REPAIR SHOP 

Repair of  ALTO TS115  TRUESONIC - Powered Speaker

Fault: The speaker had stopped working and was completely dead after liquid had got into the vent at the rear.

This speaker has 2 amplifiers - a 335w class D for the Bass driver and a 65w class B for the tweeter, we were unable to get any schematic drawings for this amplifier, however luckily the amplifier is formed basically from three parts based on three chips, so it was just a case of looking up the relevant application sheets and these give all the relevant information.

I asked the customer to just bring in the chassis and it duly arrived in bits, See below the chassis separated from the back cover 

Stripped down the chassis to gain access to the PCB  On initial testing  found the Switched mode PSU was faulty with both switching transistors blown, I did not have the correct replacement transistors in stock, however found a couple of suitable high power Mosfet switching transistors 2SK2610 to use as replacements.   

Installed these new devices reassembled the chassis and powered up - still totally dead, did some homework and found the application sheet for the IR2156S which is the control chip for the power supply circuit, it is relatively straightforward, tested a few of the other components around the IR2156S - all looked good so ordered a couple of these devices, see below a picture of the chip just after it was replaced, note we also removed the 2  big smoothing capacitors and switching transistors to give as much access as possible.

Re -fitted the 2 smoothing capacitors, the 2 switching transistors and re assembled the chassis for testing  

Powered the amplifier up - all seemed to look good, did some testing and left on for a few hours, the amplifier was as good as new and was returned to the customer    

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