e-licktronic Forum

Dear Kluber,

It seems that only noise is working on low tom. You have to check the oscillator.
Measure with a scope the signal you get when Lowtom is trigged at IC15 Pin7, Pin1.
Post result here.

Best regards,
e-licktronic

Hey Vincent,
I tried to measure with the scope pin 1 and 7 and the signal is too weak to get any result. What would be the measurements you if it's everything normal?

I bought a new IC 4558C and nothing changes.

I resoldered all the pins on the LowTom section.

No luck so far.

BUT the low tom came back for a short time twice when I plugged the PSU... Not sure what's going on here

OK, I finished the electrical part of my build this afternoon and fired the Yocto up for the first time.

I was initially listening to each of the sounds to see how much adjustment I had to do and to my relief most are spot on. Handclap needs a few subtle tweaks but all well and good… until the High Tom dropped out just like Kluber’s.

The High Tom was sounding great, then it became just a huff with no body to the sound.

The Yocto was physically static so no wires can have moved. I was just turning individual level pots up and soloing each instrument. The High Conga sounds a bit quiet now too.

LFO2VCO

Did you manage to have a listen to my soundcloud link?
Do you have exactly the same issue?
Did you try to measure with your oscilloscope what Vincent did suggested?
I didn't get the measures however I've changed the IC but no luck...
If I could understand the theory on the Tom section it would be easier though.
Maybe we should test the diode...

Wow how strange I have just replug the PSU today and the LowTom works just like it should...
It seems there is a bad solder somewhere on the PCB

Hey Kluber,

It was quite late when I got the rascal up and running, so I decided to leave tests until I have a bit of spare time.

I’ll check Vincent’s suggestions for sure… I’ll also try to decipher which resistors and capacitors make up the + – power supplies for the High Tom. I doubt that the IC is to blame as the noise component is still audible. I was also wondering about the transistors or as you suggest diodes.

Odd that we have similar (on the face of it) issues.

Well, as I said the Low Tom works fine so far without touching anything since 2 days... And I had resoldered back then all the pins of this section...
So I'm guessing there should be some bad soldering here and there, don't you think?
I was going to buy some germanium diodes, and a couple of transistors, but I don't need too...

lfo2vco wrote:I’ll also try to decipher which resistors and capacitors make up the + – power supplies for the High Tom.

I don't get what you mean...?

I’ll keep my fingers crossed that my Tom wanders back too Glad your Yocto is fully functional now.

What do I mean… each instrument has it’s own branch from the positive and minus power supply. These spur off from the pads on the main board +15, +5, –15 and ground and run along the top edge of the board as a row of 21 capacitors and resistors (I think). I have had flu for the last week so I could just be delusional…

Alright get it!
You might check minus/plus pads then.
If you weren't touching the PCB when the High Tom went faulty, then I'm guessing there is something with a faulty solder.
I doubt a component died/burnt just like that!

High Toms are back, I went over the circuit with a hot iron. Must have bee a faulty joint.

Hurray!

Happy for you!