e-licktronic Forum

Hi all,

last week I (almost) finished my Yocto. It's from a complete kit I got 2 years ago. Shame on me, for finishing it so late. Most stuff worked right from the stuff. Unfortunatly the complete kit contained a fake CD4011BE, so accent is not working, until I get a new CD4011BE. Without it all instruments seem to work fine.

The only issue left is a continous background tone at the mid tom/conga. Hear for yourselves:



https://soundcloud.com/martin-ley-1/mid-tom
The recording is done with the mic-input of my laptop, so ignore the distortion.

The pitch and volume changes when changing the level and tuning pots and switching tom/conga.

Does anyone have an idea, what's wrong?

Those are actually the conga's, not the toms
Ground the switches ( viewtopic.php?f=16&t=720 ) and the noise will mostly vanish
are you using an internal power supply?

I'm using a wall-wart type external powersupply. I will try grounding the switches. Thanks for the advice.

The continuos tone is present on both mid conga and mid tom. In the sound file you can hear, when I switch from one to the other.

Grounding the switches did not improve the sound noticably. The constant mid tom/conga sound is still there.

The low and high tom/conga were fine, even with the ungrounded switch housings.

When I tap with the scope pin 7 of U17, I see a pretty strong signal, when not triggered. At the same point (pin 7 of U15) in the low tom/conga, there is silence.

As Fabi303 guessed correctly in a chat conversation yesterday, one of the germaniun diodes is bad.

The diode tester of my multimeter shows a value other than overload when testing against flow direction.

Now I have to get some replacement diodes (some, because I also need some to build a distortion circuit).