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The pedal seems to work perfectly (bypass works, light turns on, sounds right, knobs work fine) but the volume increases a lot when the pedal is on. This happens no matter how much the chorus effect is mixed in (video shows it fully dry), and no matter which power source.
https://www.youtube.com/watch?v=66U_GLZc0Lc
This is my first pedal project and first time soldering a bunch of tiny components, so I'm kind of surprised I even got this far.
Anyway, it's probably messier than it should be, but I didn't see anything that could be causing a short. I'm guessing I put in the wrong resistor somewhere. I think I have a multimeter, if that helps. One mistake I know I made is installing some of the chip sockets backwards. I still installed the chips themselves in the right direction.
Photos:
https://imgur.com/a/2OoMs4W
Any help is appreciated, thanks!

Just want to confirm something: Is it your sense that with the effect switched IN, there is a volume boost but in bypass it is at the expected volume; or is it your sense that with the effect switched IN, the volume is at the expected level, but in bypass the volume has been decreased?

Also: do you have anything else in the signal chain besides guitar -> good cable -> Bass Chorus -> good cable -> amplifier ?

I have tried to check, based on the photos you provided, the most obvious resistor placements that would have an effect on the gain at each of the two op-amps in the signal chain (the two op-amps of the 4558) but I did not find an error. (That is, R4 through R8, and R22 through R25.) (All I can do of course is try to read the colored bands, and some codes are ambiguous.) A bad capacitor would be a wildcard here, but I can't check that ...

The volume without the pedal in the chain is the same as the volume with the pedal bypassed. Definitely boosted when the effect is on.
Nothing else in the signal chain, and the cables work fine otherwise.
If a capacitor could be the problem, how would I check that?
Thanks!

At some point here a multimeter may indeed be useful, so I don't think it would be a poor use of time to make sure you know how to use it to test for continuity, to measure resistances, and to measure DC voltages. If it can also measure capacitances, that would be good to know, though not necessarily easy to take advantage of. Likewise with measuring AC voltages--potentially useful in a case like this but not necessarily easy to take advantage of.

You may wish to go through and do a visual check, as best you can, of the capacitor values and resistance values of the soldered-in components; and look for solder bridges between pads where there should not be any; and *gently* prod solder joints to make sure they seem mechanically sound. On the topic of soldering, a whole host of maladies, great and small, can be caused by ok-looking but in fact inferior solder joints, so you might consider doing a "reflow" of the PCB. Here's a link to BYOC board moderator duhvoodooman's description of the process:

http://www.byocelectronics.com/board/viewtopic.php?f=9&t=52188

Given your description of the problem, I was looking for a simple explanation in terms of wrong resistances at the 4558 op amps (and didn't find any, but maybe you will). But another possibility may be, for example, if capacitor C3 per the schematic is poor (passes too much current) or is shorted out, I think that would cause a volume boost early in the signal chain. I consider this to be a long shot, but who knows. Anyway, here is a link to a page that includes the PCB map for the Bass Chorus, so you can see where on the PCB to find capacitor C3 or other components we may end up referring to here.

http://www.byocelectronics.com/board/download/file.php?id=5734&sid=f73f8ff06828496d7d067b5ce92b7881

But that case may be easy to test for--let us know how comfortable you are using your multimeter.


(In this case, with the pedal apparently doing almost everything correctly but us wanting to find out just where it is going wrong, it would be great if you had a simple "signal tester" but my guess is that you don't. Nonetheless if you can scare up an extra capacitor somewhere we may be able to help you cobble together the equivalent functionality, should it come to that.)

Have you looked at this post which concerned the same symptoms?

viewtopic.php?f=20&t=60301

Similar symptoms don't equate to the same cause, but it's something to check.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

One thing I would definitely check would be all of your resistor placements. Positional "swaps" of similar resistors--like a 100 ohm resistor where a 100K should be, and visa-versa--can cause the kind of behavior you've described. You'll need to do this visually by reading the color code bands, since resistors can't be reliably measured with a multimeter once installed in a circuit, due to the very common occurrence of parallel circuit paths. Get the PCB under strong lighting to help distinguish similar colors, and use a magnifying device.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

Checked all of the resistors and capacitors, and everything looks fine. I did notice that the 33k resistors I have are Orange/Orange/Black/Red/Brown instead of Orange/Orange/Brown/Red/Brown like in the instructions. From some searching it looks like those are still the right components, but I thought I should point it out anyway just in case it matters. I only got Orange/Orange/Black/Red/Brown resistors, no Orange/Orange/Brown/Red/Brown.





