AS3340 VCO Square output help needed

Hello,

I Build a VCO based on http://modular.ob1techno.com/wp-content/uploads/2019/04/alfa4-vco.png this board (based on Sams design) and I got Saw and Triangle working fine (need work on tuning 1v/oct though) but I don’t seem to get any signal from the square output (pin4) no voltage at all 0.00, as I understand you feed voltage to pin 5 to get the square going or am I wrong? The voltage on Pin5 is 10,9v maybe it is not enough? Checked all soldering and everything seemed fine, used 1% resistors. Is it possible maybe I fried it somehow before? (had some problems at the beginning with the sound)

Running from ±12v supply

The chips description (http://www.alfarzpp.lv/eng/sc/AS3340.pdf)

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Pin 5 is the CV for the PWM output, and the effective range (measured on the pin) is 0-4 V for a 12 V supply. See this thread:

Does the pulse width pot do anything? (the voltage from that one is mixed with the CV in by the second TL072, see here:

If the pot doesn’t do anything, check the wiring for the pulse width and PWM CV pots.

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The pulse width pot when turned changes for like ±0,2V

Here is my Layout of the Alfa4 VCO with addes Eurrack Pin Header and Pots on the PCB, also the Jumpers are coloured red=+12v, blue=-12v and black=GND

maybe it helps.

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So I tried to do it your way :slight_smile:
Checked all the soldering for bridges 2 times and if I did it correctly all the parts
Now the AS3340 only starts to heat up a lot cant even touch it… suppose I fried AS3340 chip or it could be my wiring?

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Here is a web page containing a block diagram of the AS3340 and some suggestions for controlling it. Perhaps you can take the chip out, mount it on a breadboard, and see if you can get some sort of output from it. I think you will need an oscilloscope for this, but if you don’t have one don’t worry, inexpensive oscilloscopes suitable for basic audio work are available on eBay.

https://www.soundtronics.co.uk/as3340-voltage-controlled-oscillator-vco-16-pin-dip.html

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I gonna try breadboarding it.

and upload some pictures maybe I dont see my mistake .

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i check the backside and maybe one or two solder point to “re make” ?

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Measured where? If you unplug any PWM CV input, put both the PWM and the PULSE WIDTH pot in the center, and measure the internal CV on the stripboard (the pink wire in Sam’s drawing, light blue in Olly’s drawing), what voltage do you see there?

EDIT: Nevermind, missed that you had switched to an entirely different layout. Do you still have the original build? I mean, it kind of worked, so troubleshooting that one seems easier than starting over from scratch one more time…

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it’ seems that a little bit of solder touch the line here

9e6cb0c1b7b70deebe56a9ff4c5504163678df73

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I checked this one not a bridge ;/ I always go through every gap with tweezer and see if anywhere i get stuck then i know its a bridge also check at the same time with my eyes :slight_smile:

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It worked, then changed something and now it doesnt… The chip gets hot in this circuit ( reverted back to the working one) and the new that I built (thorges build seem more simpler for me less wires thats why I tried it).

Im afraid that I fried it… (starting to feel really defeated by this project)
Now trying to breadboard it to see if I am right about it being fried.

also can’t thank you enough for being so helpful ! I understand it’s not easy to explain things to newbies :smiley:

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So I breadboarded it the simplest way, and the chip gets hot to touch also… It means ifried it i guess… :frowning:

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Dont be defeated. Sometimes you get these “why the fuck is this not working” angles and you could be scratching your head for a while.

Then you find out why, and its something silly or something new you didnt know and you are better prepared next time.

This stuff isnt easy, but that doesnt mean its impossible. “Dont be scared to try it”, but also dont be discouraged when you hit a wall. Punch through that wall with your relentless determination yo. We are here to try and help however we can.

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Hey, sad to hear it didn’t work for you. Unfortunately I’m in my garden right now and can’t look at my circuit board. But I’m sure the layout works, I built it too. It’s sure as Caustic says it is, a stupid little mistake that drives you totally crazy. I hardly build a module without having to troubleshoot afterwards, something is always! So keep your head up and don’t give up.

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I was in the valley of despair too recently. Dont give up! Sometimes its good to take a break or start over fresh (if that is monetarily feasible). I figure you can always use an extra oscillator!

And I am currently in the same boat as you. I finally got the saw and triangle working, now trying to get the square sorted out.

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That board design looks to be about my level of skill. It looks like a fun build and debug so I’ve taken the leap of buying ten AS3340 chips from Electric Druid.

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Ive build 3 of my 10 or so i bought. There was some teething, but really its not so bad.

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After I went for the 20% off deal I started researching circuits, and I did notice that you mentioned going for the same deal in an old post here. It’s a great idea and obviously a popular one.

I’m a little concerned about the possibility of assembling an untried layout, because there seem to be a lot of them around and if you miss the “by the way I haven’t actually built and tested this circuit” comment you might end up wasting a lot of effort. The Electric Druid resources and the datasheets will be useful here.

I considered buying the original Curtis version of the chip but the prices are too high to be worth it except perhaps for restoration.

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Sam’s 3340 stripboard layout works, I made a mod to add fm, and it works. In mine I noticed some noise on the square that I tried to address, but you might be better off just using Sam’s layout.

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