Oh man. I need some help.
I'm a huge fan of L-1 products. I have a couple of their VCAs, and I hope to get more modules in the future. I love the combination of SMD & Through-hole. Extremely awesome DIY products; some of the best kits on the market imo!
I assemble and repair electronics for a living and it's almost bloody embarrassing to be stumped this hard.
It's been a while since I've had something go wrong as well. I'm extremely meticulous, constantly measuring parts upon arrival and sometimes a second time prior to installation. I've shipped nearly 25 Eurorack kits this year, 6 RE-303s, and I've got a final run on 909s upcoming. None of the projects had any issue. But when it comes to a personal project, boom, nothing working properly.
Sorry, my apologizes for the venting!
My L-1 VC ADSR isn't doing so well.
As L-1 kits have SMD parts pre-installed, they tend to assemble quickly and without issue. At least in my previous experience. This started no different. Installation without issue. Powered up, no immediate problems. Was able to trim/calibrate very effectively; <1.0mV on outputs as stated. So far so good!
I use a Mutable Instruments Eurorack tester as my first pass on getting a module up and running. I hooked up my oscilloscope and started inputting gates into the module. The output only outputs a gate. A gate, from 0-5V or so, controlled by the sustain knob. I do not see any Attack, Decay nor Release phases; even with adjustment. When turning up the Attack knob, output will jump from a gate (set by Sustain) to a flat line. Attack LED will stay lit. Upon lowering attack, it'll turn off, and output will immediately jump to a gate. The envelope status LEDs flick by quickly, definitely do not look like some of the videos I've seen in this thread, showing a stepping through the envelope phases.
Both sides generate the same outputs.
I've replaced all the TL074 with others I've got in stock, swapped the NJM13700D with others I've got in stock for other projects. I've only got the pair of THAT340s. I've gone through and double checked the transistors. To my knowledge, I've got my 4s and 6s in the right spots.
Here's a link to images of the PCB.
Here's a link to my personal BOM.
This has been very frustrating and I need to take a break from diagnostics.
The plan is to start getting real pokey with the DMM and start capturing voltages. Any help would greatly be appreciated!
Edit: more details