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Old 25th July 2003, 01:59 AM   #1
Keith D is offline Keith D  United States
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Question cleaning of relay contacts or replacement

I have a NAD 7100 reciever I bought off ebay for a good price since one channel was out. I haven't done any real testing other than tapping on parts since I don't have the equipment, but I think the problem is that the speaker switching relay has bad contacts. On the front panel is a A/B button and each set of outputs has one relay, so two relays total. The one channel that's "broken" actually works but I have to turn the volume way up to hear anything, I think the relay contacts aren' touching for that channel. The other channel works, but I noticed there's distortion in it. When I play a test tone, say 100hz, it sounds crackly, but if I push the relay with my fingernail it sounds smooth like a pure test tone should.
So, short of replacing them, can I just spray them with some Caig Deoxit CAIG D5-DS spray? I know that should help, but seeing as how these are probably pretty cheap OEM relays would there be a benefit from replacing them, and most importantly, where do I find good audio relays with good contacts that can handle transients and delicate parts equally well?

Thanks,
Keith
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Old 25th July 2003, 12:30 PM   #2
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Have you tried shorting out the relay temporarily to test the sound...short of getting a new relay...you can try using some contact cleaner and a small cotton swab to clean up the relay...been there done that...once took out the WHOLE channel...to find out the relay was broken..WTF...
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Old 25th July 2003, 08:38 PM   #3
Keith D is offline Keith D  United States
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I will try bypassing the relay but that might screw things up. So far I only have cheap soldering iron and I don't want to have to buy a better one to replace the relays with unless I have to. The sound improved dramatically when I press on the relay to close the contacts tigher. If the cleaner doesn't work and I have to replace them what features should I look for in the new relays? It seems like most of the ones for high level current are cheapos, while the signal level ones are more advanced with better contacts. Where can I get some godo quality relays like the ones used in better amps? I'm sure they wouldn' be more than $5 apiece since the cheap ones are like 50 cents each.
Thanks
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Old 25th July 2003, 09:39 PM   #4
Doh is offline Doh
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Hee hee.

I bought my rotel 980bx the same way through ebay. Fixed it up with some generous help from this forum, and now it works great! In my case, it was a blown rectifier bridge. If it isn't the relay, here's a website that helped me troubleshoot my amp.

http://sound.westhost.com/troubleshooting.htm

As for good quality relays, I think the NAIS relays from digikey are supposed to be pretty good quality. I can't comment on the sonically, but its worth checking out. I don't remember specifically, but around the $5 range. A good look at the old relay should give you all the information on it that you need to replace it, such as voltage, type (DPDT etc).

As for soldering irons, not really necessary to buy a really nice one. I've been using my radioshack soldering iron for 3 years, with a few tip replacements in the interim. Some solder wick should be all that you need to pull the defective part.

Incidentally, the service manual for your unit is available through ebay as well: (just in case it might come in handy)

http://cgi.ebay.com/ws/eBayISAPI.dll...tem=3036791362
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Old 25th July 2003, 11:00 PM   #5
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If you're going to replace the relay, try to get a sealed one. I usually use Goodsky ones, which are relatively cheap but their whole line is sealed. It'll spare you a lot of headaches
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Old 26th July 2003, 02:19 AM   #6
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Hey~~~Anyone tried Solid-State Relays here?? Seems they wun break down~! Other than under dire circumstances...I guess
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Old 26th July 2003, 05:00 AM   #7
Keith D is offline Keith D  United States
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Thanks for the replies. I got a service manual and it's helpful, but as long as I don't do any major repairs or dismanteling I don't think I'll need it. It has every single component rating though in case I have to replace caps or other worn out parts. There's a few problems with the amp I need to fix sometime but they're not critical, stuff like the tuner thinks every channel is strong enough to auto-tune to, and the tone controls probably could use a bypass switch or at least be cleaned. I spent a couple hours yesterday messing with it trying to get the front off but I would have to completely take it apart to do that, fortunatly I can get to both sides of the main board with the relays by only unscrewing the case and bottom panel.
Thanks for that link Doh, I just read through it and I can already think of things to replace! I can tell someone else has worked on the amp because there's a lot of white heatsink paste smeared around.
I'll get right to work as soon as the spray comes, then I'll report back if I still can't figure it out. Expect some questions about the tuner sectionm too, that's not working too great right now, all staticky and weak reception, can't even pick up stations my little clock radio can get. Oh well, it'll be fun upgrading it, that's what DIY is about right?
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Old 30th July 2003, 05:26 AM   #8
Keith D is offline Keith D  United States
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Default DeoxIT worked

Just wanted to let people know the spray worked. The B set of outputs is fixed perfectly, everythings sounds better now and there's no static anymore. The A relay seems to be permanantly broken on the left channel but I don't need two sets of outputs at this point anyways, so no big deal. This stuff really improved the sound, everyone should order a can with your next order from Parts Express. I had been thinking my tuner section sucked, but turns out its actually pretty good, all the static I was hearing came from the dirty relay. Hopefully I'll never need the cold spray I ordered.
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Old 30th July 2003, 06:11 AM   #9
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Default Kids don't try this at home !!!

Solid state relays are meant for switching AC voltages that are not susceptible to distortion. While you can make elegant standby circuits with them (switching the primary of your power xformer) they would distort your audio signal if put into the amps output.

Regards

Charles
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Old 30th July 2003, 11:27 AM   #10
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Thanks for the reply...that would put me away from SS relays for Audio...what about reed relays?? Too low current?? Bounce?? Wonder if there is a No-spoil type of relay that can work with audio...
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