So I got a pair of these preamps a while back, pretty cheap. Somewhere along the way, one of them developed a fault, it sounds really thin and trebbly, like all the low end and midrange is being filtered out somewhere. So I started swapping board between the working one and the faulty one to see which board the fault was on, but I didn't get through many of them and all I established was that it wasn't on the scary, densely populated board by the gain knob.
So I try using the working one today and find that's developed the same fault. Or at least, a fault with the exact same symptoms. Last time I used it was ~3 weeks ago and it was working fine then. The only thing that's happened is I did have phantom power on on the interface when I plugged it in today, and it's not inconceivable that I put phantom power into the other one too at some point. So blown filtering capacitor maybe? Looking at the schematic, pins 2 and 3 on the output are connected to the transformer so there wouldn't have been any power flowing across there, the that and everything beyond that should be fine. But that just leaves C3, C19 and C20. C19 and C20 both measure resistance too high for my multimeter, and C3 I don;t think I can emasure while it's in the circuit because there's a path around it that I'm getting the resistance for instead.
So...any idea what the problem could be? Am I on to something here? Or am I attributing the wrong cause entirely to it?
Edit: Schematics
http://recordinghacks.com/pdf/tnc/1073-Main.pdf
http://recordinghacks.com/pdf/tnc/1073-Power.pdf
So I try using the working one today and find that's developed the same fault. Or at least, a fault with the exact same symptoms. Last time I used it was ~3 weeks ago and it was working fine then. The only thing that's happened is I did have phantom power on on the interface when I plugged it in today, and it's not inconceivable that I put phantom power into the other one too at some point. So blown filtering capacitor maybe? Looking at the schematic, pins 2 and 3 on the output are connected to the transformer so there wouldn't have been any power flowing across there, the that and everything beyond that should be fine. But that just leaves C3, C19 and C20. C19 and C20 both measure resistance too high for my multimeter, and C3 I don;t think I can emasure while it's in the circuit because there's a path around it that I'm getting the resistance for instead.
So...any idea what the problem could be? Am I on to something here? Or am I attributing the wrong cause entirely to it?
Edit: Schematics
http://recordinghacks.com/pdf/tnc/1073-Main.pdf
http://recordinghacks.com/pdf/tnc/1073-Power.pdf
