View Full Version : What happened to this Nikko receiver?


fdejong
07-28-2009, 06:33 PM
I picked up this Nikko Nr-1219 receiver for a pretty good deal knowing there was something not quite right.

The right channel volume seems pegged at about 1/2 way so that if I turn the main volume down to zero, the right channel is still cranking at about 1/2 volume.

I used deoxit on the volume regulator, and the balance control but it didn't help. I used it as a preamp to another receiver and it was fine, no issues with the right channel at all. So, I think there is a problem with the amp in the Nikko nr-1219?

Here are some photos from the interior. Do the dark stains on the PCB indicate something has burnt here? There were also some black, sooty stains on the inside cover...hmm!

I have a new multimeter, anyway I can go about checking what might be wrong? And then fixing? I am some limited soldering skills...

http://webshare.us/pics/nikko1.jpg
http://webshare.us/pics/nikko3.jpg
http://webshare.us/pics/nikko2.jpg

jdurbin1
07-28-2009, 07:13 PM
Doesn't look like heat damage, not from that side anyway - there'd be some charring of the nearby components if they were running that hot.

Do you have a schematic you can post? And, have you tried running an external preamp signal back into the Nikko amp, or is it one of those that has PRE outs but no PRE ins?

JOhn

fdejong
07-28-2009, 07:54 PM
Good suggestion!

I took the pre-out from another receiver and connected it to the main-in on the Nikko and all seems ok. Sound output from both channels is equal.

So does that suggest something is wrong in the Nikko's pre-amp portion? Earlier I had taken the pre-amp output from the Nikko and fed it into another receiver and it worked as expected....but I will try that again now.

jdurbin1
07-28-2009, 07:58 PM
I would have said it's more likely that this type of problem originates in the preamp (where would the amp be getting signal from if the pre outs are truly zeroed per your first isolation test?) but your retest should clear that up.

Is there a decoupling switch that separates the preamp/power amp sections or just external RCA jumpers?

John

fdejong
07-28-2009, 08:08 PM
Ok, did a retest and I made a mistake in my first test.

The problem is there from the pre-out stage. I suspect I was biased because I saw the dark stain around what I thought was the amplifier section!

So, since it originates in the pre-amp section, and idea how I can track this down? I don't have schematics or a service manual. Any idea where I can find those?

cademan
07-28-2009, 08:10 PM
Your problem is in the preamp portion. The volume pot is a double stack control and it could be the right volume pot that is giving you problems. Use your voltmeter and take readings at both pots and around the connections at the circuit board. Sounds like a broken volume control, or short somewhere around there.

jdurbin1
07-28-2009, 08:12 PM
Try a Google search of the site, if that doesn't turn up any sources you could a request in the Digital Docs forum.

You might try metering the resistances on both sets of pins at the volume control, to see if the pot is working down to zero or close to it on both channels. Measure between each of the center pins and chassis while rotating the control, with the unit unplugged from power.

John

fdejong
07-28-2009, 08:22 PM
Ok thanks.

I just checked out and found the volume pot, and like you said, it's looks to be a double. It's pretty buried.

While there, I noticed this. Possibly a source of the problem? Looks like one melted into the other, there's even a little black smoke mark on the side of the larger cap.

http://webshare.us/pics/nikkov.jpg

reneborg
07-28-2009, 09:54 PM
I just learned something about basic troubleshooting reading this post, and it also represents much of what I like about this site: knowledgeable AND friendly folks!

I also enjoy seeing posts about some of the equipment that I remember from the late 1970s, when I got my first HiFi and had a good friend who worked in a stereo shop. That's where I first heard the 'freaky' :smoke: Ohm speakers as they first came out, and wondered why all the Marantz and Tandberg gear looked more beautiful than the rest ... :music:

ryuuoh
07-28-2009, 10:05 PM
I'm guessing that cap with the soot is leaking. Looks kinda like one I found. Probably unrelated to your volume problem though.

http://www.audiokarma.org/forums/attachment.php?attachmentid=148717&d=1241393988

Tusec
07-28-2009, 10:31 PM
That sooty area is mysterious. It's sooty but the components are clean. I wonder if something burned and a tech basically repopulated that part of the board. This might also explain the long-legged components.

The soot on the electrolytic cap looks like a silhouette of the smaller cap next to it. I'm guessing some third component went up in smoke and the small cap "masked" that area -- kind of like the silhouettes left on walls in Hiroshima.

The right channel volume issue could be completely unrelated to these things though. I agree with the other poster that one side of the pot might have gone bad.

I wonder why a pot would go bad like that though. Maybe DC on it from a leaky coupling cap?

fdejong
09-19-2009, 12:53 AM
Your problem is in the preamp portion. The volume pot is a double stack control and it could be the right volume pot that is giving you problems. Use your voltmeter and take readings at both pots and around the connections at the circuit board. Sounds like a broken volume control, or short somewhere around there.

Wanted to follow up on this old thread.

You were exactly right. It was the volume pot that was the problem. I sourced a Nikko NR-1019 (which had issues) which uses an almost identical volume pot and soldered it into the NR-1219 and it's working :)

Will post some pictures tomorrow. It was sad to cannibalize the 1019 but it cut both channels after about 20 mins of playing, so I figured better one working receiver than 2 broken!

ryuuoh
09-19-2009, 01:01 AM
don't toss the old VR, you might be able to rebuild it.

cademan
09-19-2009, 01:25 AM
I'm glad to have been of some help. Also, everyone here contributed good advice as the problem could have been a multitude of things!

We just have to be willing to accept the facts that our hobby of stereo electronics could lead us into all kinds of directions including letting out the magic smoke! :ntwrthy:

:music: