Hello all. Hoping someone on the forum can help me out with this problem. I recently acquired a SP20E preamp that has nothing but a loud buzz coming from the outputs. I see a couple of potential problems that my/may not be contributing the problem.
1) Appears to be a missing resistor - see photo
2) The the second smaller toroid has two taps tied together 1.9+2.9 but the board input appears to require 9V
Can someone share some insight if the above will have any impact (ie is that resistor location meant to be empty and is the existing toroid acceptable). If these two issues are fine, can you suggest where to look for the cause of the buzz and where to find a schematic. I've reached out to Dan at Tubes4Hifi but not yet received a response. Much appreciated.
1) Appears to be a missing resistor - see photo
2) The the second smaller toroid has two taps tied together 1.9+2.9 but the board input appears to require 9V
Can someone share some insight if the above will have any impact (ie is that resistor location meant to be empty and is the existing toroid acceptable). If these two issues are fine, can you suggest where to look for the cause of the buzz and where to find a schematic. I've reached out to Dan at Tubes4Hifi but not yet received a response. Much appreciated.
Attachments
Do you have an oscilloscope?
Check #1 - power supply ripple.
If you don't have equipment and experience - STOP! Take it to someone who does, an audio repair tech, not an I.T. guy, video guy.
Check #1 - power supply ripple.
If you don't have equipment and experience - STOP! Take it to someone who does, an audio repair tech, not an I.T. guy, video guy.
Nope. But I know you do Chris 😉. If I can't solve it on my own, I'll reach out and drop it off.
- From the guy with the Sugden from hell
- From the guy with the Sugden from hell
Ahh, okay.
Just don't get a shock off that thing please. My first guess would be power supply ripple.
Just don't get a shock off that thing please. My first guess would be power supply ripple.
There appear to be a couple different versions of the board, judging from the old web page, so the missing resistor could just be something that was later eliminated. I suspect the problem is a fried regulator in the high-voltage supply, so that the AC ripple is no longer shunted to ground. I hope Dan will provide you with a schematic.