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 Post subject: Analog Chorus, no effect
PostPosted: Sun Jun 25, 2017 12:18 pm 
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I just finished building my analog chorus pedal and I'm having some trouble. It works in bypass and the clean signal goes through just fine. When I switch the pedal on I get a little drop in bass frequencies but no chorus effect. The LED comes on and pulses with the setting of the rate control but that's it. No chorus effect at all. I set the trim pot by turning it until it distorts and then dialing it back until there's no distortion. I've checked all my solder connections and remelted all of them. I didn't see any bad or bridged joints. The board isn't grounding out on the pots. I found a thread in this forum from last year (viewtopic.php?f=20&t=53429&hilit=chorus+voltages) where a member (projie) was having the exact same problem and it turned out to be a bad IC4 MN3101. In that thread one of the moderators (asked the member to check a couple of things before determining that it was a bad IC. I followed that advice and checked the same things so I'm posting my findings here hoping someone can help because there are some discrepancies.

A moderator, Morgan, asked the member to check pins 3, 7 and 8 of MN3007. In my pedal I have a signal at pin 3 but no output at 7 or 8. This is the same result projie got.

Morgan then asked projie to check voltages on MN3007 and MN3101. Moderator, Stephen provided his readings from a working pedal and projie provided his findings. My own findings differ from both.

Here are my voltage readings:
MN3007
1 - 8.03
2 - 3.90
3 - 5.75
4 - 7.50
5 - 0
6 - 3.85
7 - 6.33
8 - 6.33

MN3101
1 - 8.05
2 - 3.85
3 - 0
4 - 3.89
5 - 0.33
6 - 7.58
7 - 2.64
8 - 7.48

Here are the reading projie provided:
IC2 MN3007

1.8.31
2.0
3.2.96
4.1.4 but continually decreasing
5.0
6.0
7.7.8
8.7.8

IC4 MN3101

1.8.35
2.0
3.0
4.0
5.0.68
6.0
7.7.25
8.0.7 but decreasing

And here are the reading Stephen provided of his working pedal:
3007
1- 8.53
2- 4.44
3- 4.35
4- .57
5- 0
6- 4.38
7- 4.35
8- 4.35

3101
1- 8.53
2- 4.38
3- 0
4- 4.44
5- .29
6- 7.48
7- 2.73
8- .57

So I'm getting the same general symptoms as projie (no chorus effect) but different results when checking the same voltages that idicated the cause of his problem, and some discrepancies from the readings off of the moderator's working pedal. I'm not sure where to go from here. Any help would be greatly appreciated.

Attachment:
BYOC Chorus 1.jpg
BYOC Chorus 1.jpg [ 336.47 KiB | Viewed 7695 times ]


Attachment:
BYOC Chorus 2.jpg
BYOC Chorus 2.jpg [ 495.99 KiB | Viewed 7695 times ]


Attachment:
BYOC Chorus 3.jpg
BYOC Chorus 3.jpg [ 428.62 KiB | Viewed 7695 times ]


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PostPosted: Sun Jun 25, 2017 12:21 pm 
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And two more shots of the PCB and components. IC4 MN3101 doesn't appear fully seated in the photo but I've tried removing and re-seating it several times and that's as far as it goes into the socket.


Attachments:
BYOC Chorus 5.jpg
BYOC Chorus 5.jpg [ 480.23 KiB | Viewed 7688 times ]
BYOC Chorus 4.jpg
BYOC Chorus 4.jpg [ 503.98 KiB | Viewed 7688 times ]
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PostPosted: Sun Jun 25, 2017 12:30 pm 
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Doing some further reading I found this recent thread (viewtopic.php?f=20&t=55171) from another member with the same problem. This member had the same discrepancies as me between his readings and Stephen's. He ended up replacing one of the ICs (not sure which one) and it worked. Is BYOC shipping out bad ICs? Which is the suspect IC in these cases? I just checked BYOC's store and they're out of stock of 3101s and they don't appear to stock 3007s at all (but they have them in their kits?).


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PostPosted: Mon Jun 26, 2017 12:16 pm 
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Nice job troubleshooting! Please request a new new BBD (MN3007) from BYOC.

The BBDs used in this kit are new old stock. BYOC does test them, however it appears that sometimes they get damaged during shipping or something.

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PostPosted: Mon Jun 26, 2017 9:50 pm 
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Thanks for the confirmation. I'll let BYOC know about the issue and hopefully that can get another BBD in the mail for me quickly.


