Madbean Rustbucket CD4047 Problems

[dobo2001]

Link to build docs/schematic: https://www.madbeanpedals.com/projects/_folders/FilterMod/pdf/RustBucket2019_rev1.pdf

Still having some issues with my Rustbucket build. I've traced the audio to the input pin on the MN3007, however, the output pins just produce a static.

I'm fairly sure the CD4047 is causing the problems, as the signal arrives normally at Pin 3 of the MN3007, as well as pin 2 of the Bias trimmer, however, it leaves the MN3007 as the static.

Pins 1, 2, and 3 of IC5 (4047) also produce the static, along with pin 11. For some reason, when the CD4047 is installed, all of the pins have continuity to ground, something which stops when it isn't in there. Reflowed all the joints for the IC and around it, no change. Voltages are what they're supposed to be at.

The MN3007 also passes signal while the CD4047 is uninstalled, albeit without any effect. I've tried multiple different CD4047's and they all have the same problem. Any help appreciated!

Pics of the board: https://imgur.com/a/vZvJntk

[Rob Strand]

Check out the CD4047 datasheet,
https://www.alldatasheet.com/datasheet-pdf/pdf/80422/NSC/CD4047.html

Pin 13 is the primary oscillator output.    If you have a frequency meter or oscilloscope check the frequency on pin 13 is,

f = 1/(2.2 RC) = 1/(2.2*220p * 27k) = 77kHz

The frequency on pins 10 and 11 should be half that.

If you don't have a frequency meter you might be able to see about -7.5V on pins 13, 10, 11.


Check your resistor and cap values on the 4047.

[anotherjim]

The 4047 probably has internal anti-static protection diodes between its pins and its + and - supply pins. The diodes are reverse for normal operation so don't act - but you can get a reading with a DMM on continuity if the meter probe polarity forward biases those diodes. So reverse the meter leads if you get a reading when checking for shorts. If it reads both ways, you may have a short. If it only reads one way, you probably don't.

If you have an IC socket, that could be bad. With the chip out & power off, check continuity between socket pins on top to prove the pin connects to the right places on the pcb. Also, check continuity between adjacent socket pins. There can be components between those pins that can give a reading, so look at the schematic to see what's there. For example, there is a cap between pins 1 & 2 so that should read open circuit. There is a resistor between pins 2 & 3 that should read 27k then open between 3 & 4 then short between 4 & 5 and so on.

[dobo2001]

Check out the CD4047 datasheet,
https://www.alldatasheet.com/datasheet-pdf/pdf/80422/NSC/CD4047.html

Pin 13 is the primary oscillator output.    If you have a frequency meter or oscilloscope check the frequency on pin 13 is,

f = 1/(2.2 RC) = 1/(2.2*220p * 27k) = 77kHz

The frequency on pins 10 and 11 should be half that.

If you don't have a frequency meter you might be able to see about -7.5V on pins 13, 10, 11.


Check your resistor and cap values on the 4047.

I think I might have the wrong cap value on the 4047, that MLCC has a 334 code on it instead of the 221 it should be. Gonna order some parts from Mouser and swap it out. Thanks!