# Cepheid Chorus no Sound



## Jarrett (Nov 30, 2021)

I just finished putting together this chorus pedal. I've done the Caesar already as well as a Small Clone clone, so I generally know what I'm doing with chorus pedals, but this time I have no sound when I engage the switch.

I have bypass signal, but evidently I have an open circuit somewhere. I also have no led's (edit: leds are working).

I was wondering... I subbed 3 of the 5088 transistors for 2n3904's because I read somewhere about this being okay in certian fuzz circuits. Could this be my problem? The rest of the build looks pretty clean compared to my usual work.

Edit... okay here are a couple pics. I had to chop them up to get them to upload... sorry about that. Also, thanks guys for the super quick responses!


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## Bobblybook (Nov 30, 2021)

Jarrett said:


> Ps. I tried to upload a photo, but I keep getting a message saying the file is too large for the server to process.


I guess resize it to a smaller resolution and try again, I'm not sure what the file limit is exactly.


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## Kroars (Nov 30, 2021)

Jarrett said:


> Ps. I tried to upload a photo, but I keep getting a message saying the file is too large for the server to process.


If you’re using an iPhone go to attach files, then photo library, select photo.  Before you select “Add” look at bottom of screen where it says “show selected” hit that.  Then the picture(s) will pop up and on the bottom right you’ll see “Actual Size” -hit that.  Then choose either small, medium or large.  Usually either of the three work, just not actual size.  If large doesn’t work, repeat steps and hit medium.


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## carlinb17 (Nov 30, 2021)

Why did you sub out three of the four 2N5088, the 2N3904 is a medium gain transistor while the 2N5088 is a higher gain one. Not sure if it matters in this build but just curious why. Pictures would definitely be needed to move forward though. Where did you source your BBD's?


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## fig (Nov 30, 2021)

No LED...That's right out of the power gate...I'd start by checking around the protection diode and switch.


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## Stickman393 (Nov 30, 2021)

+1 to figgy.  Check the orientation of your  1n5817.  If that's good, double check the polarity of your incoming voltage- center to negative, outer to positive.


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## fig (Nov 30, 2021)

Stickman393 said:


> +1 to figgy.  Check the orientation of your  1n5817.  If that's good, double check the polarity of your incoming voltage- center to negative, outer to positive.


I love it when you talk dirty 😘


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## Jarrett (Nov 30, 2021)

carlinb17 said:


> Why did you sub out three of the four 2N5088, the 2N3904 is a medium gain transistor while the 2N5088 is a higher gain one. Not sure if it matters in this build but just curious why. Pictures would definitely be needed to move forward though. Where did you source your BBD's?


I subbed the three because I had one 2n5088 and forgot to order more when I was sourcing parts, then I didnt want to pay $7 shipping for $1 in parts.

The IC's came from amazon -sketchy I know- but I have used some from the same order in other chorus pedals with no issues. These two could still be duds I suppose, but I'm not sure how to go about testing them.

I'm mostly interested to know if it is common that either bad transistors or bbd's could cause a complete loss in sound like that?


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## carlinb17 (Nov 30, 2021)

Jarrett said:


> I subbed the three because I had one 2n5088 and forgot to order more when I was sourcing parts, then I didnt want to pay $7 shipping for $1 in parts.
> 
> The IC's came from amazon -sketchy I know- but I have used some from the same order in other chorus pedals with no issues. These two could still be duds I suppose, but I'm not sure how to go about testing them.
> 
> I'm mostly interested to know if it is common that either bad transistors or bbd's could cause a complete loss in sound like that?



Thanks for the clarification. @fig is spot on with lets look at power first. We cannot do anything for trouble shooting until you get power. do you have a dmm? Also please post pics when you can. The IC's could be an issue but power comes first.


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## Jarrett (Nov 30, 2021)

carlinb17 said:


> Thanks for the clarification. @fig is spot on with lets look at power first. We cannot do anything for trouble shooting until you get power. do you have a dmm? Also please post pics when you can. The IC's could be an issue but power comes first.


I verified the polarity of the power supply is correct. Also I was wrong about the leds. I had the dang things in backwards. I touched another led to the pads to confirm and they are working. Ill switch them around later, but presumably that wouldnt kill the sound.


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## carlinb17 (Nov 30, 2021)

ok so we're headed in the correct direction. lets get some pictures of both sides of the board and the wiring.


edit- I see there are some previously posted.

The BBD's look very suspect.... can you swap them out (it looks like there are no sockets) with your Caesar to see if they work in that pedal? Can you get the get a better picture of the BBD's?


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## fig (Nov 30, 2021)

Check that, and maybe the rest of the values.

Edit: Sorry for the quick response. I did check that quadrant, but was as far as I got. I don't know if that alone would cause the issue or not.


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## JinX (Nov 30, 2021)

huh. done this pedal 3 times and all attempts are fail.
i have question. i used mn3101/3007
for 3101 power supply from datasheet 8-16V - is ok
for 3007 power supply 15V !!! min 14V max 16V

how it should works with standart guitar pedals power supply 9V?
or for these IC i should make special supply for 15V?


