Two Receiver Dead in One Day

mrjoemorgan

Member
Hey all,

I have been using my setup for about a year without any complication until one day I had two receivers die on me, so below is the curious case of the dying receivers.

My initial setup was a Sony STR-6055 Receiver with Boston CR9 speakers and an Audio Technica lp120 turntable.

The only previous issue I had was one of the channels in the receiver didn't work so I had both speakers connected to the right channel.

All of a sudden when I went to go change a record and put the needle on, the receiver let out a bang, a puff of smoke came out of the top and then a loud humming noise sounded through the speakers. Whilst the receiver turns on, the only sound through the speakers is the loud feedback.

So I go to my local music store and pick up a Yamaha CR840 which has just been restored. Take it home, plug it in, sounds beautiful! Then all of sudden, again when I go to change a record, the sound dies. No smoke or feedback or noise this time but just nothing out of either channel.

Then I take my friends Pioneer Digital Receiver - looks like a 90s black receiver, nothing special and plug in the speakers - we are back up and working! However, if the volume goes above say 25% the receiver shuts down automatically. A little bit of testing tells me that one of the speakers is making the receiver trip, so I rewire it to see if that fixes things, the same story, so I just run one speaker and keep the troublesome speaker disconnected.

So my question/thought is that one of the speakers is causing the receivers to trip/blow - but how does that happen? Or is it something else?

My knowledge in this space is pretty limited but hoping someone can help.

For context, the Sony 6055 produces smoke from the power amp board and the Lower or Upper channel components give me a zero reading on the ammeter. With the Yamaha its gone into protection mode and the SDK chip seems to be dead - zero reading on the ammeter.

Thanks in advance for any help that can be provided.

Joe

PS - Wasnt sure where to best post this so apologies in advance if this is in the wrong place
 
So my question/thought is that one of the speakers is causing the receivers to trip/blow - but how does that happen?
Possibly a shorted voice coil, assuming it isn't a shorted speaker cable. Check the speaker cables for damage.

If you determine a speaker cable isn't damaged, can you measure the resistance of each speaker at the terminals on the speaker?

Post the readings here.
 
Sounds that way to me too. The first receiver had two speakers in parallel on one channel, which right away is half the impedance and twice the load. Add in a shorted or partially shorted voice coil on one woofer, and you've got very low impedance and a recipe for overloading the amp channel.

The Yamaha really should have gone into protection BEFORE the STK module fried, that's what protection is supposed to do, but apparently it didn't work in this case. Bummer.

What exactly are you measuring when you get 'zero reading on the ammeter', and with what device on what setting?
 
@DaveVoorhis / @toxcrusadr - apologies for the delay, I had to wait for the weekend to get some time to have a play around with the gear.

So the non working speaker gives me 1.2 on the reading (although, I think my multimeter might be playing up as when I press the probs together I get the same reading, not zero) whilst on the working speaker, I get 5.3 ish which seems low for an 8-ohm speaker.

Another thing I have noticed today is when I plug the bad speaker into the amp and play music at a low volume (as to not trip the amp) it now sounds like a tin can - no way to describe it other than it sounds like a blown speaker - seems like its just getting worse.

I guess it could be the voice coil like you suggested and maybe I'll open up the speaker today to take a look. If it is, is it worth fixing or is the cost going to outway the cost of finding a new pair of vintage speakers?

Thank again for your continued help
 
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@DaveVoorhis / @toxcrusadr - apologies for the delay, I had to wait for the weekend to get some time to have a play around with the gear.

So the working speaker gives me 1.2 on the reading (although, I think my multimeter might be playing up as when I press the probs together I get the same reading, not zero) whilst on the working speaker, I get 5.3 ish which seems low for an 8-ohm speaker.
Can I assume the first "working speaker" is the non-working speaker?

If so, that's too low. It suggests a shorted voice coil in a speaker element, or possibly -- but unlikely -- some short in the internal wiring of the speaker elements or crossover.

5.3-ish ohms is roughly within the 6 ohms of static aka DC resistance to be expected for an 8 ohms impedance speaker.
 
Can I assume the first "working speaker" is the non-working speaker?

If so, that's too low. It suggests a shorted voice coil in a speaker element, or possibly -- but unlikely -- some short in the internal wiring of the speaker elements or crossover.

5.3-ish ohms is roughly within the 6 ohms of static aka DC resistance to be expected for an 8 ohms impedance speaker.

Yes sorry the non working speaker. I’ll take it apart and see what I can find. If it’s the voice coil how much work is that to fix? Or is it not even worth trying?
 
