Luxman M-05, 105w class A - diyAudio
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Old 22nd February 2004, 05:00 PM   #1
KBK is offline KBK  Canada
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Default Luxman M-05, 105w class A

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.
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Old 22nd February 2004, 05:19 PM   #2
sreten is offline sreten  United Kingdom
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Default not exactly subtle

old skool design, checkout the power meters,
with peak hold noless, so a bit more useful,
worth quite a lot in working condition.

sreten.
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Old 22nd February 2004, 06:32 PM   #3
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heh,

I had one of those on loan many years ago,
it tripped the fuse when I turned it on , so I had to use an
extension lead to a 16A outlet down in the basement

If I remember corectly it sounded smoooooth,
but not very dynamic with Kef 107 speakers.

Worth fixing, I'm sure

cheers,
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Old 5th August 2004, 10:00 PM   #4
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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
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Old 7th August 2004, 02:12 AM   #5
anatech is offline anatech  Canada
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Hey KBK,
Cool, the old Lux crew weren't great at troubleshooting. I have a C-05 as well. Great preamp. Need knobs as they were stripping it.
The M-05 is a great unit. Which direction is the offset in? I have the manual as well, I'll have a look.
-Chris
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Old 31st August 2004, 03:20 PM   #6
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the M-05 is back home : wow : that's really heavy
I ordered the service manual, just received it : I will try to put it back to work
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Old 23rd January 2010, 05:51 PM   #7
ECS21 is offline ECS21  Canada
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Hey Anatech, Can you send me the manual? I have One that needs repair.
e4shih@lycos.com
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