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: 15 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: 411 Location: Raleigh NC

unterbit · Posted: Thu May 23, 2013 8:53 am Post subject:

Hello electro-music.com,Matthias & staff!
Little problem. I suppose i have built 4046vco with success,( i used SSM2210)but only issue i got is some ripple(not that firm spike at top of waveform) but more like "distortedlfo" interference.Funny that when i disconnected COARSE pot,issue has gone and signal appeared nice and clean..(with still connected FINE pot).Then i tried with another 100k COARSE pot & shot temp. wire but ripple came back. Ideas..

elmegil · Posted: Thu May 23, 2013 5:45 pm Post subject:

Shielded cable?

Like from TV cable, single conductor with a grounded (one end only) shield.

diablojoy · Posted: Thu May 23, 2013 9:17 pm Post subject:

check your power supply rails see if its got the same ripple on it.
might be coming from another module on the same supply
say an LFO or something with a led flashing at that rate,
if so maybe you are too close to the max current draw for your supply
or not enough decoupling on one of your modules

fonik · Posted: Thu May 23, 2013 10:52 pm Post subject:

yes.
and the fine pot is much less sensitive. maybe you just don't recognize the ripple.

BTW i once had a faulty potentiometer in the glide circuitry of my klee2. i replaced it, and the problem was still there. the replacement potentiometer has been faulty, too.

unterbit · Posted: Fri May 24, 2013 7:49 am Post subject:

How i could not mention that i have second VCO with the same deviance! and ripple kept in sync for both actually..So its PSU maybe,strangely but yesterday when i re switched the cab.everything was goodworking but today the ripple cameback.
Sorry Matthias for impeach X-4046 then! Need to go check the PSU.and thanks for all comments!

ortazel · Joined: Aug 30, 2013 Posts: 1 Location: US

I am pretty new to modulars and have done very little electronics DIY. I recently bought a secondhand X4046 VCO and the tuning is way off- 1V is more like a major 6th. I tried adjusting the HF and scale trim trimpots according to the documentation here: http://www.birthofasynth.com/Thomas_Henry/Pages/X-4046.html

but could only get it to about a 7th before the scale trimpot ran out- it sounds like it is close to getting to 1V/octave but not quite. I'm using a Minibrute with the arppegiator set on octaves to tune, which might not be ideal but should get me in the ball park at least- my Hertz Donut sounds great with it. What am I missing to calibrate this thing?

The sine out also sounds pretty far off what a perfect sine sounds like. I don't have an oscilloscope, is it even worth playing with the sine trimpots or should I just leave it alone and enjoy my weird sine?

I feel like I just need a slightly lower resistance trimpot for the scale so I can go that little bit further. The trimpots are all Bonems 3296, but all trimpots EXCEPT the scale trimpot have "W 104 / 110 T" printed on top. The scale trimpot has "W 101/ 302B" stamped on top. Should this be the case/is this the source of my problems?

fonik · Posted: Wed Sep 04, 2013 4:20 am Post subject:

so lets work it from the core forward.

to get a 1V/oct scale response you need to use the correct 4046. i.e. a texas instrument part would not do it. i used ON Semi and NXP with success. motorolla is good, too.

so what 4046 are you using?

Danno Gee Ray · Joined: Sep 25, 2005 Posts: 1351 Location: Telford, PA USA

Matthias,

I would be interested in a PCB from your next run.
Do you by chance have panels available?

Dan

Moondog · Joined: Jul 19, 2013 Posts: 2 Location: Chcichester, UK

Hi Matthias,

I too would like a couple of cores and a couple of wave shaper PCBs. Do let us know when you are doing a new run.

And thanks for all the hard work you are putting into the community, it gives great confidence to beginners like me to give it all a go.

Best,

Moon.

fonik · Posted: Mon Sep 30, 2013 8:42 am Post subject:

lately i got intrigued by the idea fo re-designing the PCB in order to facilitate eurorack builds w/o wiring. the same way i did it for the new thomas henry projects: one circuit PCB providing MTA-100 footprints, and an additional PCB for the front panel components, accommodating the eurorack standard.

quite some projects on the pile, so i don't know when this would happen.

Moondog · Joined: Jul 19, 2013 Posts: 2 Location: Chcichester, UK

I can see the attraction, but it would preclude those of us with fat fingers wanting to build these projects to the larger standards.

Do you have any PCBs left?

fonik · Posted: Sat Oct 05, 2013 1:10 pm Post subject: