After building +30 DIY modules I finally messed one up somehow and I can't figure out how to fix it. The module in question is the V3 Spring Reverb from Befaco.
When I plugin a CV source in either CV IN 1 or CV IN 2 the wet part of the output signal dies and I end up with a completely dry signal, MIX output goes DRY and WET output goes dead. When plugging in the CV source the LED VU meter also dies after a couple of seconds. When removing the CV source everything goes back to normal.
In the build doc there's a calibration step where two offset trim pots are used to decrease CV IN 1&2 bleed through by inputting audio sources as CVs and fiddling with the trim pots. In this step I got the impression that the volume of bleed through wasn't affected at all by how I set the trim pots which I found fishy...
I should also mention that the modules works fine in every other respect.
The schematic is available here: https://befaco.org/docs/Spring_Reverb/S ... ematic.pdf
I tried inputting a fixed +5v source to CV IN 1 (with no audio input, all pots at max but HPF at max) and followed the signal from the jack to the OTA IC4TA. The signal is fine up until R55 100k where the signal becomes negative on the right hand side of the resistor (with respect to the schematic). However, the stuff around the NPN and the PNP transistor before the OTA IC4 is connected to the negative rail so I'm not sure if this is to be expected?
If I'm reading the schematic correctly, the test point TP_1 should be 1v if the CV IN 1 is 5v but I get 0v at TP_1. So it looks like something is pulling the WET part down to zero volts when a CV source is applied to CV IN 1/&2.
My soldering looks OK but I've reflowed every joint could I get to, just to be sure. The PCBs are rather densely populated so I how probably have to desolder some stuff to reach every joint. After reflowing I cleaned the PCBs to get rid of any flux.
I've also tried replacing all the OTAs and Op-Amps but it didn't seem to help. I'm at a loss, all traces looks OK. Could it be that a transistor or diode is malfunctioning?
I've tried reaching out to Befaco but they weren't super helpful. They have their happy ending service and I'll probably use it if everything else fails.
I'm looking for any help with troubleshooting I can get. I've put together a few modules by now but my understanding of the actual electronics involved is inadequate, to say the least. My hope is some kind knowledgeable soul here will read the my description of the problem have a look at the schematic and conclude that "your problem is most likely *here*" but any help is much appreciated.
When I plugin a CV source in either CV IN 1 or CV IN 2 the wet part of the output signal dies and I end up with a completely dry signal, MIX output goes DRY and WET output goes dead. When plugging in the CV source the LED VU meter also dies after a couple of seconds. When removing the CV source everything goes back to normal.
In the build doc there's a calibration step where two offset trim pots are used to decrease CV IN 1&2 bleed through by inputting audio sources as CVs and fiddling with the trim pots. In this step I got the impression that the volume of bleed through wasn't affected at all by how I set the trim pots which I found fishy...
I should also mention that the modules works fine in every other respect.
The schematic is available here: https://befaco.org/docs/Spring_Reverb/S ... ematic.pdf
I tried inputting a fixed +5v source to CV IN 1 (with no audio input, all pots at max but HPF at max) and followed the signal from the jack to the OTA IC4TA. The signal is fine up until R55 100k where the signal becomes negative on the right hand side of the resistor (with respect to the schematic). However, the stuff around the NPN and the PNP transistor before the OTA IC4 is connected to the negative rail so I'm not sure if this is to be expected?
If I'm reading the schematic correctly, the test point TP_1 should be 1v if the CV IN 1 is 5v but I get 0v at TP_1. So it looks like something is pulling the WET part down to zero volts when a CV source is applied to CV IN 1/&2.
My soldering looks OK but I've reflowed every joint could I get to, just to be sure. The PCBs are rather densely populated so I how probably have to desolder some stuff to reach every joint. After reflowing I cleaned the PCBs to get rid of any flux.
I've also tried replacing all the OTAs and Op-Amps but it didn't seem to help. I'm at a loss, all traces looks OK. Could it be that a transistor or diode is malfunctioning?
I've tried reaching out to Befaco but they weren't super helpful. They have their happy ending service and I'll probably use it if everything else fails.
I'm looking for any help with troubleshooting I can get. I've put together a few modules by now but my understanding of the actual electronics involved is inadequate, to say the least. My hope is some kind knowledgeable soul here will read the my description of the problem have a look at the schematic and conclude that "your problem is most likely *here*" but any help is much appreciated.
Statistics: Posted by symmetrizer — Thu Apr 18, 2024 11:15 am — Replies 0 — Views 26