- This topic has 13 replies, 1 voice, and was last updated 2 years, 8 months ago by
.
-
Posts
-
So I built the Quaverato, everything works, leds light up, tap works, all knobs and switches do what they should. However, the volume only works when turned up all the way, and even then its very low and not at unity. Turning the volume anywhere less than about 3 o’clock and there is no sound. I’ve adjusted the gain trim to no avail (even turning it 50+ turns either way). I’ve taken the pedal apart and re-flowed all solder joints twice now. Re-flowing both times yielded no significant results either time.
Andy,
Sorry about this trouble.
Your idea to re-flow the solder joints was good. That would have been my first guess. I know that the problem has to be somewhere in the analog signal path…it could be anywhere from the beginning of the circuit to the output.
Does the signal sound fine through the pedal when it is bypassed (when the red led by the bypass footswitch is off)?
What are the results of your tests of step 6 in the troubleshooting guide?
-Brach
Thanks for the quick response!
1) Yes, signal sounds fine when pedal is in bypassed. When engaged, everything works, the volume is just very low.
2) Referring to the Troubleshooting Guide:
#6: Yes, signal flows fine with Depth knob fully counter clockwise
#7: Yes, tremelo effect works with bypass on and Depth knob fully clockwise
#8: Yes, audio seems right, the volume is just too low to really hear it.
3) When engaged, sound does not seem distorted
4) Tapping or banging the pedal results with no clicks or breaks in sound to suggest a loose connection
5) Gain trim pot set at 40k results in almost no sound, lowering it cuts it out completely, if I ramp it up all the way to around 95k it does get a little volume boost above the 40k range, but not by much.
6) Double-checked to make sure I didn’t switch the Jfet with any other transistors.
7) Double-checked all solder joints for bridges or poor solderingAny ideas would be greatly appreciated!
By the way, I really dig this kit, it was awesome fun to put together!Since it’s not passing audio correctly, work through step 6, A-E to see if you notice anything wrong.
Let me know what you find.
-Brach
Okay – here’s where I’m at: Working through #6 everything was checking out until I started checking voltages on the IC. Several voltages were way off. I dont really know how the pins are labeled, so bear with me as I try and describe it. Most pins register about 4.2V unless otherwise noted. If you are looking straight down on the board (so the IC is upside down) – pins from left to right, top row: pin #3 reads 2V, pin #4 reads 8.32V. Bottom row, left to right (again, IC is upside down) pin #3 reads 4V, pin #4 reads 0V. Reading voltages at resistor R10: left side reads 4.04V, right side reads 8.33V, so I think that resistor is working. I went over all the parts listed in Appendix B (U2 Voltages) just in case. I cant see any bridging or bad joints, but after re-flowing the solder a bit earlier I may have burnt a pad. Anyways, since I don’t know what parts those pins affect, any guidance would be appreciated. I worked through the rest of #6 in the Troubleshooting manual as well. So I had re-done the jumpers too (that seems to be a common error part) and re-flowed some other joints as well. After testing, pedal still functions the same (everything works, but volume is still low).
Also – I don’t get a reading at R28, maybe thats the bad joint?
Your description of the pins is very confusing to me. The IC pins are numbered on the voltage chart on page 1 of the troubleshooting guide. It would be very helpful to me if you could list the pin number and then it’s voltage. It’s much easier if you just measure the pins from the top of the board (not the solder side). make sure to use a solid ground point for the black probe of your meter.
If you get 0V on R28, that’s a major problem. The red pad in the volage chart should be 5V. That could explain why you get very low output. Once again, please make sure that voltage reading is correct, with the black probe on a known, solid ground point.
It might be helpful if I could see your board and solder joints. If you could take some detailed, in focus photos of both sides of your board, with special attention shown to the solder joints (even under the pots), I might be able to see something that could be causing the issue.
-Brach
Ok, didn’t see the labeled pin diagram so hope this is better: all pins show 4.2V except Pin 5 shows 2V, Pin 4 shows 8.32V, Pin 10 shows 4V, and Pin 11 has 0V, these are readings off the pins themselves on the top of the board. I replaced R28 thinking that was the issue but it didn’t change anything, reading the pad shows about 0.05V. I took some photos, how do I upload them to this post?
Thanks for getting back to me about the voltages. The IC voltages are fine for now. I think your problem is with R28…or at least the lack of voltage there is the symptom of the problem. I want to focus on getting that fixed.
Sorry about the photo hosting issue. You have to upload your photos to an external site (like “google photos” or something) and then link to them here on the forum. I know it’s a pain, but this forum software makes us do it that way
-Brach
Sorry for the holdup, here’s a link for photos, let me know if you need more, Thanks!
https://photos.app.goo.gl/Cx5dXVopHHmPKiVZAThank you for the photos. Sorry it’s taken a few days to get back to you, i’ve been really busy.
I don’t see anything directly in the photos that I think could be the issue, but i do notice that a lot (maybe most) of the solder joints have about twice as much solder on them as they should have. Please try to re-flow the solder joints with a clean tip (without solder on it) to see if you can remove some of the solder from those joints, and to ensure that everything is making a good electrical connection. As an example of what i’m talking about, look at the solder joints of the relay, they look more spherical instead of the “concave conical” shape they should have. In fact, the joints on the relay could be causing this problem.
I couldn’t tell too well because some of the photos aren’t in great focus, but it kind of looks like there are little extraneous pieces of solder around the top of the circuit board. These need to be cleaned up because they will cause shorts. You can use your soldering iron to pick them up.
Can you please double check to see if R28 has close to 0V on it? If so, please re-flow the solder joints on the ISP pins, because R28 is connected to some of those pins, and they could be shorted or something. If that doesn’t work, then remove C17 to see if that makes a difference with the volume. Removing this cap will bypass all the signal muting circuitry, so you can see if that is causing the problem.
-Brach
Okay – So I went around the board and used some solder wick to clean up the large blobs (yeah, I know I added a lot of solder), and really clean it up, especially between solder points, and reflowed basically everything. This didn’t change anything and R28 was still reading 0v. So I took C17 out and the volume is definitely louder. If I turn the volume pot all the way up its at unity and sounds great, turning it down the volume gets really soft quickly. But, this is a huge improvement.
I’m not sure what’s going on with the voltage on R28. Please check pin 17 on the microcontroller for 5V (Google “pinout for atmega328p” if you don’t know where pin 17 is). Let me know what you find.
It’s not super vital that the silencing circuit works; it’s job it to help make the relay click quieter. So unless the sound of the relay click bothers you then you don’t need to worry about fixing it.
Is the gain trim pot set correctly? You should have more than just unity gain with the volume knob all the way up. You might want to play around with the gain pot setting to see if you can increase the volume. If turning it (all the way counterclockwise) doesn’t help, try gently wiggling the gain pot (while playing guitar through the pedal) to see if that makes the volume jump up to a louder level.
-Brach
Sorry for the delay – OK, so pin 17 reads 4.97V. I do notice the relay click, would be nice to fix it, but not the end of the world. Also, turning the gain trimmer up definitely boosted the volume, it gets above unity now, not a lot, but it is louder. Thanks for all your help!
