Good work! It is good practice to label unverified layouts as such to help people who are arriving here from the net. Would you mind re-uploading the image with a little “unverified” on it?
I built it out and its not working. Anyone have any troubleshooting advice? As far as I can tell the wiring is correct. Using a multimeter I can see that that the internal oscillator is working. The LED is not lighting up but there is fluctuating volts on the positive leg and on the collector of the transistor.
If I measure the output it is very low.
The led is flashing and I have a nice square wave on the collector and base of the transistor. However the signal that is coming out of the LF398 chip is still low and doesn’t seem to be effecting the 3340 VCO I’m testing it with.
If I look at it with an oscilloscpe it seems all over the place. I am using a square wave from the same vco as a source then coming out of the sample and hold back into the CV on the 3340 VCO. Then I have the triangle output going to a small test amp.
I am using a polypropylene capacitor in place of a polystrene cap.
If you’re sampling an audio frequency square wave at low frequency then you should get either maximum or minimum values out essentially at random. If you’re seeing intermediate values then something’s not right.
An LFO input, say a ramp or triangle wave with frequency well below the clock, might be better for diagnosing.
Do you get something like 3 µs pulses with amplitude ~ 2.5 V at LM398 pin 8?
I don’t see any further errors in the layout and assuming you get good pulses into pin 8 the rest is up to the LM398, so the only possibilities I can think of are assembly errors or defective chip.
Thanks so much for looking over my layout. Probably an assembly error there is some weirdness going on with the board. I’m going to build out another one. Will update with my findings.
Had a troubleshooting session. Just got myself an oscilloscope but I have no idea how to use it
No idea how to read it or measure the pulse.
I am using a Doepfer LFO on the input and running the output into a 3340 VCO. I am getting a slow clicking sound that seems to be in sync with the internal trigger on the board.
The chip is getting quite hot as well. I checked for shorts and didn’t find any.
I suspect the capacitor isn’t holding the charge. I got a polypropylene 1n cap off ebay. I’ll order a polystyrene one.
The angle of the photo can make it hard to tell, but I have a feeling the longer yellow link to the bottom left of IC2 is incorrectly located. In the layout at the top of the post with grid references, I think o9 and N9 may have become switched.