Caesar Chorus: No rate LED or effect

S

sethaberry

New member
With over 50 pedals (ranging from stripboards to kits) and 2 amp builds under my belt, I've finally run into a problem that's got me a bit stumped. I was pumped to build the Caesar, but I'm struggling to get any joy.

Behavior

Everything behaves as it should when bypassed. When powered, the indicator LED is on, but the rate indicator remains unblinking. When the blend knob is set to fully dry, the clean signal comes through as it should. As the blend knob moves towards wet, there is no signal.

What I've Tried

All of the following have been tried since taking the attached pictures.

Slowly tweaking the trim pot.
Reflowed all joints (has worked for 95% of the problems that I've encountered) and scrubbed PCB with alcohol.
A check of component values. I went through each component and confirmed values against the sheet, but if I missed one on install, there's a nonzero chance that I bungled the inspection too.
Some audio probing. I can get the clean signal from input through output. At no point have I heard anything close to a modulated signal. I can get sound coming off a few IC pins.
Switched the 9.1V diode. I wondered if I hadn't put in the right diode, but no behavior change with a confirmed Zener.
Tried new ICs in all positions.
Replaced all transistors.

There is a piece of cardboard and electrical tape underneath the wet/dry pot. 1000004192.jpg 1000004193.jpg

Suspicions

I've used them before, but the 220U capacitor is just 10V.
I tend to use whatever capacitor types that I have on hand, so I'll use an MLCC instead of a box film if I have the value already. It isn't something that's ever given me an issue, but stranger things, I suppose.
There's a trace broken somewhere.
I've got a misvalued component somewhere and I just haven't caught it.

I've followed a few other posts similar to this, but haven't had any luck with the suggested fixes. Any help would be greatly appreciated!
 
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Electrical tape on the back of a pot is the first red flag..... do yourself a favor and get something more substantial behind the pot..... piece of thin plastic at least.. likely the cause of your issues but sounds like your clock section is not working as well.... Where did you source your BBD chips is next question. Thirdly get yourself some 99.9% isopropyl alcohol and clean up all the schmooo on your pcb as well.. Let's start there and report back?
 
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Thanks, swelchy. I have a piece of cardboard between the pot and the electrical tape (you can see the cardboard peeking out on the side). The board has been scrubbed since the pictures were taken, with no change in operation.

I got one set of chips from PedalPCB and another from Aion FX. Both tried, but producing nothing.
 
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make sure to have blend knob about mid way.. depth all the way up
audio probe pin 3 of IC3..
audio probe pin 7 & 8..
audio probe R35 and let us know what you hear...
 
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The rate LED not working is the biggest clue. You’re lfo is not working. The TL022 is your LFO. I would focus on that.

IMG_1989.png
I’d start by verifying vref_b. And the voltages on the tl022. 0 at 4, around 9 on 8, around 4.5 on pins 2/5, 3/6/1/7 i believe should fluctuate. But i believe your issue is going to be in that area.
 
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Definitely on to something there, Locrian! Thanks for narrowing things down!

0 on pin 4
.22 on pin 8
109.8 mv on pins 2 and 5
Consistent at 109 mv on pins 1, 3, 6, and 7

I'm getting the same 109 mv vref at R4 and leg 1 of the depth pot.
 
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sethaberry said:
Definitely on to something there, Locrian! Thanks for narrowing things down!

0 on pin 4
.22 on pin 8
109.8 mv on pins 2 and 5
Consistent at 109 mv on pins 1, 3, 6, and 7

I'm getting the same 109 mv vref at R4 and leg 1 of the depth pot.
Click to expand...
You got something funky in the power section it looks to me. I’d look at orientation of the 9v1, whats your voltage on the positive side of the 220u? Check your voltage divider resistor values etc
 
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Pin 8 is coming in at 9.04.

The + side of C104 is .22, which feels very wrong.

Both sides of R102 are at 9.04. It looks like a 33R resistor in there.

