Hi DIYers, I need some amplifier troubleshooting help.
I have a monitor audio FB-210 subwoofer that doesn't seem to pass input signals.
With it all connected with the cables I've been using with my current sub, the sub recognizes and wakes up to a signal(led changes from red to green when signal is delivered).
It makes a little thump when powered on or off with the switch. I get a very very soft thump when the volume knob is all the way up and turned back and forth a bit. That Is louder when the frequency cutoff is all the way to the high side. Also a super soft hum when the input rca has only the center pin inserted part way.
When rca is plugged in and I touch the other side of the cable , I get no sound unlike my old sub.
I have +/- ~65V on the output transistors and some speaker thump when I touched some of the transistor pins to take measurements.
It has 2 + and 2 - output transistors and 2 smaller balance transistors plus 1 tiny Darlington transistor between them. I removed all and they measured fine outside the circuit.(except I cant measure the Darlington really)
There are 2 driver transistors, one was removed and measured fine.
I got weird measurements for all transistors in circuit but I assume that is heavily impacted by the other components on the board. Some of transistor measurements on diode setting took 3-5 seconds to ramp up to OL from ~1.5V when in circuit but were fine when removed from circuit.
I do not have schematics for the fb210(cant fine them) but do have them for the fb212, which is the bigger brother.
I have not removed the separate input/filter board because its glued to a foam surround.
There is a 6 pin connector between the input and amp boards. The 212 spec says the pins are SG, GND, +15V, GND, -15V, CONT. I measured good grounds and +/-12V on power pins(probably right but I dont have the fb210 spec) Also 10V on CONT and small mV on SG but I may have those 2 backwards.
I'm sure this isnt the best way to report all this ... hopefully someone can help tell me what I need to look at.
I have a monitor audio FB-210 subwoofer that doesn't seem to pass input signals.
With it all connected with the cables I've been using with my current sub, the sub recognizes and wakes up to a signal(led changes from red to green when signal is delivered).
It makes a little thump when powered on or off with the switch. I get a very very soft thump when the volume knob is all the way up and turned back and forth a bit. That Is louder when the frequency cutoff is all the way to the high side. Also a super soft hum when the input rca has only the center pin inserted part way.
When rca is plugged in and I touch the other side of the cable , I get no sound unlike my old sub.
I have +/- ~65V on the output transistors and some speaker thump when I touched some of the transistor pins to take measurements.
It has 2 + and 2 - output transistors and 2 smaller balance transistors plus 1 tiny Darlington transistor between them. I removed all and they measured fine outside the circuit.(except I cant measure the Darlington really)
There are 2 driver transistors, one was removed and measured fine.
I got weird measurements for all transistors in circuit but I assume that is heavily impacted by the other components on the board. Some of transistor measurements on diode setting took 3-5 seconds to ramp up to OL from ~1.5V when in circuit but were fine when removed from circuit.
I do not have schematics for the fb210(cant fine them) but do have them for the fb212, which is the bigger brother.
I have not removed the separate input/filter board because its glued to a foam surround.
There is a 6 pin connector between the input and amp boards. The 212 spec says the pins are SG, GND, +15V, GND, -15V, CONT. I measured good grounds and +/-12V on power pins(probably right but I dont have the fb210 spec) Also 10V on CONT and small mV on SG but I may have those 2 backwards.
I'm sure this isnt the best way to report all this ... hopefully someone can help tell me what I need to look at.