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Old 26th January 2014, 02:54 PM   #1
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Default Luxman mk 2 combo

Got the set consist of M-120A, C-120A & G-120 (not mk2) as gift from former Boss who's leaving the country. The set has been idle in the matching Luxman rack for several years due to intermittent sound he suspected the amp has problem. Tested at my home that I found it's the preamp has problem and the amp is working perfectly.

After several minutes of playing there's screeching or static sound on both channels at irregular intervals. The strange sound goes with volume control.I'm not a tech so, completely blank on this. Need your technical opinion or insight to at least I have an overview of the problem when I take it to technician.

Would appreciate any feedback you can share...

Last edited by Ojojunkie; 27th January 2014 at 02:23 AM. Reason: Word spell
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Old 26th January 2014, 03:59 PM   #2
tvrgeek is offline tvrgeek  United States
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Could just be the volume control, could be old caps, could be a bad solder joint.
It takes a tech to figure it out. Blind diagnostics is just a stab in the dark. That was the good old days of gorgeous Lux stuff, so have it checked out. All the electrolytic caps are bad by now. Probably dirty switches and pots.
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Old 26th January 2014, 05:39 PM   #3
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Already did basic knobs test by rotating seems everything is fine, no any sign of dirt in contacts. Not use any contact cleaner and I don't have one. Hope no major problem, have plan to replace the caps. In other thread I read mk 2's C111,C112,C123 & C124 have 2.2uf carps not electrolytic. The model I have at C111& C112 has axial caps with "crossover capacitor" label. Those locations can I put poly caps of same value or only the 2 locations with axial caps.

Thanks for the reply...
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Old 26th January 2014, 07:37 PM   #4
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Sounds like bad transistors in the pre-amp or bad solder joints (or both). Does it care which source you're using? Does it stop if you disengage the tone controls? Is it on both channels?

Bad caps are unlikely.

Cleaning the potentiomters and switches is mandatory before you do any kind of service or troubleshooting. This can be the source of any type of problem. Just regular alcohol will work.
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Last edited by Welcome; 26th January 2014 at 07:40 PM.
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Old 27th January 2014, 02:28 AM   #5
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Thanks to all..

Will do pots cleaning and see what happens. Used aux input only, others not tried yet.
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Old 27th January 2014, 04:19 PM   #6
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Spray the MONITOR and DUBBING switches thoroughly, and work them back and fourth about a thousand times (I'm almost not even kidding). These are usually the culprit of many problems, and I've literally experienced the issue you're having with a similar Luxman model which was caused by a dirty tape monitor switch.

This combo is one of the nicest ever made in my opinion. I hope you get it running well (and keep them!). If necessary I'd recommend spending quite a bit on them.
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Last edited by Welcome; 27th January 2014 at 04:23 PM.
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Old 28th January 2014, 02:37 PM   #7
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Already sent the preamp to a tech for check up and observation. Gave him all your opinions and suggestions as first stage of diagnosis and trouble shooting. Hopefully to hear from him after a couple days and update here, but still I need your insights for other possible parts need to look into.


Thank to all.
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Old 1st February 2014, 04:46 AM   #8
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I got message from the tech, he found the problem on left channel. And it's now running for several hours without any hint of problem but did not mention what's the cause. Will update when I talk to him again.

Have plan to recap the PSU and other signal cap, is it worth to do it? Any recommendation of cap brand and type would appreciate much.

Thanks.
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Old 4th April 2014, 10:27 PM   #9
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Default PSU cap installed

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Old 4th April 2014, 10:33 PM   #10
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Default All installed

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