Build Your Own Clone Message Board

Hi Everyone,
I am building a pedal that combines the Stereo Flanger and the Bass Chorus in the same box with a pedal switcher. I drilled a custom case. I am having troubles with the Stereo Flanger side.

Background Information

Bypass on both side works
Bypass on both sides work with the order selector in any order (Stereo Flanger first or Bass Chorus first)
Bass Chorus side works fine in any order
When the Stereo Flanger is engaged, with or without the Bass Chorus and in any order, the signal pretty much disappears.

All of the pots are wires for both pedals and not directly connected to the PCB.

Troubleshooting thus far

I search the PCB, switches, and pots for short to ground. I did not notice any.
I did notice that one of the BBD chips isn't fitting properly into the chip socket. Perhaps this is the issue.
I also noticed a slight thumbing sound / faint ossilation when I turn the amp attached to the pedal up. I only notice this when the Stereo Flanger is engaged. I can also faintly hear the guitar when the amp is turned up.

I'm not sure if this is a bias issue. The bias pot says 15x on it.

Photos can be viewed at the following link. link
I would appreciate input.

Thank you,
Jon

I don't know much about this circuit, but there are two generalized pieces of advice I'd offer.

1. Any time you do a multi effect build, make sure that each effect works independently before trying to wire them and house them together. It doesn't seem like this is causing your problem, but it's always better to know for sure. This rule is similar to the "get it working stock before you mod it" rule.

2. You could clean up some of your wiring and soldering. Trim the wires back as close to the board (or solder lugs) as you can; exposed wires can cause shorts. And some of the soldering could be improved by reflowing the joints with a clean, hot iron tip. Probably best to remove the ICs when you do this.

Speaking of ICs, you mentioned one of the BBDs not seating correctly. Which chip is that? Have you tried carefully removing it and reinstalling it?

_________________
Scott

My band, Austin Hollow

Hi, thanks for the reply. The chip that isn't seating right is BBD A, it is an MN3207 chip.

I tried to remove it and straighten the pins, but I can't seem to get it to seat properly.

I attached a photo of the chip. It is the one on the right.

^^This^^

Your symptoms do not tell us if any signal is making it to the PCB, which means it could be a bypass switch issue. With the flanger circuit, you would get clean sound through the circuit even if one of the BBDs doesn't work or if you have an issue with the pots or switch or something. So don't worry about those components yet. Clean up your bypass switch PCB; clip those leads; make sure everything is connected correctly there (a photo of the actual switch and wires leading to the bypass PCB could be helpful), and make sure you don't have any shorts on those tiny solder connections on the switch PCB header.

If that doesn't help things out, you'll need a signal tester or audio probe and likely a DMM to trouble shoot.

_________________
MasterDelayer/Reverbrador/Ampaholic/TopJacker

I replaced the bypass switch and touched up all the semi-bad connections I could find. Still no luck. Time to start probing with an audio probe.

What are the diodes doing in this circuit? I don't understand the schematic at that point.

Thanks again for your help.

Hi Morgan,
To clarify, I am getting sound when the pedal is engaged, the sound is just very low in volume compared to bypassed volume. This is the same even after cleaning up and replacing the bypass switch.

Probe the dry signal path first to determine why the signal is so quiet in effect mode. here is the dry signal path:

R2 > IC1 pin7 > R25 > R27 (wet signal mixes between R25 & R27) > IC5 pin1 > R30

Find out where the signal gets cut and check out the associated components for that section of the circuit. Let us know what you find. If the signal is already quiet at R2, it is likely a switch issue.





http://byocelectronics.com/flangerscheme.pdf

And here is a chart showing relative voltages if you would like to compare voltages from your build:
http://byocelectronics.com/board/viewtopic.php?f=20&t=23517

_________________
MasterDelayer/Reverbrador/Ampaholic/TopJacker

Thanks. You wrote earlier that "When the Stereo Flanger is engaged, with or without the Bass Chorus and in any order, the signal pretty much disappears." I read that as the signal is cut. It's important to be as specific and clear as possible.

_________________
MasterDelayer/Reverbrador/Ampaholic/TopJacker

Hi Morgan,
I do not get any signal at any of the points you mention in the dry signal path nor the wet resistor. If I probe right on the mono output, I get great level.

Do you have any thoughts?

I found a bad joint on IC 1. I reflowed all the joints and everything seems to probe well as well as the center post on stand off board for the bypass switch.

Probing the center point leads to good signal as well. Plugging a guitar in, still leads to poor signal.

I'll try a few more things tomorrow.

Thanks for all the help I have received so far.

I probe all of the ICs. I am getting some really strange voltages on the DMM. Below are the voltages of the ICs. Your thoughts and assistance is greatly appreciated.

IC1
3.9
3.9
3.9
0
3.7
3.9
3.9
7.8

IC 2
0
2.3
2.7
OF
OF
2.2
2.6
2.6

IC3
0
2.2
2.7
2.6
4.6
2.3
2.6
2.6

IC4
7.1
7.1
7.1
0
.9
.6
7.3
7.8

IC5
7.2
6.2
7.1
0.0
7.1
7.1
7.0
7.85



IC6
2.5
2.5
2.3
0
2.5
2.5
2.5
5.0

IC7
5.0
2.2
0.0
2.3
4.7
320mv
4.0
4.6

IC 8
5.0
0
7.8

Attached is a photo of the regulator with part number.

Here is a link to a video of what is going on. I double checked all the transistor model numbers and positions and they appear to be correct. I removed the order switching mod and have a jack connected straight to the input.

https://drive.google.com/open?id=1p3u-D ... oSDfp4RqAq

I'm surprised the circuit is passing any signal at all with those voltages. IC5 and half of IC4 should be pretty much identical to IC1. This high bias voltages on pins 1-3 and 5-7 are causing signal issues. You should have right around 3.7 volts on those pins. Bias voltage for IC4 and IC5 comes from the junction of C31, R55, and R56. Check out those components for value and orientation, make sure there is no short between the legs of the electrolytic capacitor (happens quite often), resolder those connections. Keep working that area until you get <4 volts on IC4 pin 3 and IC5 pins 3 and 5. You should also remove those ICs from their sockets and measure right from the sockets in case one of the chips is shorted and throwing those voltages off.

Also, your BBD output voltages on pins 7 and 8 are a bit low. You'll want to fine tune the bias trimmer once you get full signal going through the pedal.

_________________
MasterDelayer/Reverbrador/Ampaholic/TopJacker

I found a bad 10k resistor last night, I replaced it and everything seems to be working. I’ll do more testing before putting it back together. Voltages seems correct after replacing the resistor.