One stereo speaker works off and on. I think it's the receiver. Any fix?
October 6, 2013 4:37 PM   Subscribe

About half the time when I turn on the stereo the left channel speaker doesn't work. If I turn the balance all the way to the left on the receiver, and increase the volume sharply, the speaker comes on. Then I can lower the volume, adjust the balance, and everything works fine till I turn off the stereo. It's the same with all sound sources.

Sometimes the sound works fine when I turn on the stereo, but the left speaker cuts out after it's been playing a short while. Then I can do as above to bring it back.

I'm reasonably sure the receiver is the culprit, because this never happened with my previous receiver, and the volume in the left channel has always been lower in the left channel with this one. Any easy way for me to address it?
posted by lockedroomguy to Technology (10 answers total) 2 users marked this as a favorite
 
Swap the cables connecting the left and right speakers, see if there's any difference, and if not, look into receiver repair?
posted by mikeh at 4:40 PM on October 6, 2013


What receiver is it?
posted by Slinga at 4:53 PM on October 6, 2013


Response by poster: NAD 7155 Receiver. Boston Acoustics A200 speakers
posted by lockedroomguy at 5:02 PM on October 6, 2013


This sounds like a "cold" or "cracked" solder joint to me. "Cold" meaning the solder never flowed properly at one or more of the solder points, leaving a bad connection. "Cracked" meaning, well, cracked - one or more of the solder points has developed a tiny crack, possibly too small for the naked eye to see.

In either case, there's some minimal connection, so when you "gas it up" the electrons are flowing strongly enough that they'll bridge the bad connection, at least for a while.

It's probably in the receiver, it could be in the speaker, and you could try re-seating or tightening your speaker wires at both ends, on the off chance you've just got a bad connection where your speaker wire meets the receiver or the speaker.

If you or a buddy have some experience with electronics soldering, you could take a look with a bright light and a magnifying glass to see if you can find the suspect solder points and then touch them up a bit. Sometimes I don't even bother to try to find the bad point - I just re-solder all likely points in the signal path.

But if neither you or anyone you know has small electronics experience, then there's probably not much you can do. If you can even find a repair shop anymore, it might not be worth the repair, depending on what you paid for it and what the repair guy charges per hour ($50 to $70 with a one-hour minimum wouldn't sound unusual to me.)

If you can't find a repair place or don't feel it's worth it, you could probably sell it for a few bucks on Craigslist or ebay to someone who either has a local repair shop or is willing to take a stab at DIY repair.
posted by soundguy99 at 5:09 PM on October 6, 2013 [1 favorite]


Probably what soundguy99 says but I'd try some electrical contact cleaner before getting rid of it. It comes in an aerosol can with a little straw, so you can get it into crevices. You'll need to pull the balance knob off and maybe lift the lid off the case too. I used the stuff to salvage an decent Harman Kardan amp that I found abandon in a local park. It had basically the same problem.
posted by bonobothegreat at 6:46 PM on October 6, 2013 [1 favorite]


I have had this same problem on several different audio devices over the years (one side cuts out, comes back in only after cranking the volume, then seems to work fine for a while). I never was able to pinpoint the issue, since it's always been in a computer or car stereo or something else that's not easy to get into, but my guess would be a bad solder connection or bad component. Either way, not something you can fix yourself without some electronics experience, and definitely not something easy to fix such as a bad cable or dirty control.
posted by markblasco at 7:11 PM on October 6, 2013


Best answer: This design is 25+ years old.

I doubt it's a cold solder joint. It is contact related, and the contact is probably in either the volume or balance controls.

Test 1 - swap the speaker cables as mikeh says. Just to be sure. If the problem moves with the wires, it's the receiver.


Here's what happens....

Pots (shorthand for the volume and tone and balance controls.... potentiometers) in that era are bakelite substrates coated with carbon-impregnated paint. The paint wears, gets dirty, thinner in places, oxidizes/chemically alters, over time. Some of this is from friction, some from contamination. Sometimes from cat puke, etc.