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PostPosted: Wed Jun 28, 2017 3:04 pm 
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I received a new MN3007 today and swapped it with the one that came in the kit. No change. Still no effect. This is super frustrating. I have a new MN3101 on the way. Hopefully that will fix it. :cry:


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PostPosted: Mon Jul 03, 2017 11:11 pm 
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I have replaced both the MN3101 and MN3007 and I'm still not getting a chorus effect. I checked voltages at every pin of both chips and it actually seems to be worse! My previous readings were:

MN3007
1 - 8.03
2 - 3.90
3 - 5.75
4 - 7.50
5 - 0
6 - 3.85
7 - 6.33
8 - 6.33

MN3101
1 - 8.05
2 - 3.85
3 - 0
4 - 3.89
5 - 0.33
6 - 7.58
7 - 2.64
8 - 7.48

The new readings after replacing both chips:

MN3007
1-8.28
2-0
3-1.96
4-0.45
5-0
6-0
7-7.04
8-6.98

MN3101
1-8.38
2-0
3-0
4-0
5-0.66
6-0
7-6.00
8-0.45

They are virtually identical to projie's readings that I referred to earlier in this thread, before he replaced his ICs:

IC2 MN3007

1.8.31
2.0
3.2.96
4.1.4 but continually decreasing
5.0
6.0
7.7.8
8.7.8

IC4 MN3101

1.8.35
2.0
3.0
4.0
5.0.68
6.0
7.7.25
8.0.7 but decreasing

He ended up replacing the MN3101 in his pedal and that fixed it but no luck for me. What the hell, man? My soldering looks good. I've triple checked every component to make sure they're installed correctly as well as all the wiring. I even checked for continuity between the solder joints of the IC sockets on the back of the board and every pin for both ICs. They're all good. I need help.


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PostPosted: Wed Jul 05, 2017 11:02 am 
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You should adjust the bias so that you have about 4.5v on pin 3 of the 3007. Have tested for signal on pin 3 yet?

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PostPosted: Wed Jul 05, 2017 11:26 am 
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byoc wrote:
You should adjust the bias so that you have about 4.5v on pin 3 of the 3007. Have tested for signal on pin 3 yet?


I set the bias to 4.5v on pin 3. No effect. I have a signal at pin 3.


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PostPosted: Wed Jul 05, 2017 2:46 pm 
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Check for signal at the BBD output as well - pins 7/8. If there is signal there, is it modulated?

Image

Image

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PostPosted: Wed Jul 05, 2017 5:23 pm 
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No signal at pins 7 or 8. I checked earlier when I was setting the bias and taking voltage readings. In case it's useful, here's the voltage readings from MN3007 and MN3101 after setting the bias:

MN3007
1-8.34
2-0
3-4.5
4-0.18
5-0
6-0
7-7.67
8-7.62

MN3101
1-8.35
2-0
3-0
4-0
5-0.66
6-0
7-7.57
8-0.23


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PostPosted: Thu Jul 06, 2017 10:13 am 
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Before moving on to some more tests, I need you to confirm a few things:

- What power supply are you using? What is your voltage at the striped end of D4?

- How are you testing signal?

- I've seen some builders intermittently flip the pin designation of ICs. This particular pedal can be a little confusing with the way the BBD and clock chips are orientated on the PCB and how they a shown in the schematic. This usually happens with pins 5-8. Any chance you've flipped any of the pin designations when reporting your voltages?

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PostPosted: Thu Jul 06, 2017 10:26 am 
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The last round of voltage readings is definitely way off and you won;t get any wet signal through that chipset with those voltages.

Here are my main concerns:
- BBD input bias voltage (pin 3) and output bias voltage (pins 7/8). These should both be close to 4.5 volts. They are effected by the trim pot. When you dialed in 4.5 volts on pin 3, your output voltage on 7/8 raised to over 7 volts. That's no good.

- Clock pin 7 is the LFO input voltage. This is typically below 3 volts and you are showing over 7 volts. When you first reported your voltages you had less than 3 volts there. If you reinstall the original clock chip does that reading come back down to <3 volts? Is the depth knob at the same spot for both readings? Or does that reading go back down if your turn down the depth knob?

- Interconnected pins: BBD pin 2 connects to clock pin 4 (A), BBD 6 to clock p2 (B), and BBD p4 to clock p8 (C). Your C voltage is okay, but A and B should be over 4 volts and you have nothing there.

See what the voltages do when you reinstall the original clock chip. Try various combinations of the two chipsets that you have to see how close you can get to Stephen's voltages. Once you get as close as you can, listen to the BBD output pins (7/8) while you slowly turn the trim pot to see if you can get any signal through the BBD.

