Caesar Chorus No Output

J

Jmarqusee

New member
Hey all!

First time poster here, second PedalPCB board build. Havin some trouble getting my Caesar to work. Got an audio probe on the way from Rattlesnake to go on a part by part hunt, but i figured i'd drop this line first to see if anyone wanted to lend a helping hand.

Similar to other posts i've seen on the subject, i'm getting output issues and there are some weird IC values i'm registering at the same time. Here is a rough outline of the things going on:

1) All LEDs are functional, including the two indicators when toggle engaged. All pulsing seems appropriately timed.
2) True bypass works great, and without any supplemental noise that i would assume is a grounding issue.
3) Only get a slight whisper of a signal when pedal is engaged, input maxed out on a high gain pedal, and blend is CCW. This only present in a smaaaaall subset of the trim pot setting. Following recommendations i've seen, i found the pop on the trim pot and adjusted ever so slightly to get this sound. Otherwise pretty much silent.
4) Had my friend look over some multimeter values and he said the 4558D is acting weird. the vrefs aren't correct and 1/2 pins are giving values. here are those numbers

1: 8.36 // 2: 8.33 // 3: 0 // 4: 0 // 5: 0 // 6: 2.47 // 7: 8.46 // 8: 9.15

5) Friend's recommendation was to reflow resistors and caps that feed into 4558D. I figured i'd ask this forum for more guidance. I'll be sure to post some images of my board shortly as well.

Thanks for all your help!
 
Sort by date Sort by votes
Start by reflowing the circled areas. These are just a handful of rough joints at a glance. The one on the footswitch is the circuit input. That could be the real issue. It wouldn't affect bypass only the circuit when engaged.

IMG_1712.jpeg
 

Attachments

  • IMG_1710.jpeg
    IMG_1710.jpeg
    621.2 KB · Views: 14
Upvote 0 Downvote
if the power to your circuit is wonky you'll end up with no sound with the effect engaged. Touch up the soldering on your hook up wires so you can make sure the board is getting power, then check the IC's again
 
Upvote 0 Downvote
Reflowed everything

New 4558D IC values

1: 1.5 // 2:1.5 // 3:.77 // 4:0 // 5:.77 // 6:1.03 // 7:2.17 // 8:8.8

Changes in sound: I get more of the input than before, unchanged by pedal, and the lag pot has a coordinating high pitch ringing to its intensity now

Also: pin 3 on IC chip makes a sound like a bare jack when touched with the micrometer, as in a guitar cable not otherwise plugged into anything but tapped with just the tip of your thumb (as best I can describe the noise)
 
Last edited:
Upvote 0 Downvote
Spent a bunch of time on the pedal today, essentially trying a full resolder/flow on every point after doing a trace between components i thought might be malfunctioning. Took a while. Nothing really figured out yet; behavior stays the same.

I did notice that when the pad of my finger was placed across a small amount of the lower board i was registering full effected signal. Obviously still had a lot of extra white noise present, but at least i know the thing can produce with the components presently on the board.

Should be mentioned that I’m seeing consistent numbers across the transistors and ICs. Been verifying readings with a friend that builds pedals professionally.

Thanks again for any insight.
 

Attachments

  • IMG_8829.jpeg
    IMG_8829.jpeg
    168.4 KB · Views: 7
Last edited:
Upvote 0 Downvote
Looks like your trim pot is turned all the way down, Try setting it at noon and make small adjustments up and down. I like to "see" what Im adjusting so if you want you can set VREF with a meter. On mine pins 1-3 and 5-7 are set right around 6v, pin 4 is ground so 0, and pin 8 is source voltage.
 
Upvote 0 Downvote
mkultra69 said:
Looks like your trim pot is turned all the way down, Try setting it at noon and make small adjustments up and down. I like to "see" what Im adjusting so if you want you can set VREF with a meter. On mine pins 1-3 and 5-7 are set right around 6v, pin 4 is ground so 0, and pin 8 is source voltage.
Click to expand...
Yeah, that picture was before i went back onto the board and starting setting values in the ideal place. Currently running the trim at a position that doesn't give any output when engaged, but feeds the appropriate vref values to IC2 (4.5-4.6). The former position the trim was in gave a very faint amount of output, which is why i felt it necessary to include it in the image.

My intention is to go through the whole schem and chart out values per component. Was going to do that this morning but the power went down. Womp. Gonna post that image as soon as i get it done.

Thanks :)))
 
Upvote 0 Downvote
Jmarqusee said:
I did notice that when the pad of my finger was placed across a small amount of the lower board i was registering full effected signal. Obviously still had a lot of extra white noise present, but at least i know the thing can produce with the components presently on the board.
Click to expand...
This is a big clue. Make an audio probe and use it to figure out at what point the signal drops out. You likely have a short or an empty solder pad somewhere.
 
Upvote 0 Downvote
falco_femoralis said:
This is a big clue. Make an audio probe and use it to figure out at what point the signal drops out. You likely have a short or an empty solder pad somewhere.
Click to expand...
Thought so. I ordered an audio probe from rattlesnake that should arrive later this week. Sooner than make a thing that introduces other problems, i figured i'd get something from a group that makes them professionally. We shall see!
 
Upvote 0 Downvote
You must log in or register to reply here.
Back
Top