Hi everyone,
I will check for solder bridges and get some pictures and voltages tonight, but here are the facts so far:
My LED pulses in time with the rate knob. TR1 is affecting the on/off time for sure. TR2 doesn't seem to be doing anything, and I only have clean signal coming through the circuit. Is a solder bridge the most likely culprit? I used TL072s per the BOM by the way.
Thanks,
Bret
Well, I have found one bridge already. If you're looking at the right legs of C4 and R5 from the top of the board, the flip the board over, you can see that those pads are bridged with a big blob of solder. I'll go ahead and fix that tonight. But can someone tell me what that is essentially doing to the signal? Always hoping to learn more.
Looks like C4 & R5 are in parallel, so the ends of each should be tied together. However, if the blob is big enough, it could be grounding the signal at that point, sucking out the signal that's meant to go to the filter sections, which would explain the 'clean, no phasing' phenomenon.
Thanks Jason, that makes sense. I saw that on the schematic as well. When I compare that to the layout though, having those right legs bridged looks like that lets pins 1 and 2 of IC1 connect directly to each other without going the C4 and R5. Those are the output and inverting input, from what I can tell from the datasheet. What would that cause?
Fixed! That solder bridge at the junction of C4 and R5 was allowing pins 1 and 2 of IC1 to connect for sure, meaning no amplification was happening, according to the electronics instructor at work who helped me check this out under one of their massive magnifying glasses in the lab.
Sounds awesome! Build report to come soon.
Awesome! glad you got it worked out. This is a really great sounding circuit.
Thanks! I played with it a bit more this weekend. You are right, it sounds really cool. I would have thought I had test it in darkness or something, but it worked well regardless. What can I say, it's my first optical circuit. And ironic that I finally finish it right as your fabbed version comes out! ;)
I'm already working on the enclosure. Keeping my fingers crossed it works as expected off the bat and doesn't require a round of debugging and re-prototyping.