7 channel NAD receiver,Need help identifying a suitable cap replacement

[fytonv]

My 7 channel NAD receiver has audio quality and volume issues on 2 of the channels. Sometimes they work and sometimes they don't. Sometimes they're at about half the dB level of the left channels, and then they cut out entirely. Powering off and on the receiver fixes it for a bit.

Without much experience to really know for certain, they only apparent issue I can see is with these electrolytic capacitors on the power supply. Bulging = bad, correct? I'm looking for replacements but I'm unsure what leeway I have with the temp ratings. Are there any other specifications I need to worry about? There's an ocean of capacitors out there but a precise replacement may be hard to find.

Any help would be very appreciated. Thanks!

[andrewsawesomr]

Re: 7 channel NAD receiver,Need help identifying a suitable cap replacement

Yes, bulging is bad. Only the two caps to the right and back are bulging, but I would replace all three. From this datasheet (you can find more datasheets here), you can see that the lead spacing for the old capacitor is 10 mm (sizing diagram, PCB Mount/Snap-in section). Since I can't find a spec for your capacitor on the datasheet, I'll just assume the capacitor needs at least 6.47 amps of ripple current.
Then I just look at Aluminum Electrolytic Snap-In capacitors with ascending prices on DigiKey and Moiser and check to make sure they can handle at least 6.47 amps (or 6,470 mA) of ripple current, and choose that one (I usually only get ones that are in stock).
Here are the ones I found:

https://www.mouser.com/ProductDetail...XjZ4MCahrdw%3D
The replacement capacitor seems to be 63mm tall, so make sure that you can fit 63mm capacitors where the other capacitors are right now.

[fytonv]

Re: 7 channel NAD receiver,Need help identifying a suitable cap replacement

Thank you so much. It looks like the options at Mauser and Digikey around those specs are either too tall or too wide, unless length includes the leads. Does it? These faulty KSC caps are 50mm high and 35mm wide.

[andrewsawesomr]

Re: 7 channel NAD receiver,Need help identifying a suitable cap replacement

It looks like the options at Mauser and Digikey around those specs are either too tall or too wide, unless length includes the leads. Does it? These faulty KSC caps are 50mm high and 35mm wide.

The height does not include the legs

[fytonv]

Re: 7 channel NAD receiver,Need help identifying a suitable cap replacement

Thanks for that info. I'll do some Internet searching to see if I can find something that'll work.

[fytonv]

Re: 7 channel NAD receiver,Need help identifying a suitable cap replacement

What would be the downside or potential real world problems that would arise from using a 10000uF capacitor? Could 2000 microfarads make a difference in an amplifier? Those seem to come in the correct size, like this:

https://www.digikey.com/en/products/...03MELC/2548907

[petehall347]

Re: 7 channel NAD receiver,Need help identifying a suitable cap replacement

they arent bulging ..its the plastic caps that distort with heat ..those caps vent at the bottom . your problem lies elsewhere . and likely the speaker relay . try turning up the vol up sharply whilst its playing up

[fytonv]

Re: 7 channel NAD receiver,Need help identifying a suitable cap replacement

Are the relays the black doodads in the bottom left of the pic? And ... does cranking up the volume trigger the relay to act when its malfunctioning? I haven't tried messing with the volume as a troubleshooting step so I'm interested in better understanding cause and effect.

Thanks.

[petehall347]

Re: 7 channel NAD receiver,Need help identifying a suitable cap replacement

poor contacts in the relay .cranking the vol causes more current flow and helps break through the poor contacts .. it could also be something else like a selector switch or other bad contact .
you could also try tapping the relays to see if any change ..and yes its the black things .

[eccerr0r]

Re: 7 channel NAD receiver,Need help identifying a suitable cap replacement

Does shaking the receiver "fix" the problem too, without powering it down?

Unless those caps are really, really bad (dried out) you would hear audio problems only at high volume. Usually you need a significant cooldown period to change its characteristics as it heats up and cools down.

Also another issue - those capacitors if broken will affect both right and left channels equally since it's in the shared power supply after all... so if this is not happening, agree with petehall347: look elsewhere. I'd look into a cold solder joint on a transistor...

[fytonv]

Re: 7 channel NAD receiver,Need help identifying a suitable cap replacement

Haven't tried shaking it. I'm going to do some bench testing once I put the power supply back in.

I love this forum. "It's not at all what you think it is, it's this series of other things you don't understand." I'll eventually understand . I like the logic that the capacitors are good as they would have an effect on all channels otherwise. I was thinking that it may be the order of channels through the circuit paths. The one thing that remains interesting to me is the FR and C channels are adjacent on the amp board. Each has a separate relay. What are the chances of more than one going bad in exactly the same way?

Anyhow, I've looked pretty closely at all the visible solder points and they "seem" normal. The only thing in the whole box that doesn't look great, besides the bad capacitors that aren't bad, is the thing in the picture below. I have no idea what it is, but it has 7 wires so it must be in line with speaker outputs. I'll try to trace it's path and see if I can test with a multimeter.

Thanks again.

[fytonv]

Re: 7 channel NAD receiver,Need help identifying a suitable cap replacement

I reassembled the receiver and can't seem to reproduce the problem. Sometime it takes a while to materialize.

[fytonv]

Re: 7 channel NAD receiver,Need help identifying a suitable cap replacement

The prob reoccured and cranking up the volume actually fixed it, for now. Good call.

they arent bulging ..its the plastic caps that distort with heat ..those caps vent at the bottom . your problem lies elsewhere . and likely the speaker relay . try turning up the vol up sharply whilst its playing up

[fytonv]

Re: 7 channel NAD receiver,Need help identifying a suitable cap replacement

So I'm getting ready to tear it apart and tackle this potential speaker relay issue, but I'm left with one question.

What are the chances more than one relay will have problems simultaneously?

With more troubleshooting, I do see that messing with volume levels can cure the audio issues temporarily. The amp function of this NAD receiver has two modules, right and left. Left is fine. But all right channels seem to suffer the same symptoms. There are 5 separate relays on the right right amp card. Perhaps this isn't a relay issue and it's something upstream?

Any advice on what I could test with a multimeter would be greatly appreciated.

Thanks everyone.