bxi 2006d

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Good night, I have an Hifonics amp on the workbench i just took off the bottom panel before i exit the shop, ive noticed the powersupply (rail caps) mainly the two end ones seems to have exploded. The owner of the amp told me its the second time that problem as occured.
i know its an overvoltage beyond the rating of the cap 100v (4700uf i think). its a known issue with this type of amp as ive seen on the internet. but i would love to know what causes the rail voltage to go up that high and what fix should be attempted to rectified the problem and keep the voltage stable.
ive added a pic of a board for an example the type im to work on is slightly a different model number, ive exit the shop before taking pictures of it and memorized the model number.
 

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It often happens when the drive for the outputs isn't as it should be. Replace the capacitors and see if the rail voltage is stable (and below the cap's rated voltage). Then drive audio (no load) into the amp. Does the voltage still remain stable?

The 4 transistors across the top of the audio driver board commonly fail. The 470 ohm resistors above the larger driver transistors also have a high failure rate.

Ask the owner if he's running it below it's rated load.

One inductor has a broken tie-down. That could have allowed it to produce a short between windings.
 
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