PCBs for Thomas Henry's X-4046 VCO

Argitoth · Posted: Sun Sep 09, 2012 11:16 am Post subject:

What is going on? Look at what my multimeter gave me for resistor readings. I made doubly sure I was only touching the legs of the resistor. RED = multimeter shows wrong value. BLUE = BOM value. I re-tested R17 multiple times, even testing it from the bottom of the PCB. All resistor markings are correct, but the value isnt?!?!?! Shocked

What's more interesting? The PCB I have not wired (my other waveshaper) shows the correct values on my multimeter! Shocked

Edit: On my second waveshaper, the multimeter shows 45.7K for the 2.2M value (R55). That's the only resistor that shows the wrong value.

Edit: RE-uploaded image. YELLOW = 2nd waveshaper wrong values.

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elmegil · Posted: Sun Sep 09, 2012 11:39 am Post subject:

When the resistors are soldered in, they will be connected to other components that can and will give you readings different than the nominal value.

For the really basic example, if I have a 100k resistor that is mounted parallel to the CW and CCW legs of a 100k pot (this is not a real world example), if I try to measure it I will read 50k--because it's seeing the two 100k's in parallel.

There's not likely to be anything QUITE that simple in this circuit, but I have never been able to read resistance reliably once the circuit is soldered together. It *is* dependent on the details of the circuit, however....

fonik · Posted: Sun Sep 09, 2012 1:15 pm Post subject:

Argitoth · Posted: Sun Sep 09, 2012 1:21 pm Post subject:

Yeah, I think my next step is to wire my other X-4046 VCO and put this one (the one we were debugging) through an oscilloscope to ensure the DC trimmers are correct. I do want to correct the weak sine signal. I'll have to debug that later. I know Dave Brown does debugging. Is there anyone else I might ask to look at my waveshaper if I can't figure it out?

Edit: As for the PWM init sensitivity, the square is now audible most of the turn, so that's good. Haven't tested PWM cv.

fonik · Posted: Wed Sep 12, 2012 12:14 pm Post subject:

BTW to all who are concerned/interested, i will order a few more PCBs end of month. so if you need some more, just tell me.

Argitoth · Posted: Thu Sep 13, 2012 3:15 pm Post subject:

COMPLETED!!!! This is my second build, works flawlessly. Now I have this one to compare with my other one.

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FINALLY!! FINISHED!!! JEEZ!!!

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and some wiring pr0n.

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Argitoth · Posted: Thu Sep 13, 2012 5:48 pm Post subject:

omg fonik!!! Evil or Very Mad

the AC/DC switch is so weird!

I'm using an SPDT on-on, Mouser #: 629-GS1150511

AC to top pin, DC to mid pin... wrong
DC to top pin, AC to mid pin... wrong again.
Turn the switch 180 degrees... correct!

wtf? Question

HansRL · Joined: Nov 17, 2012 Posts: 11 Location: Norway

Hi.

Not sure if this is the popper way to indicate interest in the next batch, if there is going to be a new run of this PCB set?

Or if someone have an extra set they like to part with they can PM me?

Please excuse me if this is considered rude or improper behavior on this excellent forum.

thank you!

Mongo1 · Joined: Aug 11, 2011 Posts: 392 Location: Raleigh NC