Diodes and electrolytics are all oriented correctly.

Thanks for all the help; it's very much appreciated.
 
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sethaberry said:
Pin 8 is coming in at 9.04.

The + side of C104 is .22, which feels very wrong.

Both sides of R102 are at 9.04. It looks like a 33R resistor in there.

Diodes and electrolytics are all oriented correctly.

Thanks for all the help; it's very much appreciated.
Click to expand...
Huh im a little confused how both sides of 102 are 9.04 and the plus side of of 104 is .22. Is your solder joint good there? What are you getting at the collectors of the 5088’s. And yes its very wrong
 
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sethaberry said:
Pin 8 is coming in at 9.04.

The + side of C104 is .22, which feels very wrong.

Both sides of R102 are at 9.04. It looks like a 33R resistor in there.

Diodes and electrolytics are all oriented correctly.

Thanks for all the help; it's very much appreciated.
Click to expand...
i think if it was me at this point I would remove c104 and see what your voltage reads. Maybe being a 10v cap it went boom, though boss notoriously used 10v caps in many pedals.
 
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I'll definitely give that a try. It should have the same voltage on the + side as what is coming out of R102, right? I've used those 10 volt 220U caps before, but maybe I just got lucky.

I did pull the blend pot up and reflow all of the solder joints under there, but no change.

I'm getting 9.04 on Q1, 3, and 5. Q4 is .28 and Q2 is .22.
 
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sethaberry said:
I'll definitely give that a try. It should have the same voltage on the + side as what is coming out of R102, right? I've used those 10 volt 220U caps before, but maybe I just got lucky.

I did pull the blend pot up and reflow all of the solder joints under there, but no change.

I'm getting 9.04 on Q1, 3, and 5. Q4 is .28 and Q2 is .22.
Click to expand...
yea it should be the same. Do you have continuity between r102 and the collector or q2 or q4, or the positive side of c104. Or the cathode of the 9v1 diode. Almost seems like theres a bad trace. R102 should have continuity with all those points and should have the same voltage. Short of a bad trace I’m not sure how it wouldnt. If you don’t have continuity with the c104 side of r102 and the positive side of c104 try running a wire on the solded side from the r102 pad and the positive side of c104.
 
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You are the absolute dude! Before checking continuity, I just hit those pads with a touch-only jumper and the rate LED fired right up. Time to solder that into place and test it all out.

Now I'm curious as to how a bad trace happens!
 
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sethaberry said:
You are the absolute dude! Before checking continuity, I just hit those pads with a touch-only jumper and the rate LED fired right up. Time to solder that into place and test it all out.

Now I'm curious as to how a bad trace happens!
Click to expand...
Most likely somehow id guess the pad of r102 got damaged. During soldering. Did you desolder that pad for any reason? Less likely manufacturing defect in just your board.

If it wasnt a verified pcb design built by a ton of people, improperly done layout. Thats obviously not the case here.
 
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Nope, no desoldering and the iron isn't crazy hot. 100% not a manufacturing or design defect, so I must have done something to it! I suppose it had to happen eventually.

I tested it out of the box and all worked great. Once it got in the box, though, I'm not getting any chorus. The rate LED is still going and the LEDs are going.
 
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sethaberry said:
Nope, no desoldering and the iron isn't crazy hot. 100% not a manufacturing or design defect, so I must have done something to it! I suppose it had to happen eventually.

I tested it out of the box and all worked great. Once it got in the box, though, I'm not getting any chorus. The rate LED is still going and the LEDs are going.
Click to expand...
Did you adjust the trim pot
 
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sethaberry said:
Nope, no desoldering and the iron isn't crazy hot. 100% not a manufacturing or design defect, so I must have done something to it! I suppose it had to happen eventually.

I tested it out of the box and all worked great. Once it got in the box, though, I'm not getting any chorus. The rate LED is still going and the LEDs are going.
Click to expand...
Sorry you had chorus out of the box and none in?
 
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