Electrosmith 3340 vco sanity check

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kdmr
Learning to Wiggle
Posts: 44
Joined: Thu Jun 30, 2016 7:24 am

Electrosmith 3340 vco sanity check

Post by kdmr » Sat Sep 12, 2020 11:32 am

I built two of these guys under a panel and they are both exhibiting the following weirdness. They both used to check out on the scope. I was patching a few nights ago and noticed that my linear fm behavior was off, like kind of stepped voltages with a triangle in with maybe 3 steps per slope. Threw them both under the scope (tried multiple power supplies and all waveforms) and I'm getting the proper shapes, but the negative incursions max out at like 2.x volts. Moving the tuning pots to the rail makes the entire waveform cross into the positive plane, maybe 0.5-7 volts or so. Voltages seem to check out, I just need someone with more 3340 experience to tell me if the chip is shredded. V/OCT control still works great, as do pwm and sync inputs. Seems odd that the same issue came up on both of them at the same time.

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