Cepheid Chorus Help

A

almostjay

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Hey all. Hoping someone might be able to uncover something stupid I am missing. I completed my Cepheid Chorus build today and am testing it on my Auditorium but it is not chorusing. Passing signal but no effect. The LFO seems to be oscillating as evidenced by this video:


Here are pictures of the build:

IMG_9873.jpeg IMG_9872.jpeg

I only have one set of 3207/3102 ICs. I swapped the TL022 and RC4558 to no avail.

Did I bridge the pads by the clock correctly? Anything else sticking out?

Thanks for any ideas!
 
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Jumpers should be ok, both are jumpered for the 3207 right, pic is dark. Where did you sourced the ICs ?

What's going on at bottom left corner?
Also, it looks like sockets could take more solder.
1000003901.jpg
 
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Nic said:
Jumpers should be ok, both are jumpered for the 3207 right, pic is dark. Where did you sourced the ICs ?

What's going on at bottom left corner?
Also, it looks like sockets could take more solder.
View attachment 101754
Click to expand...
The ICs are from multiple sources. I got the clocks and RC from PedalPCB along with the board. The TL022 came from Stomp Box Parts. I tested every component before installing it so I’m pretty sure they are good.

I’ll add more solder to the sockets. Appreciate the thought.
 
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What looks like a short from C2 to R3 in the bottom left corner is the main stand out from your pics.

It sounds like your circuit is being bypassed even when the switch is enabled. Try tweaking the trim pot.

The leads on the back of your board could be trimmed shorter, and a lot of them look like they need more solder.
 
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falco_femoralis said:
What looks like a short from C2 to R3 in the bottom left corner is the main stand out from your pics.

It sounds like your circuit is being bypassed even when the switch is enabled. Try tweaking the trim pot.

The leads on the back of your board could be trimmed shorter, and a lot of them look like they need more solder.
Click to expand...
Oh wow. Good eye. I need to go check yhat short out. Weird.

I did tweak the trim pot. I get no signal at all through the circuit when it is turned all the way CW or CCW.
 
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swelchy said:
also.. the spot on the trimmer that the chorusing kicks in is very very small on the sweep
Click to expand...
Dude. Thank you. I just got this working and it was definitely because of that. I scrapped a trimmer thinking mine was bad but it was definitely this issue.

What is the point of the trimmer if the modulation only works in that tiny window? I guess that tiny window is variable dependent on other components so I can just put a fixed resistor there?
 
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looking closer I can see several pads that do not have soldering coming through to front... specifically there is a ceramic cap and a diode that almost appear to have no solder on the pads... I suggest a really close inspection and reflow.. Bench mounted magnifying lamp helps me a ton.... It's a must for me with my vision.
 
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almostjay said:
Dude. Thank you. I just got this working and it was definitely because of that. I scrapped a trimmer thinking mine was bad but it was definitely this issue.

What is the point of the trimmer if the modulation only works in that tiny window? I guess that tiny window is variable dependent on other components so I can just put a fixed resistor there?
Click to expand...
sort of.. you could but really the trimmer is there for a fixed resistance point because of tolerances with other parts in the circuit.... technically you could find the sweet spot.. pull the trimmer and measure it's resistance then place a fixed resistor in place....
 
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swelchy said:
sort of.. you could but really the trimmer is there for a fixed resistance point because of tolerances with other parts in the circuit.... technically you could find the sweet spot.. pull the trimmer and measure it's resistance then place a fixed resistor in place....
Click to expand...
Did I miss this in the build docs?
 
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... No it's not something most folks would do with a trimmer... We find the sweet spot and move on. Technically pedalpcb doesnt have build docs... really your getting a "bill of materials".. It's a bit of a learning curve for beginners but really forces you to learn some things fast instead of being spoon fed.. Robert spends his time tracing circuits and getting pcb layouts done so he can get the pcb's out to us.. instead of using all that time writing an essay on how to build a pedal. I recommend just searching our forum here on whatever build your going to do next.. read up on people build reports, troubleshooting threads and mods will give you a lot of insight before you go after a build.. especially if your kinda new...
 
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One thing I've done on builds (where I'm designing a new PCB) that have a tiny sweet spot is to use a multi-turn trimpot
like the 3296W instead of the 3362P-style. Maybe it'd be neat to design a little breakout board that could go in the footprint
of the 3362P to replace it with a multi-turn trim?. They're kind of a hassle since they're 25 turns, but give a lot more
precision in finding the sweet spot. Probably the best of both words would be to have both kinds (coarse and fine adjustment)
but that's a lot of PCB real estate.

I think you'd have a hard time replacing a trimpot with a fixed resistor. Remember that the sweet spot is really narrow.
You're probably dialing in something like 6.12K, which isn't a resistor value that exists, so if you go to the closest available
resistor value, you're out of the sweet spot.
 
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swelchy said:
... No it's not something most folks would do with a trimmer... We find the sweet spot and move on. Technically pedalpcb doesnt have build docs... really your getting a "bill of materials".. It's a bit of a learning curve for beginners but really forces you to learn some things fast instead of being spoon fed.. Robert spends his time tracing circuits and getting pcb layouts done so he can get the pcb's out to us.. instead of using all that time writing an essay on how to build a pedal. I recommend just searching our forum here on whatever build your going to do next.. read up on people build reports, troubleshooting threads and mods will give you a lot of insight before you go after a build.. especially if your kinda new...
Click to expand...
Yeah this is fair. Not trying to be snarky. This is my 8th build I think so I have some confidence at this point but I’m still very much a newbie.
 
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