The 'fix' if there is one, is to get access to these surfaces. I do this in 75 year old radios, sometimes by disassembling them, taking apart the actual pot, and cleaning, dusting, and re-tensioning contact surfaces. Since I don't listen to them toooooooo much, it usually is good for another decade or so. In truly unusual circumstances, I'll design in a new part and/or cannibalize another similar unit. Mostly, I do this with 1970's era Kenwood amps and receivers. They are worth it, IMO. (The KA-7100's are DC coupled and have a bandwidth of 100 KHz. Flat, powerful, brilliant MF's, they are. AND they have lousy switches and pots after 40 years.)

So you have a $40 unit there, according to eBay. This isn't a rare bird you are fixing. Get some contact cleaner from Radio Shack, find a hole that looks like it lets you see the innards, spray it, work it back and forth a bunch, and there's a 90% chance it will improve.

Newer units use digital encoders to send pulse trains to a micro that digitally sets the volume using digital pots. It's easy to do with almost no contact parts. (Last month, I did have to add some capacitors to one to fix a design shortcoming for a neighbor. They aren't perfect, and neither are the designers.) Problems like yours in modern sets are usually actual failures and not so much dirt-related.

Unplug the sucker, first, BTW. Nothing horribly dangerous in there, but unplug it and flip the power switch to ON. Feel free to shoot me an email if you want. Happy to help.
posted by FauxScot at 7:14 PM on October 6, 2013 [2 favorites]


I came in here to say that grit gets into old volume controls, making the connections iffy depending on what position the knob is in, but FauxScot's explained this problem way more eloquently.
posted by Rash at 10:09 PM on October 6, 2013


I've recently had this problem both at home and on my office system, both of which are 70s era amps. I also had it with an 80s era amp. All pretty nice stuff.

Before i even start, and i added this line on preview... Unplug EVERYTHING and pull out EVERYTHING. from both ends, completely unplug it all. Start from scratch and plug in every component one at a time. If you've done this already you can skip this, but seriously everything. Even unrelated stuff. And actually, before you plug everything back in get it down to just one source>amp>speakers(and hell, try a Y cable and your laptop/smartphone/mp3 player. Something really simple that generally isn't used). I've had problems like this be caused by bullshit grounding issues between two different sources connected to an amp.

After that, clarify as to whether it's getting the gain high(with a signal coming in) that makes it cut back in, or is it just wiggling the volume knob a bit. option A is what i thought you meant, option B just means you pull the top off and spray some deoxit in the pot for the volume knob.

That said, Interestingly in my situation it's the same issue in both places with both systems and i still haven't quite tracked it down... but i came up with a temporary solution. What it seems to be is that something is oxidizing/corroding. Check the inputs on the back of the amp. Swapping to a different input actually solved the problem temporarily on one amp, and seemingly permanently on two others. I never spent much time investigating what exactly went "off" about those RCA plugs, but i just couldn't be arsed.(and for the same reason, i will ever use "speaker b" on my home amp, i never actually rewired "speaker a" for one channel)

The only other failure of this variety i've had on a personal system turned out to be that the binding posts on the back of the speakers just... don't hold the wires in that reliably, and they start to get loose over time. The aforementioned current bridging the gap effect(and probably getting one little tiny part of the speaker cable VERY hot and causing it to shift/stick/etc) seemed to fix it for a while until one day it just popped off entirely.

Really though, try the swapping the inputs thing. I can't explain exactly how the hell that worked in any technical sense but just reseating the cables didn't do it. Swapping them somehow did. Maybe something gets screwy in the input selection knob/buttons/switches? On both of them one of the inputs behind a "tape monitor" toggle ended up being the super reliable one, probably because it never got used.

As a closing note, i'll add that i've thrown several pretty damn nice receivers/amps in the "maybe at some point" pile and even sold a couple because of tiresome issues like this i never could, or never got around to tracking down. This isn't an H&K citation or a krell or mcintosh or something. If after a bit of noodling it doesn't seem obvious what the cause is it might just be time for an upgrade.
posted by emptythought at 1:57 AM on October 7, 2013 [1 favorite]


Response by poster: Pretty sure there's a best answer in here somewhere, but I won't know which one till next weekend and will mark it then. Thanks!
posted by lockedroomguy at 5:04 AM on October 7, 2013


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