Technics SU-V6X Integrated Amplifier
This amplifier had the left hand channel blown. The output devices, drivers, pre-drivers and many associated components including resistors and diodes were destroyed. Finding them all and replacing was a bit of a mission. The circuit is not physically linear and the damages parts were found on all parts of the circuit board. The output devices are the Toshiba 2SA1301/2SC3280 they are now not made and finding originals is very difficult with many fakes available on the 'net; I replaced them with a slightly higher rated pair that I had, the 2SA1302/2SC3281 pair.
With this much destruction it's not easy to know what the cause was but I suspect that one or more of the broken out components on the power control area of the board caused excessive current draw through drivers and/or pre-drivers and over drove the rest of the power amp circuit blowing the output and other parts.
The pre-driver, driver and output circuit is symmetrical, push pull; the bias circuit is included in there also, the bias transistor is under the power transistors and next to the heat sink and that also blew. After replacing all these parts the bias was reset (20mV across the emitter resistors as per the manual) and the amp is now running well. I also cleaned the switches & controls. I have NOT replaced all the capacitors!
These amplifiers have great specs and sound really good and I'm very pleased at how this has turned out.
A little niggle is that the screen printed text on the front panel wipes off very easily, some was worn due to regular use ... volume pot and some wipes off even with a cloth with only water. Oh well.
I would like to suggest that had this unit been checked and serviced (just some resoldering of the broken out joints) it would not have suffered such a catastrophic failure, it is very well built, has good heat sinking and the Class AA computer control works very well.
How does it sound?
Connected to decent speakers and a good source this sounds really good it even has a decent phono stage (it was built at the beginning of the CD era? - 1984 - 1986 apparently) I can highly recommend this amplifier; like most Technics it is well built and seems to have not suffered the soon to come quality savings of the later 1980's.
With this much destruction it's not easy to know what the cause was but I suspect that one or more of the broken out components on the power control area of the board caused excessive current draw through drivers and/or pre-drivers and over drove the rest of the power amp circuit blowing the output and other parts.
The pre-driver, driver and output circuit is symmetrical, push pull; the bias circuit is included in there also, the bias transistor is under the power transistors and next to the heat sink and that also blew. After replacing all these parts the bias was reset (20mV across the emitter resistors as per the manual) and the amp is now running well. I also cleaned the switches & controls. I have NOT replaced all the capacitors!
These amplifiers have great specs and sound really good and I'm very pleased at how this has turned out.
A little niggle is that the screen printed text on the front panel wipes off very easily, some was worn due to regular use ... volume pot and some wipes off even with a cloth with only water. Oh well.
I would like to suggest that had this unit been checked and serviced (just some resoldering of the broken out joints) it would not have suffered such a catastrophic failure, it is very well built, has good heat sinking and the Class AA computer control works very well.
How does it sound?
Connected to decent speakers and a good source this sounds really good it even has a decent phono stage (it was built at the beginning of the CD era? - 1984 - 1986 apparently) I can highly recommend this amplifier; like most Technics it is well built and seems to have not suffered the soon to come quality savings of the later 1980's.