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LZX Cadet VCO layout DIY
MUFF WIGGLER Forum Index -> Video Synthesis  
Author LZX Cadet VCO layout DIY
FetidEye
Hi

I'm making layouts of some of the LZX Cadet modules, with Eagle.

As learning examples, I've succesfully made the C10 Multiplier and the summing mixer.
(pcb's made and tested)

Now I'm working on the VCO.

Does anyone know what the net name "U7_+IN" means?

There is no U7 IC, so it might be some old identifier.
There are 2 nets with this name, the output of the cd4066 (pin 9 goes to R8, then to the net name)
and at R25, near the VCO_CORE_BUFFERED net.

The "+IN" part sound like it must go into an OPAMP.

It might be enough that these 2 nets are connected, but I want to be super certain!

If I have some room left, I want to make extra outputs, rising and falling SAW waveforms, which are super useful.
And maybe some more stuff, if I can find something useful like an inverted TRI / SQ, or some voltage normalled to the CV input so that the VCO goes lower by default.
vonkhades
FetidEye wrote:
Hi

I'm making layouts of some of the LZX Cadet modules, with Eagle.

As learning examples, I've succesfully made the C10 Multiplier and the summing mixer.
(pcb's made and tested)

Now I'm working on the VCO.

Does anyone know what the net name "U7_+IN" means?

There is no U7 IC, so it might be some old identifier.
There are 2 nets with this name, the output of the cd4066 (pin 9 goes to R8, then to the net name)
and at R25, near the VCO_CORE_BUFFERED net.

The "+IN" part sound like it must go into an OPAMP.

It might be enough that these 2 nets are connected, but I want to be super certain!

If I have some room left, I want to make extra outputs, rising and falling SAW waveforms, which are super useful.
And maybe some more stuff, if I can find something useful like an inverted TRI / SQ, or some voltage normalled to the CV input so that the VCO goes lower by default.


yup its weird...



so I guess is just an old idenifier maybe the U7 got removed and the connection tag/label was not updated... looks like in this picture is for the buffer of the output.

BTW do you think would be possible to hack/modify the official pcbs to got those outputs you mention? I would me amazing to have ramps in addition to the triangle and square that we already have.[/img]
vonkhades
I guess you already know, but just in case.. buffers are widely used on signal outputs of modules so for instance voltage doesnt drop if you stack bananas/minjacks or/and to bump up signal.
FetidEye
So it might have to connect to +in of U1 (or U20?), you think?

Going to test this with a multimeter, I have 4 VCO's in my rack, so I can check this realtime.

If you patch the TRI out to a Fader input and the SQUARE output to the CV input of the Fader, you will achieve the Ramp waveforms.
So I was thinking to strip down the Fader circuit and add it to the VCO layout.
The two Fader pots are not needed, so that saves space.
FetidEye
A global test shows that R8 and R25 are connected, but I can't find more connected points (no IC's or resistors)

w00t The layout is done, hardcore routing on this one!
I've added a SQ output.
No room left for the ramp circuitry + outputs, going to make an external PCB for this.


if anyone has a picture of a bare VCO PCB, that would help !
(with all those resistors covering my pcb's, it is hard to pinpoint locations~)
smrl
Yeah, that net is connected to R8, R25, C18, and pin 2 of 74HC14 (U12). Nothing else.
FetidEye
ok, thanks. screaming goo yo

note: I think you meant pin 3 of 74HC14 (U12.2) ?
(12.2 = 2nd inverter, pin 3 and 4)
smrl
yeah, I did mean pin 3. Sorry about that smile
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