Just as a note : The flyback diodes are used to empty any back-emf from the speakers. These components are also used to monitor the output devices : If you were to observe a hv rail short (if measuring the flyback diodes you discover that you have a short on a diode) it would indicate an output device failure! Very rarely will these diodes fail in normal circumstances. Usually, an output failure is due to excessive heat buildup in the output section. After a few years of use, all amplifiers should be verified for their cooling properties. The output components transfer heat to the heat sinks via 'thermal compound'. This thermal compound will dry up with use and will need to be replaced, eventually. If heat cannot be evacuated efficiently, the output devices will fail.
Do not worry about the back emf : it is just a behavior of a reactive load (speaker) in regards to the output section.
Note : Because the amp has a grounded bridge design, any short with the output section will disable the psu voltages. So, instead of a blown fuse, you will find an unbalanced rail scenario!
Has your tech verified the input board for cold solder connections?
Has your tech verified the CMRR adjustment?
Are the bias voltages correct (@ 330mV)?
joustMember Since 02 Dec 2004
Offline Last Active Nov 19 2015 08:36 AM
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