Hi, Working on a Rockford Fosgate T5001bd. Called Rockford to check on schematic. Still in production so they won't release it. The amp has sound with the infrasonic switch on. No sound with it off. I suspect it's an op-amp. Not familiar enough with this model to know which op-amps control the infrasonic circuit. Anyone have an idea or schematic close enough to be used to trouble shoot this problem?
Attachments
Signal passes in one direction. 5V in the other direction. I need to fine where this 5V is coming from.
I didn't think I would have had it if Rockford hadn't released it. Maybe they thought that you were asking for the 5001-bd. See attached.
That looks like it Perry. I have 5 volts on the output pin one of U104. When I lift that pin I have 12volts on the pin. 2.5Volts on the pad.
Short the inverting input to the adjacent output pin and confirm that the non-inverting input matches the shorted terminals. Do this with all terminals soldered to the board.
Shorted pin 3, the inverting input, to pin 1, the adjacent output. Pin 2, the non-inverting input reads -3.5volts.
Sorry Perry. Just trying to understand. Do you mean U104? Pins 3 and 5 are already connected to ground.
To further clarify, I understand I got the pins wrong. I understanding shorting the inverting input to the output should cause the non-inverting input to follow. But in this case, the non-inverting input is tied to ground.
It's OK if the non-inverting input is ground.
If all follow, look for a bad switch, potentiometer or connection.
If all follow, look for a bad switch, potentiometer or connection.
Replaced U100 and it fixed the problem. Don't know why U100 caused U104 to have 5 volts on the output. Now no 5 volts and the amp runs as it should. Infrosonic swith on or off. Thanks Perry for the help and the schematic.
The circuit is DC coupled without the subsonic filter. The DC was blocked when the subsonic filter was used. The gain was amplifying the offset, likely driving the op-amps to where they couldn't function.