# Caesar Chorus issue (pics linked within)



## Oh_Discordia! (Mar 8, 2022)

Hi all.

Finished up a caesar chorus build, I'm getting sound when bypassed, nothing when engaged.   Led's both work, LFO pot adjusts flashing LED (seemingly) as it should.  I've reflowed anything that looked suspect and most of the rest.   Cleaned 2x with 99% Isopropyl, still nothing.  

Gave it power and took IC readings:

IC1
1- 0.73-8.02 w LFO
2- 4.2-4.8
3- 2.6-6.3
4- 0
5- 4.1-4.5
6- 2.5
7- 2.4-6.5
8- 8.78

IC2
1- 5.08
2- 5.23
3- 4.96
4- 0
5- 5.03
6- 5.08
7- 5.08
8- 9.38

IC3
1- 0
2- 4.3
3- 4.96
4- 8.22
5- 8.79
6- 4.3
7- 5.87
8- 5.87

IC4
1- 8.78
2- 4.34
3- 0
4- 4.32
5- 0.18
6- 8.57
7- 2.8-3.15
8- 8.2

I saw someone else's thread w values posted and mine are off for some IC's.   Still very much a newbie, so I'm at my technical knowledge limit at this point,  but trying to learn as much about the how's and why's of my mistakes as well as better skills (my reflowing technique is largely reheating and adding a dab more solder -- may need improvement?)

Any help/advice/next steps is very much appreciated.    Thanks!
Pics of board


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## bhcarpenter (Mar 8, 2022)

Honestly it may be as simple as turning the trim pot until you get sound. Mine had kind of a narrow range where things worked.


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## Oh_Discordia! (Mar 9, 2022)

bhcarpenter said:


> Honestly it may be as simple as turning the trim pot until you get sound. Mine had kind of a narrow range where things worked.


Did yours have no sound at all until you dialed the trimpot in?


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## szukalski (Mar 9, 2022)

Yes. That was the same for me. Narrow band where things worked.


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## bhcarpenter (Mar 9, 2022)

Lowtide said:


> Did yours have no sound at all until you dialed the trimpot in?


Yep. No sound if the trimpot isn’t dialed in.


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## Oh_Discordia! (Mar 9, 2022)

Hmmm.   Ok that’s something to go on.   I’ve just now messed w the trim but still nothing.   Think I maybe need to learn to read a schematic/make an audio probe and see how far I get signal.   

Most complex build for me yet, so psyched to hear it.  Of course gives me the most grief. Lol


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## carlinb17 (Mar 9, 2022)

can you throw up some pictures? where did you get your bbd chipset from?


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## Oh_Discordia! (Mar 9, 2022)

Sure. I linked some pics in my first post as they were too big but I’ll get some smaller ones now.  Chipset was from cabintech if I recall.   I’ll take good pics of them as well


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## carlinb17 (Mar 9, 2022)

if their from @Cabintech that's  not the issue


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## Oh_Discordia! (Mar 9, 2022)

now with pics!  and yes, found the order - bought from cabin tech.


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## Oh_Discordia! (Mar 10, 2022)

Ugh this one might have beaten me.   I built an audio probe (yay) and can trace sound until C2.   Neither R9, nor C4 have any sound and I've redone the solder at C2, C4 and R9.     still nothing.  no leg of any IC has sound.   a few have an annoying clicking in time with the LFO

Is it possible that I fried or physically destroyed the trace between C2 and R9?  part of me wants to just jumper it to see what happens.  For now I'm going to put this one on the shelf.


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## Oh_Discordia! (Apr 19, 2022)

Taking another stab at this:

Bypass ok
When engaged I can get the most faint signal when i dial it into a VERY specific spot on the trimpot (way left), but no effect

I've reflowed everything, done a visual confirmation of all values, swapped all IC's  including the 3207 and 3102 (both times from cabintech so i think they're ok) 

Please ignore values from up top, here are current readings w  trimpot set in the middle

IC1 TL022
4.4 fluctuate
4.3 fluctuate
4.7 fluctuate
0
4.5 fluctuate
3.37
4.3 fluctutate
8.75

IC2 (4558)
4.93
5.02
4.82
0
4.89
4.94
4.93
9.4

IC3 (MN3207)
0
0
4.2
8.6
8.7
0
0
0


IC4 (MN3102)
8.77
0
0
0
*6.1*
8.7
*0.66*
8.6


My rudimentary understanding and attempt to trace via the IC pinouts and schematic leads me to thing that pin 5 and 7 in the clock generator may be an issue (which contribute downstream to the bad values in the 3207)

Can someone help me find where to look now? I'm getting a little confused tracing further.   I got as far as Pin 5 from the 3102 to R26 (33k)   this seems to have a value of 6.1 going in and 0.67 out  is this correct?   this then goes to the base of q4?   My q4 values are (EBC  0, 0.67, 0.04)  I think from here everything is off as this is what feeds into pin 7 of the MN3102(?).  Hoping i'm zeroing in on what the issue is but either way im concerned at how much i'm enjoying this learning/troubleshooting.  i think there may be something wrong with me  .  Eternal thanks for any help.








Can


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## Robert (Apr 19, 2022)

Do you have a clean signal if you turn the Blend control all the way up?

If you have no clean signal you can ignore the BBDs (IC3, IC4) for now, the problem is either in the Input (Q1, IC2.1) or Output (IC2.2) stages.


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## Oh_Discordia! (Apr 19, 2022)

Robert said:


> Do you have a clean signal if you turn the Blend control all the way up?
> 
> If you have no clean signal you can ignore the BBDs (IC3, IC4) for now, the problem is either in the Input (Q1, IC2.1) or Output (IC2.2) stages.




No Clean signal.  

so from ic2.2:

Pin 7 - 4.56
R40 4.56 on both sides
C20 - 4.56 one side 0 on the other
R41 - 0

issue with C20?




For reference, C2 has readings of ~5.0 and 0 ....


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## Oh_Discordia! (Apr 19, 2022)

An audio probe gives me (unmodulated) signal at C20 but not C2?    I feel like this doesnt make sense.


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