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## fig (Nov 30, 2021)

JinX said:


> huh. done this pedal 3 times and all attempts are fail.
> i have question. i used mn3101/3007
> for 3101 power supply from datasheet 8-16V - is ok
> for 3007 power supply 15V !!! min 14V max 16V
> ...


There are a set of jumpers that determine BBD polarity and _maybe_ also adjust Vref ?


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## Stickman393 (Nov 30, 2021)

@JinX a 15v power supply will give you a bit more headroom with a 3007, but only if you use a 15v zener for D101.  A 9v1 will shunt that extra voltage to ground.  That said, the mn3007 is perfectly capable of operating at -9vdc, it'll just clip a little earlier at that operating voltage.

OP...The BBD is certainly suspicious, BUT if you're not currently getting any sound out of the pedal when active I'd say double check around R3, C1, Q1, IC2 (specifically pins 4 5, 6, 7 and 8) as well as R40 and C20.

Also...good idea to make sure you're not mixing up the input and the output.  It sounds silly, but trust me...that one still gets me from time to time when unboxed.


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## Jarrett (Dec 1, 2021)

Okay update... its working!



Stickman393 said:


> Also...good idea to make sure you're not mixing up the input and the output. It sounds silly, but trust me...that one still gets me from time to time when unboxed


This would seem so obvious that it doesn't even need to be said - which is why it didnt even occur to me as a problem until you said this. Because I had the circuit board flipped over I was thinking "in to the right and out to the left" but this shouldve been reversed. 

This didn't immediately solve my problem, but then I quickly realized my trimpot was out of range and not allowing the signal to pass through, so I adjusted it and now everything seems to be working properly.

A Cracker Barrel IQ test once told me I was an ignoramus... I guess Ockham's razor would've been helpful here.


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## Stickman393 (Dec 1, 2021)

Jarrett said:


> Okay update... its working!
> 
> 
> This would seem so obvious that it doesn't even need to be said - which is why it didnt even occur to me as a problem until you said this. Because I had the circuit board flipped over I was thinking "in to the right and out to the left" but this shouldve been reversed.
> ...


No worries there brotha, it happens to the best of us.  I can't tell ya how many times I've plugged in, gone back to the workbench, cussed a bunch, gone back, thrown the pedal against the wall, went back to the bench, cursed, started a world war, gone back to my amp and realized I had it backwards...


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## fig (Dec 1, 2021)

Stickman393 said:


> Also...good idea to make sure you're not mixing up the input and the output. It sounds silly, but trust me...that one still gets me from time to time when unboxed.



Pedal-Fu! You should have opened with;

_I'd like to solve Pat._


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## JinX (Dec 29, 2021)

all attempts i created my personal PCBs.

i saw with osciloscope Low freq genetator works fine. 3007 - i think this IC dosen't work in my case.



another attempt #4. i designed new PCB and ordered 3207/3007. they should work with 9v power supply. if they started work, maybe i try return to 3101/3007

my new PCB 






fig said:


> There are a set of jumpers that determine BBD polarity and _maybe_ also adjust Vref ?


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## Stickman393 (Dec 29, 2021)

^3207/3007?  In case that isn't a typo, you should know that compatible pairings are the 3101(clock)/3007(BBD), and the 3102/3207.

Also, with your own board be mindful that though the pinouts are identical for the MN3007 and the MN3207, the 3007 will require a negative voltage across it's GND to Vdd/Vgg terminals, whereas the 3207 requires a positive voltage across those same terminals.

Also worth noting that applying a positive voltage relative to ground to the 3007, or a negative voltage relative to ground to the 3207, will likely result in a fried BBD.


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## Jarrett (Nov 30, 2021)

I just finished putting together this chorus pedal. I've done the Caesar already as well as a Small Clone clone, so I generally know what I'm doing with chorus pedals, but this time I have no sound when I engage the switch.

I have bypass signal, but evidently I have an open circuit somewhere. I also have no led's (edit: leds are working).

I was wondering... I subbed 3 of the 5088 transistors for 2n3904's because I read somewhere about this being okay in certian fuzz circuits. Could this be my problem? The rest of the build looks pretty clean compared to my usual work.

Edit... okay here are a couple pics. I had to chop them up to get them to upload... sorry about that. Also, thanks guys for the super quick responses!


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## JinX (Jan 7, 2022)

Stickman393 said:


> ^3207/3007?  In case that isn't a typo, you should know that compatible pairings are the 3101(clock)/3007(BBD), and the 3102/3207.
> 
> Also, with your own board be mindful that though the pinouts are identical for the MN3007 and the MN3207, the 3007 will require a negative voltage across it's GND to Vdd/Vgg terminals, whereas the 3207 requires a positive voltage across those same terminals.
> 
> Also worth noting that applying a positive voltage relative to ground to the 3007, or a negative voltage relative to ground to the 3207, will likely result in a fried BBD.


thanks for your reply 👍

PCB is done


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