Long story short, have a powered subwoofer someone gave me years ago. Has bugged me for years and I could not solve the riddle..... It had a hard short but I could not find anything in circuit that was shorted. I am revisiting the project.
I think due to my "testing", I have fried both the front end power transistors. They are reading around 2ohms between legs. They certainly were not before. Anyway, there is a small daughter board by them that appears to be the driver for them. There is no oscillator chip or anything, just a bunch of resistors, diodes, and a single T0-220 bipolar transistor. The collector side of that couples to a couple resistors, then a small component that almost looks like a ferrite bead. It is an axial leaded, shiny black barrel the size of a 1/4W resistor. There are no markings at all on it, but the board shows it as "D11", but I am not sure we can call it a diode or not. It does not show voltage drop, capacitance, or resistance. It is effectively open.
There are a couple zeners on the board, marked with "Z", and a couple others marked with "D". The markings on those were rather odd. They looked just like a zener, clear glass, etc, but not marked like a zener.
307
0
F4
This was on one of them.
I cannot yet be certain what happened to this circuit but I guess i plan to replace what I can find and soft start the amp to see if I can detect what is going on with it. You would think a hard short would be easy to find.....
As well, I determined a main transformer on the board has about 14 pins. one of the pins that connects to the + lead from the rectifier doesn't ring out with any other pins. I never see those damaged but scratching my head on that one.
I think due to my "testing", I have fried both the front end power transistors. They are reading around 2ohms between legs. They certainly were not before. Anyway, there is a small daughter board by them that appears to be the driver for them. There is no oscillator chip or anything, just a bunch of resistors, diodes, and a single T0-220 bipolar transistor. The collector side of that couples to a couple resistors, then a small component that almost looks like a ferrite bead. It is an axial leaded, shiny black barrel the size of a 1/4W resistor. There are no markings at all on it, but the board shows it as "D11", but I am not sure we can call it a diode or not. It does not show voltage drop, capacitance, or resistance. It is effectively open.
There are a couple zeners on the board, marked with "Z", and a couple others marked with "D". The markings on those were rather odd. They looked just like a zener, clear glass, etc, but not marked like a zener.
307
0
F4
This was on one of them.
I cannot yet be certain what happened to this circuit but I guess i plan to replace what I can find and soft start the amp to see if I can detect what is going on with it. You would think a hard short would be easy to find.....
As well, I determined a main transformer on the board has about 14 pins. one of the pins that connects to the + lead from the rectifier doesn't ring out with any other pins. I never see those damaged but scratching my head on that one.