I was given one of these recently, with a blown channel that apparently, no-one, including Luxman, can fix. I have a working channel to work from at least. I was also given the tech book. Anyone interested in a a pic of the schematic?
For those that are unfamiliar with the unit, it is a 90lb, dual mono to the separate channel power cords, fan cooled-back breaker.
It is worth fixing, as everything is there.. that one channel just won't fire up dammit! Well, it does, but with a DC offset. Then it shuts down again. The biasing is way too high. Long story.
I seem to have bit of a history with these units too. For example, a C-05 (matching preamp) came straight from the factory with a situation where no-one from Luxman could make it work for more than a few minutes. For years, everyone in the Luxman tech group took a shot at it. It ended up in the basement of the head of the service department for about 8 years. NIB-DOA, basically. A $3-4k preamp.. screwed. I saw it sitting there one day as I visited. He told me the sad tale. He gave me a shot at it.
I took it home and took the cover off. I then plugged it in. Before turning on the unit I looked around for obvious faults. I saw, in one of the PS rails, there was a fet T0-220 (192?) transistor controlling a bipolar based T0-220 regulation stage. The fet and the bipolar were bent towards and touching each other. "Oh", I sez, "That's not good, it's gonna cause a problem. Thermal runnaways gonna get in there and the PS rail will be way off."
So I bend the two back apart. I turn the unit on and, of course, can't find any fault. That was it. Luxman was defeated on that one for 10 years!
Such is life.
For those that are unfamiliar with the unit, it is a 90lb, dual mono to the separate channel power cords, fan cooled-back breaker.
It is worth fixing, as everything is there.. that one channel just won't fire up dammit! Well, it does, but with a DC offset. Then it shuts down again. The biasing is way too high. Long story.
I seem to have bit of a history with these units too. For example, a C-05 (matching preamp) came straight from the factory with a situation where no-one from Luxman could make it work for more than a few minutes. For years, everyone in the Luxman tech group took a shot at it. It ended up in the basement of the head of the service department for about 8 years. NIB-DOA, basically. A $3-4k preamp.. screwed. I saw it sitting there one day as I visited. He told me the sad tale. He gave me a shot at it.
I took it home and took the cover off. I then plugged it in. Before turning on the unit I looked around for obvious faults. I saw, in one of the PS rails, there was a fet T0-220 (192?) transistor controlling a bipolar based T0-220 regulation stage. The fet and the bipolar were bent towards and touching each other. "Oh", I sez, "That's not good, it's gonna cause a problem. Thermal runnaways gonna get in there and the PS rail will be way off."
So I bend the two back apart. I turn the unit on and, of course, can't find any fault. That was it. Luxman was defeated on that one for 10 years!
Such is life.
sreten.
I've found one for sale, but both output have busted
the previous owner changed the output transistors, but the blowed again within minutes
do you reckon it could be fixed ?
I've no idea of the complexity of the design they used, but think something is wrong in the driver / pre output stage
any idea could help
thanks in advance
the previous owner changed the output transistors, but the blowed again within minutes
do you reckon it could be fixed ?
I've no idea of the complexity of the design they used, but think something is wrong in the driver / pre output stage
any idea could help
thanks in advance
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