Another CEM3340 problem post

Hi guys, sorry to make another one of these, but I’m going mad trying to figure out what’s wrong with my circuit.

I’m a newbie so I thought I’d try the simplified version of the performance oscillator (with just saw and tri outs). I’ve seen the annotated layout that fredrik posted, and all my voltages line up. I’ve checked the continuity between every strip to make sure there were no shorts that weren’t supposed to be there. I’ve checked continuity across the drill bit separation and we’re all good there. I’ve multimetered all my resistors and they’re all good. I’ve double checked my wire jumps. I can’t figure it out!

The only thing I can think of at this point is that I hooked up power before I realized I hadn’t made the wire jump from pin 4 of the op-amp to pin 10 of the AS3340 and that somehow fried the 3340. However that part of the circuit seems to be more about conditioning the output than supplying power.

Sorry it’s all so cramped. I started drilling out the stripboard before I realized I had to place the components in on the other side, haha. Also when I was buying components I assumed the 1 watt resistors were somehow better than the 1/4 watt ones and didn’t realize how big they’d be!

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I just checked the cv voltages and I’m able to get up to 12v going through the top lead of the resistor which is closest to the AS3340, and it does change when I twist the pot. I also checked continuity of the jack sockets onto the stripboard and we’re all good there.

I don’t have my CV jack wired in yet, but from the looks of things I don’t think it should make a difference.

You haven’t actually said what the symptoms are.


Oops, you’re right. I’m not getting any sound out of either jack socket. There’s only some faint white noise.

Are you looking at it with a scope? Or just listening for it?

It’s unlikely you fried the 3340 unless you misconnected power to it. If it’s not fried I think it’s pretty hard to get a 3340 not to oscillate if you’ve given it power. Maybe in a completely wrong frequency range in which case you might have trouble hearing it.

Or the problem could be downstream of the 3340. A problem with the TL072 could block both waveform outputs. If you don’t have a scope you can try listening to the output pins on the 3340 using an audio probe.

From what I see the resistors look to be the right values (the 1.5M is partly hidden but I guess it’s right). The film cap is correct, the ceramic I can’t tell, it should say 102 on it. (Film would be better for that cap but ceramic should function well enough.)

You have strip cuts on between the two sides of each chip on every strip?


Thank you for your thorough response. I have one of those cheap red $40 oscilloscope kits but I’m not quite done making it yet. I’ll finish it up (hopefully it works!) and try hooking up the signal through that and let you know how it goes.

I’ll also try replacing the TL072 and see if that does anything.

Yes, that 1nF capacitor does say 102. I also replaced it early on in my troubleshooting but it didn’t help.

And yes, I’ve stripped the column on the back surface between the chips from the top of the trim pot to the bottom of the TL072, and I’ve checked continuity on every row and I know there isn’t any current getting through.

If everything goes well with the oscilloscope I’ll try that audio probe and report back. Thanks again!