Yes sorry the non working speaker. I’ll take it apart and see what I can find. If it’s the voice coil how much work is that to fix? Or is it not even worth trying?
There are some speaker elements with replaceable voice coils, but I don't think Boston CR9's have them. You might be able to replace the woofer or tweeter that's failed, but unless you're utterly wedded to the sound of those speakers, I'd treat it as an opportunity to upgrade.
 
There are some speaker elements with replaceable voice coils, but I don't think Boston CR9's have them. You might be able to replace the woofer or tweeter that's failed, but unless you're utterly wedded to the sound of those speakers, I'd treat it as an opportunity to upgrade.
Time to find some Dynaco A25s I think...
 
Possible your meter is not zeroed in and it's showing zero ohms as 1.2 Especially if it's an analog meter. 5.6 for the other one sounds good.

Measuring at the rear terminals you are usually just looking at the woofer's resistance (and maybe an inductor, which has very low resistance). So remove the woofer and disconnect at least one lead from the woofer and check the woofer again. You'll probably find the same thing. Which would explain 'tinny': no bass.

If you replace them, I wouldn't toss them out. Either offer them in need of repair or part them out to get other speakers working. With only one driver bad I'd be tempted to fix them even if it took awhile to find the correct woofer. But that's just me.
 
So I managed to find a tweeter and a woofer on eBay for sale. $30 each. Before I go ahead and buy them, is there anything I should test beforehand to make sure it is the voice coil and not something else? I assume its the woofer and not the tweeter
 
So I managed to find a tweeter and a woofer on eBay for sale. $30 each. Before I go ahead and buy them, is there anything I should test beforehand to make sure it is the voice coil and not something else? I assume its the woofer and not the tweeter
Disconnect and measure the resistance across the terminals of the presumed-faulty tweeter and woofer. If they're rated for 8 ohms impedance (generally printed somewhere on the speaker element itself), their DC resistance will be approximately 6 ohms if they're good, considerably less if shorted.
 
Thanks all - I did the 9 volt battery test on the woofer and got a clum buzz from it. Waiting for my new multimeter to arrive today to do a proper test on both. They might both be cooked!
 
Thanks all - I did the 9 volt battery test on the woofer and got a clum buzz from it. Waiting for my new multimeter to arrive today to do a proper test on both. They might both be cooked!
Do you have kitty cats?
Or puppy dogs?
Or any other animals that like to chew speaker wire?
Check every millimeter of your speaker wires ..
Just to be safe...
And I wouldn't use the same speakers until you're 100% confident that they're in working condition..
I'd be one pissed-off mofo if it's something to do with speaker crossover failure or driver voice coil shorting out. .
At least with the animals you can take preventive measures and assure it doesn't happen again
 
A "clum buzz"?

Should be a click or thump when you connect the battery and another when you disconnect it.

Sorry, clum is a British word for stiff. A very short almost silent stiff buzz. On the working speaker, I get the click/thump when the speaker extends itself.
 
Do you have kitty cats?
Or puppy dogs?
Or any other animals that like to chew speaker wire?
Check every millimeter of your speaker wires ..
Just to be safe...
And I wouldn't use the same speakers until you're 100% confident that they're in working condition..
I'd be one pissed-off mofo if it's something to do with speaker crossover failure or driver voice coil shorting out. .
At least with the animals you can take preventive measures and assure it doesn't happen again

I've tried different speaker wires so I think its internal for sure. I just had my Yamaha and Sony receivers repaired so I for sure want to make sure I have everything fixed before I connect the bad speaker and break everything again. Otherwise I might just retire from vintage audio and buy a violin
 
Sorry, clum is a British word for stiff. A very short stiff buzz. On the working speaker, I get the click/thump when the speaker extends itself.
There shouldn't be a buzz at all, clum or otherwise. Just a click (small speaker) or thump (big speaker).

On the buzzy speaker, try gently pushing the cone by hand. Does it seem gritty or smooth?

(I've been living in GB for nearly 20 years, and I've never heard "clum" before.)
 
I've tried different speaker wires so I think its internal for sure. I just had my Yamaha and Sony receivers repaired so I for sure want to make sure I have everything fixed before I connect the bad speaker and break everything again. Otherwise I might just retire from vintage audio and buy a violin
No don't do that. .. Just find another set of speakers with a good reputation .. and with the current set of speakers completely rebuild the crossovers and do your due diligence with the drivers or just sell them for parts. . And move on to better things.
 
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