or "Stab" (latter as in stability).
The LED was still getting reduced voltage through the CLR as well, so it didn't pop — LEDs aren't fussy about which side of the equation you limit the juice, but you do have to limit it somewhere along the line. The LED would've popped if you'd fed it a full 9v, though.
Maybe try going through the build beginning to end again; pretend you're starting from scratch and check each component is the correct value as you "place it", and oriented correctly as well. As you go, check for cold solder-joints and re-flow anything suspect.
After that, do the same for each wire while comparing it to the schematic.
It may help to leave it for a few days, re-approach with a "fresh" set of eyes. Numerous times I've done so and saw a mistake that previously while in the moment I kept not-seeing every time I looked over the build.
Any idea on this MXR rebuild. using an audio probe, everything to the left of the red line with the exception of the (4) 47nj100's with the purple X on them gives me sound when the phaser button is engaged. Also the (2) lugs on each chip with red circles on them. I do have normal sound from my guitar when the phaser is in off position.
So should there be sound off anything to the right of the red line? Thanks in advance.
What happened before it stopped working?
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I disconnected R26. I was going to put a switch to cut & add it. But now it doesn't work with it connected or not. Geuss I gotta hit all joints to eliminate a cold spot??
That's a good start, is that an MXR board or where sis it come from?
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It's an aftermarket from https://store.generalguitargadgets.com/collections/kits/Phase-Shifters
Quote from: mgalicki on June 05, 2021, 09:17:00 PM
It's an aftermarket from https://store.generalguitargadgets.com/collections/kits/Phase-Shifters
Just from reading the instructions:
There is an R15 resistor that is in some of the later Phase 90's. It is shown in the schematic, but is not shown in the layout because it is not in the Script version. There is a place for it, so you can add it. We added it in the one pictured below so you can see where it would be. It works either way.
Why did you choose R26? We are going to need to close picks of both sides too. Reflowing your joints is a great start.
See pics attached, I did the R26 cause I thought that's what several mod instructions said to do. My bad, it's the R28..
I was just curious, sometimes it helps to know why. Did you get it working?
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Still not working, I don't get it? This board is tight in the case though, I may have damaged a component. I ordered a signal tracer / injector pen to test all the components. I'll let you know what I come up with when I get it. Thanks for all your help Jimilee!