Caesar Chorus no effect

Quirkey

Active member
Hey Y'all

First: a shoutout to everyone here who has posted before - searching this forum has helped solve numerous issues in the past couple of months as I've (re) picked up a pedal building addiction after a 20-year hiatus.

I've read up on other Caesar Chorus problems and tried a bunch of things but I can't seem to figure this one out.

Clean signal is fine, with the pedal on, and the blend knob all the way to clean - also perfect clean sound. Rate led blinks properly with the rate knob. Switch works to turn on/off the red leds.

However, with the blend all the way to vibrato - nothing. No signal. With my first set of 3207 chips I tried adjusting the trim and at one point got what sounded like the distorted vibrato but then it fizzed out and no signal came back. I switched the trimmer to a multi-turn thinking maybe I could get a "perfect" trimmer placement more easily but that seems to yield the same result: I'll get a distorted vibrato signal for a second then it will get louder and more distorted and then "fizzle" out.

I've tried a bunch of different 3207 chips (some from eBay and even a much more expensive one from GuitarPCB) but it doesn't seem to change it.

Any ideas? I checked my capacitor values (as that's been a problem in the past) and it seems OK.

Thanks in advance.

--AQ


 
Sounds like you LFO is working (LED blinking). Set Depth to minimum and Rate knob to maximum and check pin 2 or 4 of your clock with the frequency setting on you DMM. It should be around 60-80kHz. The clock needs to be working for the delay line to work.
 
I have the Proster VC97, looks like the VC99 on Amazon is the new model ~$40. I think it's a good investment if you plan on more BBD builds.

You could also post some voltages of all four chips, in the meantime. There is a trouble shooting thread where I posted the voltages of my working unit. Off voltages can help you identify the problem zone. Since you have clean signal and the LFO seems to be working, you likely have a clock or a delay line problem.
 
OK! Long delayed update. Thanks to @Bio77's advice I got a multimeter with a Hz function and tested the clock chip and whoa! it was way off - reading 300-400khz. I had a feeling these MN3 chips I got off ebay were faulty but i had (wrongly) assumed it was the 3207 not the 3102. I noticed Cabintech had some NOS back in stock so I ordered those and once they arrived, swapped them out and VIOLA! after tweaking the trimmer it sounds great/works perfectly. Now on to some other chorus-based builds. Pic of finished build attached (decorated by my 6YO daughter)
 

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Sounds like you LFO is working (LED blinking). Set Depth to minimum and Rate knob to maximum and check pin 2 or 4 of your clock with the frequency setting on you DMM. It should be around 60-80kHz. The clock needs to be working for the delay line to work.
That’s some great info. I’m having pretty much the same issue. My clock hz on 2 and 4 are both 30. I’m assuming that’s my issue as well.
 
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