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PostPosted: Thu Jul 06, 2017 10:50 am 
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The clock voltages seem way off. Your old clock voltage were better. Try putting the previous 3101 in and keeping the new 3007.

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PostPosted: Thu Jul 06, 2017 10:52 am 
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byoc wrote:
The clock voltages seem way off. Your old clock voltage were better. Try putting the previous 3101 in and keeping the new 3007.


....like what Morgan just said.

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PostPosted: Thu Jul 06, 2017 11:53 pm 
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"What power supply are you using? What is your voltage at the striped end of D4?"
- I'm using a Voodoo Lab Pedal Power 2 Plus. Voltage at the striped end of D4 is 8.58v.

"How are you testing signal?"
- I'm using my BYOC signal tester, my guitar, and amp. I don't own a signal generator or a scope.

"Any chance you've flipped any of the pin designations when reporting your voltages?"
- Here's how I'm taking notes every time I measure voltages:

Attachment:
BYOC Chorus 6.jpg
BYOC Chorus 6.jpg [ 64.2 KiB | Viewed 7534 times ]


"Clock pin 7 is the LFO input voltage. This is typically below 3 volts and you are showing over 7 volts. When you first reported your voltages you had less than 3 volts there. If you reinstall the original clock chip does that reading come back down to <3 volts? Is the depth knob at the same spot for both readings? Or does that reading go back down if your turn down the depth knob?"
- I reinstalled the clock chip supplied with the kit and the voltage at pin 7 dropped to 2.8v. The depth knob was the same for both readings but for good measure I checked to see if turning the depth knob changes that voltage and it does not.

"See what the voltages do when you reinstall the original clock chip. Try various combinations of the two chipsets that you have to see how close you can get to Stephen's voltages."
-The only combination of chips I had not yet tried was the replacement MN3101 with the original MN3007. It didn't fix the problem and my voltage readings were closer to Stephen's with the combination of the original MN3101 and replacement MN3007. This is the combination described with the voltage readings in the photo. Just in case it's hard to read my writing here's the voltages:

MN 3007
1-8.28
2-4.02
3-4.58
4-7.74
5-0
6-4.02
7-6.86
8-6.83

MN3101
1-8.40
2-4.05
3-0
4-4.10
5-0.39
6-8.05
7-2.81
8-7.92

"Once you get as close as you can, listen to the BBD output pins (7/8) while you slowly turn the trim pot to see if you can get any signal through the BBD."
- I found that when I set pin 3 on the BBD to 3.62v I do get a signal at pins 7 & 8. It's very distorted (buzzy, farty) but I do hear modulation in the signal and it changes with depth and rate adjustments. When I remove the signal tester and pug the output straight into my amp the distortion mostly goes away but so does the modulation. Even with the rate and depth turned all the way up the effect on my guitar signal is so subtle it's almost imperceptible.


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PostPosted: Fri Jul 07, 2017 10:22 am 
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Voltages look pretty good. 7/8 on the 3007 look a little high though. I'm really sorry to do this to you again, but can you contact sales@buildyourownclone.com and request a new set of chips. I'll personally make sure they are triple checked and all ESD precautions are taken when packaging.

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PostPosted: Fri Jul 07, 2017 11:11 am 
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byoc wrote:
Voltages look pretty good. 7/8 on the 3007 look a little high though. I'm really sorry to do this to you again, but can you contact sales@buildyourownclone.com and request a new set of chips. I'll personally make sure they are triple checked and all ESD precautions are taken when packaging.


I just sent an email. Thanks for the help. You're all awesome!


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PostPosted: Fri Jul 07, 2017 5:52 pm 
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Just as an FYI, I assembled my Analog Chorus kit earlier this week, and had the same problem: no effect when switched on. After reflowing all the solder joints 2-3 times I went and bought an oscilloscope, and found the same issue as on this and the other thread. The voltages on pin 8 of the 3101 and pin 4 of the 3007 were way too high (around 7.5 instead of around 0.5 as in Stephen's reference measurements).

The sales department sent me a new set of chips, which arrived today. I swapped them in, and the voltages on those two pins now read around 0.5. And I have chorus sound.

I hope you're able to solve the problem in your pedal. Your detailed posts here definitely helped me to solve mine.


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PostPosted: Mon Jul 10, 2017 11:22 pm 
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I received the new chips today, installed them, and....IT WORKS! And it sounds spectacular! Thank you so much for all the help with this pedal. You all are amazing!


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