I noticed these two bridges, but I wasn't sure if those are supposed to be there. Apart from these two I didnt see anything else that looked like they were shorting.





Tried this, but unfortunately it didn't seem to make any difference.



Checked that one closely and still didn't see anything that looked wrong.



Pretty sure I don't have any extra capacitors laying around but I can look for one!



I did read that, but didn't actually manage to comprehend it until now. Between both 6/7 and 1/2 I'm getting readings of 47K, which, if I'm reading that post correctly, is wrong but different from the other person with the same problem.

That's a misprint in the parts list in the instructions--orange/orange/back/red/brown is the correct color code for a 33 Kohm resistor. The coding is explained here: http://byocelectronics.com/resistorcodes.pdf

I'll check out the two solder bridges as soon as I can--too late tonight.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

I think those two solder bridges may be redundant with traces on the PCB and therefore would not be a problem. It looks like they are at the two ends of R23, and reflect the connection of R23 to R24 in one case, and R23 to one "end" of the BLEND pot in the other.

You could consider trimming back that long tail of the wire that goes through the OUT pad (as seen in the same photo that shows the solder bridges). That's an invitation to a short, though I can't say that it is a problem quite yet.

At the risk of offending someone with my blatant expression of Yankee frugality, I'll point out that one place to look for such things could be circuit boards of electronic devices that are otherwise headed for the landfill. You can, at the same time, get some practice de-soldering, and also harvest some useful components (though typically they will have very short leads; you may need to solder some spare hookup wire on there).

Yes, those components are connected on the PCB, so no worries with the apparent solder bridging.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

I found a broken handheld tape player with plenty of capacitors. What would this "signal tester" do and how would it help, what kind of capacitor does it need, and what other components are necessary?

You can think of a signal tester as a "movable output jack." It allows you to connect any point in the circuit to your amp or other output device and hear the audio signal that's present at that point. The function of the capacitor is to block any DC voltage present at the test point and give a clean audio (AC) signal. Though it hasn't been in stock at BYOC for ages, they used to sell a signal tester, and you can see the instructions here: http://byocelectronics.com/signaltesterinstructions.pdf And it's very easy to make one from little more than an old instrument cable and a capacitor of ~10nf or greater capacitance.

To use it, connect your guitar (or other audio source) to the input jack of the pedal and connect your power source, but do NOT connect your amp/output device to the output jack. Instead, connect that cable to the 1/4" jack of the signal tester. Next, you want to affix the alligator clip of the tester to a ground point on the pedal--I usually use the sleeve solder tab of the input jack for this purpose. Be sure that you have a good, firm connection with the alligator clip, since the tester won't work if the black wire isn't grounded. Be sure your amp/output device is powered and set to go and engage the pedal footswitch.

To test, you need to hold the red probe of the tester against whatever point in the circuit that you wish to test for the presence of audio signal and then pluck one of your guitar's strings. What we want to focus on is the main signal path through the pedal circuit, which you determine from the pedal circuit schematic. The positions of the components to be tested are then found on a labeled PCB diagram, assuming that one is available. Check the pedal type forum index for a "PCB Layouts" thread. If it's not Available for that pedal, you can still identify many useful test points from the circuit schematic. What you're looking for is the point in the circuit at which the output drops out. The problem will lie between that point and the last point in the circuit where an audio signal was present.

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

What duhvoodooman outlines in the post just above would be the ideal way to proceed. However, there's another, low-rent way to go about it that I have described and illustrated in a set of posts just now, which you may wish to consider if you've managed to track down an appropriate capacitor but no other parts.

It starts here:

https://www.byocelectronics.com/board/viewtopic.php?f=8&t=60300#p505190

Alright, I think I found approximately where the problem is, but I don't understand the schematic enough to figure it out exactly.

