Bricksnbeatles
Member known well
Threw this reverb together last night, and instead of getting reverb blended in with the mix control, I get a harsh noise. Clean signal passes thru when active, so the op amps are doing their job…
Checked the voltages, and sure enough the Belton brick isn’t receiving enough power. Thought it was the V-reg letting me down, but I checked the voltages there, and it’s only receiving 5.41v at its input. Realized the culprit seems to be R14— I’m getting a 3.77v drop across it, which is a ~40% voltage drop. Double checked the value both visually and in circuit, and it all checks out. Temporarily removed D2, thinking that could be the cause if it was a bad diode or something, but that measured fine when I removed it, and without it there, the drip across r14 is still 3.77v. I know r14 isn’t really necessary and I could remove it, but it seems that would just put a band aid on the problem. Based on the voltage drop, I would expect to measure ~130 Ω h between the +9v net and ground, which would obviously indicate a partial-short somewhere, and would make for a voltage divider that would give the voltages i’m measuring, but it’s measuring as an open circuit (why it’s not reading as ~2MΩ, given r12+13 I’m not sure, but, anyway…)
It’s been way too many years since I took a math or engineering class, so maybe I’m overlooking something simple, but I’m pretty baffled by this. I could jumper r14 to see where that gets me, but even if that fixes it, it won’t be a satisfying fix because I want to understand first how it’s possible to see a 41% voltage drop across a mere 100Ω in this particular circuit.
Checked the voltages, and sure enough the Belton brick isn’t receiving enough power. Thought it was the V-reg letting me down, but I checked the voltages there, and it’s only receiving 5.41v at its input. Realized the culprit seems to be R14— I’m getting a 3.77v drop across it, which is a ~40% voltage drop. Double checked the value both visually and in circuit, and it all checks out. Temporarily removed D2, thinking that could be the cause if it was a bad diode or something, but that measured fine when I removed it, and without it there, the drip across r14 is still 3.77v. I know r14 isn’t really necessary and I could remove it, but it seems that would just put a band aid on the problem. Based on the voltage drop, I would expect to measure ~130 Ω h between the +9v net and ground, which would obviously indicate a partial-short somewhere, and would make for a voltage divider that would give the voltages i’m measuring, but it’s measuring as an open circuit (why it’s not reading as ~2MΩ, given r12+13 I’m not sure, but, anyway…)
It’s been way too many years since I took a math or engineering class, so maybe I’m overlooking something simple, but I’m pretty baffled by this. I could jumper r14 to see where that gets me, but even if that fixes it, it won’t be a satisfying fix because I want to understand first how it’s possible to see a 41% voltage drop across a mere 100Ω in this particular circuit.
