Luxman R-115 One Channel Intermittent

DreadPirate · 16th January 2007, 02:11 AM

This is not the ultra monster R-117, but its much younger brother at 80 w/ch. It is a recent thrift store acquisition with this startup problem. When started from cold and volume set low, one channel is completely out. No dc at all on the dead channel, the other is fine and measures 4.5mv at the speaker terminals. If I leave let alone for about 1 minute OR turn up the volume abruptly, some static and crackling and the channel kicks in. For that evening, it starts up nicely, output from both channels immediately after the relay kicks in. Next day, though, same problem, the right channel is dead on startup, eventually wakes up. I've cleaned the volume pot and wiggled everything, it does not appear to be either the volume or any other pot or switch.

pinkmouse · 16th January 2007, 02:14 AM

Blanket resolder, and replacing all the electrolytics is always a good start with a faulty old amp.

DreadPirate · 16th January 2007, 12:14 PM

The unit is of 1988 vintage, is it really necessary to do a blanket cap replacement? As far as resoldering, will reflowing the existing solder suffice or is more involved? What temp would you recommend I do this at?

pinkmouse · 16th January 2007, 12:18 PM

Quote:

Originally posted by DreadPirate
The unit is of 1988 vintage, is it really necessary to do a blanket cap replacement?

Yup, it's worth it on anything over about 10-15 years old.

Quote:

As far as resoldering, will reflowing the existing solder suffice or is more involved? What temp would you recommend I do this at?

Reflowing should be fine. I don't do that temperature stuff, I just have a 20w iron for little stuff, and a 50w for bigger stuff.

Piercarlo · 16th January 2007, 06:14 PM

Quote:

Originally posted by DreadPirate
I've cleaned the volume pot and wiggled everything, it does not appear to be either the volume or any other pot or switch.

Have yet cleaned even the relay contacts? Old relays with oxidixed contact often show itself with the simptoms you described for your Luxman (on channel intermittent or creaky). A cleaning with usual contact polishing sprays may solve the problem.

Try it before throw it... ;-)

Hi
Piercarlo

anatech · 16th January 2007, 06:55 PM

Hi DreadPirate,
Piercarlo has given you the correct answer in most cases. Make sure that no cleaner remains on the relay contacts when you are done, or buy a new relay (best solution).

If you still have problems, resoldering as Al suggested is a very good idea. I would do that as well if I were you.

-Chris

DreadPirate · 16th January 2007, 07:54 PM

I have deoxit, I plan on wetting a strip of cloth, sliding it back and forth between the contact surfaces, then following up with a dry cloth. Is this the best way to clean contacts?

And has anyone encountered the volume control issue on this series of Luxman? What are the symptoms? I have the opportunity to pick up a replacement volume control unit and a set of knobs for $35.

anatech · 16th January 2007, 08:02 PM

Hi DreadPirate,

Quote:

And has anyone encountered the volume control issue on this series of Luxman?

Nope

Quote:

I have the opportunity to pick up a replacement volume control unit and a set of knobs for $35.

It's worth it for the knobs alone.

Follow the cleaning of the relay up with a non residue cleaner. Electrowash 2000 PX would do nicely.

-Chris

DreadPirate · 16th January 2007, 10:09 PM

Sure enough, I was able to duplicate the symptoms by rocking the relay cover. The solder looks good on this board, its one of those vertical ones mounted off the speaker connectors. Tapping around yielded no results, looks very likely its the relay. Am I to guess that this part is not obtainable at this point? Will there be info on it to order a replacement or is the schematic necessary?

anatech · 16th January 2007, 10:52 PM

Hi DreadPirate,
Check out MCM or some other vendors like that.

You can also take them apart and clean them. Desolder and remove them from the board first.

-Chris

16th January 2007, 02:11 AM	#1
DreadPirate diyAudio Member Join Date: Jan 2006 Location: Northern Virginia, USA	Luxman R-115 One Channel Intermittent This is not the ultra monster R-117, but its much younger brother at 80 w/ch. It is a recent thrift store acquisition with this startup problem. When started from cold and volume set low, one channel is completely out. No dc at all on the dead channel, the other is fine and measures 4.5mv at the speaker terminals. If I leave let alone for about 1 minute OR turn up the volume abruptly, some static and crackling and the channel kicks in. For that evening, it starts up nicely, output from both channels immediately after the relay kicks in. Next day, though, same problem, the right channel is dead on startup, eventually wakes up. I've cleaned the volume pot and wiggled everything, it does not appear to be either the volume or any other pot or switch.

16th January 2007, 02:14 AM	#2
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	Blanket resolder, and replacing all the electrolytics is always a good start with a faulty old amp. __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

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16th January 2007, 12:14 PM	#3
DreadPirate diyAudio Member Join Date: Jan 2006 Location: Northern Virginia, USA	The unit is of 1988 vintage, is it really necessary to do a blanket cap replacement? As far as resoldering, will reflowing the existing solder suffice or is more involved? What temp would you recommend I do this at?

16th January 2007, 06:55 PM	#6
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi DreadPirate, Piercarlo has given you the correct answer in most cases. Make sure that no cleaner remains on the relay contacts when you are done, or buy a new relay (best solution). If you still have problems, resoldering as Al suggested is a very good idea. I would do that as well if I were you. -Chris

16th January 2007, 07:54 PM	#7
DreadPirate diyAudio Member Join Date: Jan 2006 Location: Northern Virginia, USA	I have deoxit, I plan on wetting a strip of cloth, sliding it back and forth between the contact surfaces, then following up with a dry cloth. Is this the best way to clean contacts? And has anyone encountered the volume control issue on this series of Luxman? What are the symptoms? I have the opportunity to pick up a replacement volume control unit and a set of knobs for $35.

16th January 2007, 10:09 PM	#9
DreadPirate diyAudio Member Join Date: Jan 2006 Location: Northern Virginia, USA	Sure enough, I was able to duplicate the symptoms by rocking the relay cover. The solder looks good on this board, its one of those vertical ones mounted off the speaker connectors. Tapping around yielded no results, looks very likely its the relay. Am I to guess that this part is not obtainable at this point? Will there be info on it to order a replacement or is the schematic necessary?

16th January 2007, 10:52 PM	#10
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi DreadPirate, Check out MCM or some other vendors like that. You can also take them apart and clean them. Desolder and remove them from the board first. -Chris