Luxman M-05, 105w class A

KBK · 22nd February 2004, 05:00 PM

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.

sreten · 22nd February 2004, 05:19 PM

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

sreten.

slowmotion · 22nd February 2004, 06:32 PM

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,

neototem · 5th August 2004, 10:00 PM

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

anatech · 7th August 2004, 02:12 AM

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

neototem · 31st August 2004, 03:20 PM

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

ECS21 · 23rd January 2010, 05:51 PM

Hey Anatech, Can you send me the manual? I have One that needs repair.
e4shih@lycos.com

22nd February 2004, 05:00 PM	#1
KBK diyAudio Member Join Date: Dec 2003 Location: The Wilds Of Canada	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. __________________ "Never forget that only dead fish swim with the stream." -- Malcolm Muggeridge. "Truth cannot be brought down, rather the individual must make the effort to ascend to it." -- Jiddu Krishnamurti

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22nd February 2004, 06:32 PM	#3
slowmotion diyAudio Member Join Date: Nov 2002 Location: Norge	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,

5th August 2004, 10:00 PM	#4
neototem diyAudio Member Join Date: Aug 2004 Location: Bois-Colombes	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

7th August 2004, 02:12 AM	#5
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	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

31st August 2004, 03:20 PM	#6
neototem diyAudio Member Join Date: Aug 2004 Location: Bois-Colombes	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

23rd January 2010, 05:51 PM	#7
ECS21 diyAudio Member Join Date: Jun 2004 Location: B.C.	Hey Anatech, Can you send me the manual? I have One that needs repair. e4shih@lycos.com

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