When testing R5, the sound is at a normal volume. When testing R6, it is loud.
Pin 1 of IC1 is loud.

I don't see any shorts on those resistors or on the IC socket. Both resistors seem to be the correct ones as well. Is there something specifically I should test in that area to see what the exact problem is?

Is this the same thing as saying "The signal at pin 1 of the 4558 is a lot louder than the signal at pin 2 of the 4558" ?

To ask this another way, can you say which ends of R5 and R6 you were testing? You may need to answer in terms of the PCB map since that describes how you access the circuit; the schematic diagram is not printed on the PCB! (Recall that in an earlier post I gave a link to the PCB map.) From the point of view of the circuit theory, it's necessary to know which end is which on the schematic as well, but we can eventually work that out. (Since I have this same pedal, I can do direct comparisons if need be.)

It still seems to me that the behavior could be explained by there being a short across, or failure in, C3, but I've been trying to think of a definitive test for this without needing to do more surgery on the circuit, without success.

Measuring resistances in a circuit is problematic, for various reasons; I think duhvoodooman may have mentioned this in an earlier post in this discussion. Nonetheless, you might try to see what resistance reading you get for R4. The schematic says 47k and I presume the color bands do as well, but if the reading actually comes up significantly lower, then that may explain the unwanted volume gain at that location in the circuit, and would make me seriously start to suspect C3. The C3-R5 series combination is in parallel with R4; a DC resistance measurement, assuming a non-faulty C3, would just yield the R4 resistance, but a shorted out C3 would mean a parallel combination of R4 and R5, probably 8k or so, and accounting for the unexpected volume gain. This is still speculative, but best I can think of at the moment.

That IC1A op amp circuit is a moderate gain stage, so what you describe sounds normal to me.

I think I'd be looking (or signal probing) around the blend control and the IC1B final gain stage. Have you determined if the high volume is coming from the clean signal, the processed signal, or both? You can check this by adjusting the Blend control through its sweep. Loudest at the start (full CCW) and decreases as it's dialed up, quietest at the start and increases, or the volume doesn't change noticeably across the sweep?

_________________
“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

Yes, the signal at pin 2 is a lot quieter than the signal at pin 1



Looking at the PCB map, the top end of R6 is much louder than the bottom end of R6 and both ends of R5. It is much louder than both ends of C3 too, if that means anything.



4.67K



The processed signal seems slightly louder than the clean signal, but both are significantly louder than the bypassed signal and the signal with no pedal.



Here's a few things I'm hearing around there, not sure what's relevant and/or unusual:
The bottom of R23 is significantly louder than the top of R23, similar to the final output volume. Same thing for C13.
R8 is about equally quiet on both ends.
R24 is significantly louder on the top than on the bottom.
C12 and R22 are loud on both ends, similar to the final output volume.
Pin 7 of the 4558 is similar to the final output volume.

I think that may be the problem; having 4.7k leads to a signal boost of up to x10 w/r to what was intended. Mine says 46.8k, which is what one would expect from the schematic with a non-faulty C3 and no parallel-resistance-paths difficulties of measurement. That resistor is buried between two tall caps on the PCB and as a result it's too difficult to check it from your photos--and I had trouble reading my own copy, in real life. In fact I had trouble getting my multimeter probes in there. There is an excellent chance that this is a case of what duhvoodooman described in an earlier post:



It may be that your kit came with one 4.7k too many and one 47k too few, but an inadvertent swapping of *two* R's is what I would look into next.


edit to add: R38, which is near Q5 and C17, looks like it could be 47k in your photos, but is supposed to be 4.7k. Presumably an error that large in that resistor (R38) would have some effect on the character of the chorus sound. To the extent that you have explored the pedal controls, does the chorus quality seem to be what you expected?

Sorry, I meant to type 46.7k! Pretty sure that's what the multimeter read. I'll check it again tomorrow though, just to make sure

Ha, ok, well if that's the case then my previous post may be pretty worthless. I will contemplate the other observations you made.

I've now had a chance to repeat some of what you have done, on my own Bass Chorus.

