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Strangest problem I've ever had

Ok.
Bought a house.
Paid guy to run wires through the wall for a 3 point system.(too many obstacles & $$ for surround)

Have walls patched and painted. Moved in.
unpacked My Pride and joy B&K 7 channel.

system includes Onkyo sr705, HDMI from cable box to onkyo, connected polk rti12 speakers to B&K with bananas.

turned it all on, incredibly loud buzz snap crackle pop, onkyo shuts off and burnt wire smell fills the air.

Trouble shoot. all wires were hooked up right.
connect speaker wires directly to onkyo one at a time. the farthest one away in the wall shuts off onkyo. I run a new wire on the floor to that speaker. It works.

So it's the wire in the wall, it got compromised some how when the patched wall..?
not so fast.
I have an old kenwood preamp and adcom 2 channel. I hook up "bad wires" in wall directly to kenwood and the speaker works fine. how can bad wire short one amp and work on another???

So then I hook up an RCA pre out channel from the onkyo to the adcom and the same very loud buzz comes on the good speakers.

So the Pre outs on the Onkyo are definitely sending the buzz to both amps... can we assume the Onkyo pre outs are shot.
Million dollar question. Why does the line in the wall short out the onkyo but work on my old kenwood.

So then I test a good speaker line on each output on the onkyo. They all work... I'm doing this with it on, even though I know better... Then I went to connect the bad wires to the onkyo again and I got a spark when I connected the red wire...I've never seen a speaker wire spark off a preamp????!!!!
i've never seen that. I'm going to get a meter and read the line resistance and see if there is a difference with the bad wire.
My concern... If I go get a new preamp, can the bad speaker wire blow it again.
Makes no sense.
That wire was hooked up through the B&K. B&K was connected via RCAs to Onkyo. How could it short the onkyo going back through the B&K.
do we think the onkyo was toasted in the move. If so, how is it that just that 1 line shorts the onkyo and none of the others... too strange
riasillo
almarg's avatar
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almarg
9,670 posts
 
Damage a separate connected preamp? Maybe Al could expand on that.....
Hi Jim,

Assuming that both components have 3-prong power plugs, as you realize the short would result in a direct connection from the "hot" output terminal of the amp to the chassis of both components. What happens from there is obviously hard to predict without knowing the details of the grounding configurations of the components, and other aspects of their design. But depending on the impedances between the chassis of each component and their circuit grounds, some fraction of the current flowing from the amp’s “hot” output terminal will find its way back to the amp’s circuit ground via the Onkyo receiver (being used as a preamp) and the return conductors of the cables connecting the two components. One conceivable scenario would therefore seem to be that a feedback loop is created from the amplifier's output to some upstream circuit point or points, via the Onkyo's grounds, resulting in a large amplitude oscillation, resulting in damage to circuitry in the Onkyo that is designed to handle low level signals.

Or something like that :-)

Best regards,
-- Al
hifitime
715 posts
 
To add more fun, and headaches to it, it sounds like Quietrock 530 has metal inside it. It's under "cutting the panel" on page one. I saw this on a home improvement type of TV show.
riasillo OP
12 posts
 
jea 48.

low voltage guy passed wires around studs in the front between drywall.
I questioned it, not knowing any better and he said it was fine because the drywall guys could see it and work around it. Hard lesson learned.

also cost me a perfectly good receiver.

The electrician came in after, ran electric from existing bank of outlets to spot above fireplace for recessed outlet. His wiring went through studs and was to code as best I can tell... thick yellow wire, that's all I can tell you.

I also had everything plugged into APC line conditioner/surge protector.

Drilled hole today to outside of house, poked wire through and ran it under edge of house out of site, came back in where the cable wire comes. Problem solved ghetto style, I now have a left speaker run... just cost me a $10 for a masonry bit.

Hooked up speakers to onkyo direct, drives them fine... pre outs still shot.

Now i'm off to get a new receiver...what to buy, what to buy...
I was planning on plugging receiver into amp with nothing connected to receiver. fingers crossed when i plug into AMP that the B&K is fine and there is no buzz... then i will connect cable box to receiver and hopefully speakers sign again... any suggestions on way to test amp other than that?

I actually have a little Ipod 1/8jack to RCA adapter. I could plug that into amp and see if amp works right?
riasillo OP
12 posts
 
plugged Ipod into B&K. she sings... music to my ears...

thanks to everyone for help, trouble shooting, learning how to use a meter, etc etc... great community.. thanks again.
jcote
100 posts
 
Quite interesting indeed. Reading Metro/Al's posts helped me understand how to use a meter to test my new cable runs in our garage which was recently wired up for 5.1 channel in ceiling speakers.

To your receiver question, an onkyo 3008 or integra 50.3 are both great receivers at great price points right now.

Disclaimer: I'm selling one of each
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