Recently I got a speaker into repair. It died after it went through a power surge. I checked the power supply and found a dual diode package with one diode shorted out. The component was FCH20U10 which were schottky diodes - I replaced it with MUR2060CT which aren't schottky diodes but fast switching diodes(only what I could find). Question 1: Would this be a problem?
After I powered it on the control panel came back to life, but when I passed audio into it no sound was at the output. I investigated the power supply further. I noticed that output of the voltage regulator (+12V) was not very steady. I checked the input of the voltage regulator and it also seems to vary alot from 16V - 17V. Some one advised me to check if there was any AC at the input of the voltage regulator- I checked and there was about 1.5V AC at the input. What could be causing this and is this a problem?

I checked the output of the -12V regulator output it was very steady and the input was very steady as well and there was very little AC voltage present at the input (in the mV range).

Thanks in advance

 

Question 1: Would this be a problem? Its not, but I do not want to read the datasheet instead, so you will have to check if their parameters are equal.

Question 2: What could be causing this and is this a problem?: Your regulator most likely burned. You should check if possible. Also check if the speaker is ok, is there any signal on the input of the speaker?

 

Question 1: Would this be a problem? Its not, but I do not want to read the datasheet instead, so you will have to check if their parameters are equal.

Question 2: What could be causing this and is this a problem?: Your regulator most likely burned. You should check if possible. Also check if the speaker is ok, is there any signal on the input of the speaker?

I changed the voltage regulator still the same.. I'll have to check the input section if there is any audio. One more thing the amplifier IC's part number is scratched out - its one of those 5 pins IC. How could I check whether its burned out?

 

I changed the voltage regulator still the same.. I'll have to check the input section if there is any audio. One more thing the amplifier IC's part number is scratched out - its one of those 5 pins IC. How could I check whether its burned out?

Can you take a picture of it? And give the name and model of the whole device if possible?

 

The model of the sub woofer is Adam Sub7.
Further development, I powered the unit up with the pre-amp board disconnected I could hear a loud switching sound from the power supply board