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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sethaberry said:
I adjusted it while out of the box until it was working and then tried again when in the box. I went nice and slow through the range of the pot, but still nothing but clean.
Click to expand...
Well id be sus of your pot backing. As the only real difference should be the that its not getting pressure on that pot being tightened down to the board.
 
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is the rate led working in the box?

Check your voltages on q5, and check is both sides of c16 have continuity with ground.

All three of these things would be effected if that pot is grounding out. And all three are in the chorus portion of the circuit.
 
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Awesome. It started producing chorus in the box, but then started to gradually fade out to just dry after a few minutes. All LEDs are flashing as needed.

Laundry is calling my name, so I'll check those spots for continuity soon!
 
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Here's what I've got on Q5:

Emitter - .912
Base - 1.44
Collector - 8.94

One side of C16 is closed and beeps (the left leg, as you're looking at the populated board), and the other is open.

Just to take it out of the equation, I changed the cardboard and electrical tape for some thicker polystyrene -- zero shot of nubs getting through and making contact.
 
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sethaberry said:
Awesome. It started producing chorus in the box, but then started to gradually fade out to just dry after a few minutes. All LEDs are flashing as needed.

Laundry is calling my name, so I'll check those spots for continuity soon!
Click to expand...
Strange, if you unplug it and plug it back in does the choris effect come back and then do the same fade out? That would make me suspect a cap.
 
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sethaberry said:
I just tried that a few times, but it didn't produce any change. What I wouldn't give for a "turn it off and then on again" situation! :ROFLMAO:
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How long did you leave it unplugged for? Caps gotta discharge lol. Well i would probably revert to the audio probe again and see if tou can see where you lose that wet signal. I like to check at actives. So q3 emitter, ic3 pin 3, pin 7, q5 emitter
 
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I'd be lying if I said I waited more than a few seconds on the first try! I left it for a whole day, though, and tried again, with no change.

I'm not getting anything from Q3. No change with a different transistor.

I'm getting dry signal on Q5's base, but nothing on the emitter. I swapped a different transistor, but it had the same behavior.

I'm also getting a dry signal from pin 7 on IC3, but nothing on pin 3.
 
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Any one agree he should unbox it.. run power to the board , bend pots up clear of the pcb and plug in the in and out jacks correctly to give it a gut check to make sure pots not touching something their not supposed to be?
 
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