Hi guys I'm trying to fix this powered speaker
I have bass but no treble. The horn speaker works OK but I have no audio signal going into or out of the TDA7293 amplifier chip that drives the horn. The chip has power +/- 24V
I don't appear to have any HF signal coming from the preamp/mixer board, only LF. The signal present LED is on/flashing.
I have a schematic which seems to be the correct one for the main amp but not for the mixer - see attached
For example on my mixer PCB, I don't have SW5 which is referred to on the schematic. Also I don't have U4 (or any place for it on the pcb) which is in the HF audio path. Playing music, I can see an audio signal at pin 1 U2, and I can see audio that looks like bass only on pins 1 & 7 U22 which I think according to the schematic is correct for low frequency path
As U4 isn't present I'm struggling to trace the HF path and there is nothing on FB9 and FB12 where the HF audio should output to the main amp, and these components don't connect directly to the ribbon cable to the main amp as shown on the schematic, they go via resistors R145/R146 to the ribbon cable.
Probably if I had the correct schematic I could work all this out
Richard
I have bass but no treble. The horn speaker works OK but I have no audio signal going into or out of the TDA7293 amplifier chip that drives the horn. The chip has power +/- 24V
I don't appear to have any HF signal coming from the preamp/mixer board, only LF. The signal present LED is on/flashing.
I have a schematic which seems to be the correct one for the main amp but not for the mixer - see attached
For example on my mixer PCB, I don't have SW5 which is referred to on the schematic. Also I don't have U4 (or any place for it on the pcb) which is in the HF audio path. Playing music, I can see an audio signal at pin 1 U2, and I can see audio that looks like bass only on pins 1 & 7 U22 which I think according to the schematic is correct for low frequency path
As U4 isn't present I'm struggling to trace the HF path and there is nothing on FB9 and FB12 where the HF audio should output to the main amp, and these components don't connect directly to the ribbon cable to the main amp as shown on the schematic, they go via resistors R145/R146 to the ribbon cable.
Probably if I had the correct schematic I could work all this out
Richard
Attached Files