First of all I have essentially the same signal level at several key points through the circuit, including the input jack tip lug, pin 1 of the 4558, pin 3 of the 3207, pins 7/8 of the 3207, and pin 7 of the 4558. The color of the sound differs at different points because there is significant filtering going on, but the overall level does not show any significant variation. If I wanted to try some more points, I would choose the emitters of transistors Q1, Q2, and Q3, but I am sure that in my pedal it would still sound the same volume.



Note that R23 and R8 play the same roles as each other, the former for the wet signal and the latter for the dry. I suspect your results there were found when you had the BLEND knob fully clockwise (CW). With my pedal, the "top" of R23 and the "right end" of R8 are always "quiet." With the BLEND knob at noon, the "bottom" of R23 and the "left end" of R8 both show strong signal, though not as loud as the points mentioned in my first long paragraph above. Turning the BLEND knob fully CW or fully CCW tapers one or the other of the "live" ends ("bottom" of R23; "left" of R8) down to zero. There is a lot of symmetry to what it is doing, as you well would expect from the concept of "blend"--even if you can't see from the schematic diagram how it works. I still suspect there is something amiss further upstream, but I think it would be worthwhile for you to repeat these R8/R23 measurements for several BLEND knob positions (CCW, CW, and noon) to see if you get the kind of behavior I have described here. If not, then there could be some issues at this downstream end.



That's good! Pin 7 is essentially the pedal output.

For me, the input is at a normal volume but the rest of those points are equally significantly louder than the input jack tip lug. Following the signal path from the input, the first place I hear a significant gain increase compared to the input is when testing the top end of R6 (and pin 1 of the 4558 is the same volume as the top end of R6). It's definitely much louder than the input, and sounds quieter than the output. Of course I don't know much about how this works, but from looking at the schematic and knowing that your pedal didn't have the gain increase after pin 1 of the 4558, I still suspect the issue is somewhere in that area.



Yes, that seems to be working as intended (and makes more sense knowing what they actually do).




Going back to check R4 with the multimeter again, it actually did say 4.67k! It's very clearly yellow/purple/black/red/brown (47k), but I'm not getting 47k. R38 read -4.4k, but is also definitely yellow/purple/black/red/brown (47k). Maybe R4 and R38 are both 4.7k labeled as 47k? Would it be most helpful to just desolder both and measure them using a multimeter away from the PCB?

Executive summary: I believe that at the very least you need to replace your R4 with a 47k resistor.

Chattier version:

Colored bands are well and good, but the electrons don't know what they are. What really matters is the actual resistance--that's why many of us take the time to check all resistances at the very start of the project. I sort them into bins according to the measured resistances (I have a fine collection of fishing lure boxes to help me). In fact, I have trouble reading a lot of the bands anyway, so I find it necessary. The younger may not!

If your R4 is actually 4.7k I think that will completely explain your problem. That means you have an unwanted gain boost pretty much at the start of the signal massaging, and it persists throughout the circuit, as you have discovered. You would need in that case to replace it with a 47k resistor to get back to the design, stock specifications. I don't know whether your R38 is 4.7k or 47k; again, we can scrutinize the colored bands all we like, but the actual resistance is what matters. I have just prodded my own Bass Chorus again, and measuring R38 in place I get 4.6k. So if yours read 4.4k, then probably it is in fact nominally 4.7k (which is what it is supposed to be).

De-soldering them and measuring them in isolation is a way to be sure, but is a bit of a hassle. It *would* be good to know whether you simply got a 4.7k in place of a 47k, or whether you accidentally made a swap of the real R4 (47k) with one of the 4.7k resistors--R15, R37, or R38. From your photos it seemed to me that R38 was a real possibility, which is why I suggested it. You might try measuring R15 and R37, just to be sure. If either of them turns out to be 47k, the perhaps the mystery is completely solved (and then it will be time to de-solder, swap, and re-solder). R15 is difficult to get to from the component side, but I do find 4.7k or 4.6k for all three, so these seem to be cases where measuring in place works ok.

All of those were 4.7k for me too, so it's probably just R4 that's the problem. I desoldered it and measured the resistance again just in case - still 4.7k. I'll get the correct 47k resistor, put it in, and I'll report back here in however long it takes to get it!
Thank you so much for all the help with this, and I'm hoping this will be the end of my problems. I really appreciate all the time and thought put into this from everyone who helped!