I am attempting to repair a radio shack PA amplifier using the tda7396 chip amp with no output. I do not have a schematic or currently a model number.
I have a good audio signal at pin 2 and a tiny signal on pin 1 (assuming neg. feedback)
I have 18v on pins 3 and 9.
I checked pins 7 and 5. they have good connections to the output transformer. I disconnected the transformer and put an 8ohm load on thinking maybe it was shorted. I did not find any shorts to ground on pins 5 and 7.
I have 9v on pin 8 (standby).
I have .9v on pin 11 (mute) I can not tell from the data sheet if that is normal or not.
I checked pin 4 voltage, it is .6v. The data sheet seems to say that if the self diagnostics pin (4) is showing a fault it will be low. Is .6v low or high? I have a good ground connection on pin 6.
My limited experiance with these is that when then fail they usually short and blow the main fuse. this is not the case.
Befor I replace the chip out of desperation, I am hoping somebody can help me decipher the data sheet and give me some ideas on other things to check. Thanks, Fred
I have a good audio signal at pin 2 and a tiny signal on pin 1 (assuming neg. feedback)
I have 18v on pins 3 and 9.
I checked pins 7 and 5. they have good connections to the output transformer. I disconnected the transformer and put an 8ohm load on thinking maybe it was shorted. I did not find any shorts to ground on pins 5 and 7.
I have 9v on pin 8 (standby).
I have .9v on pin 11 (mute) I can not tell from the data sheet if that is normal or not.
I checked pin 4 voltage, it is .6v. The data sheet seems to say that if the self diagnostics pin (4) is showing a fault it will be low. Is .6v low or high? I have a good ground connection on pin 6.
My limited experiance with these is that when then fail they usually short and blow the main fuse. this is not the case.
Befor I replace the chip out of desperation, I am hoping somebody can help me decipher the data sheet and give me some ideas on other things to check. Thanks, Fred