Luxman r-1050 troubleshooting - diyAudio
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Old 5th July 2014, 07:18 PM   #1
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Default Luxman r-1050 troubleshooting

Hi all,

I have on my desk a Luxman r-1050 for repair. But it doesn't work.. it powers up.. the red indicator led blinks.. there is a click, so the speaker protection is working, and then the led goes out. then nothing

there are no blown fuses, I checked all the caps. there are no signs of burned parts

normally I'm over at the tube amp section and this amp looks anything but the minimal designs that I'm used to.

is there anybody who knows where is should look next?
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Old 6th July 2014, 09:05 AM   #2
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The amp behaves correctly, so it should be working.

Have you checked the speaker selector switch? Do you get sound from the B outputs? From the headphones?

Clean all switches and potentiometers with contact cleaner.

Try all button combinations. Everything should be disengaged (minus the speaker selector, of course). The tape monitor switch can be problematic.
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Old 6th July 2014, 09:43 AM   #3
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Thanks for your reply, I was under the impression that the led indicator shouldn't turn off but should be on after the speaker portion clicks. Anyway I'll try your suggestions and report back. I'll try to post some pictures to.
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Old 6th July 2014, 09:53 AM   #4
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If there is no DC on the speaker feeds then the amp is probably OK, it is probably a bad contact.
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Old 7th July 2014, 08:52 AM   #5
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The LED will blink for a few seconds after start-up and then turn off when the relay clicks. This is normal. If the LED keeps blinking forever and you get no relay activity, the amp is busted and in protection.
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Last edited by Welcome; 7th July 2014 at 08:54 AM.
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Old 7th July 2014, 06:32 PM   #6
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Quote:
Originally Posted by Welcome View Post
The LED will blink for a few seconds after start-up and then turn off when the relay clicks. This is normal. If the LED keeps blinking forever and you get no relay activity, the amp is busted and in protection.
ah the friend who asked me to look at it thought it was the other way around, so with that cleared up I looked at the amp again and....

while testing the amp with the builtin receiver. once I pressed the "fm muting" switch I was blown away by radio noise

I did find a component that looks busted though. see the attachment. don't really understand what happend there.
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File Type: jpg r1050.jpg (77.7 KB, 43 views)
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Old 7th July 2014, 07:43 PM   #7
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Looks fine to me. Just some gunk on it. The big transistor is almost certain to be fine, but the smaller one could be worth replacing. But it's most likely fine as is. If it sounds right, I wouldn't bother.

D102a/b is a dual diode that is known to cause issues. So if you have problems with the power amp, consider checking those out. Replacement is 2x 1N4148 in series.
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Old 7th July 2014, 07:51 PM   #8
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Ok, thanks for your reply, then I won't.

another thing.. I found the service manual which describes the bias adjustments. It seemed like an easy thing to check. Is the amp supposed to be in protective mode during this test?
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File Type: png bias.png (128.6 KB, 34 views)
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Old 8th July 2014, 08:31 AM   #9
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To adjust idle current, remove the fuses indicated.

Your meter should be set to 100/200 mA or equivalent setting. mA - not mV - a lot of people make this mistake.

The amp will not come out of protection when those fuses are out. When you put your ampere meter across the fuse holders (do it with power off - and definitely with some sort of clips), it will come out of protection.

If the ampere meter fuse is blown in your multimeter, likewise - the amp will not come out of protection. Never make any sort of adjustment when the amp is in protection.

Adjust to 50 mA. Note that the variable resistor may be very sensitive. Spray it with contact cleaner or lubricant and wait for half an hour or so before you touch it because otherwise it may behave erratically (unpredictable) and even go open - this will kill the amp.
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Old 8th July 2014, 08:51 AM   #10
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Ah thanks for reminding me to check te fuses... Also one of the alligator clips was broken.. Using a fluke 175 so with auto range not much that could go wrong. Anyway I measure 97mA on the left Chanel! Which raises the question do I need to measure the current on both channels simultaneously?
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