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
You have a shorted wire. You can use an inexpensive multi meter set to ohms to check the resistance between the positive and negative of each speaker wire. If there is no resistance it is shorted (it will either have no connection or a 100% connection, 100% connection = short). Quit using your amps to trouble shoot. Once you know which wire it is then it will need to be fixed or replaced. Better to replace the wire than all your amplifiers.
Quit using your amps to trouble shoot.

Now that is some good advice.
Does sound like a head scratcher though.
It's sounds like you hit your cable with a nail or dry-wall screw when you were patching things up.
Yes, that is a head-scratcher indeed. Some questions and comments:

1)In my experience as an electrical engineer, often when inconsistent and puzzling symptoms are present it turns out either that the problem is intermittent, or there are two different problems that are present at the same time. Not sure what that may specifically suggest in this case, but those are possibilities that should be kept in mind.

2)What kind of speaker cables are you using? Are they by any chance cables like Goertz or Polk Cobra, that have extremely high capacitance which can cause some amplifiers to oscillate?

3)Have you determined where the burning smell was coming from? Was it coming from the speaker wiring, the speaker, the Onkyo, or elsewhere?

Regards,
-- Al
Thanks for responses.

On way to get a meter to test wires.
I do think the wire got compromised . Low volatage guy did his thing, then electrician did his, then sheet rock guys. Someone probably hit that wire...but I also think the onkyo pre outs are toasted.

If I hook up speaker to power amp and receiver to either of my amps from any pre out, plugged into different outlets with nothing else attached, volume on zero = very loud buzz... very loud... none of the pre outs are working right.independent of anything else attached.

like al said, it would seem there are 2 different problems present. I think the burnt smell came from the onkyo.

I used in the wall double coated monocable 12 aug.
I just can't wrap my head around a short in the speaker wire plugged into the power amp, back shorting the onkyo plugged into the Power amp with RCAs. is that possible? wouldn't you expect the power amp to go if anything?
also, if there is a short in the wire, how could the kenwood receiver work on that line. is that possible, like if that receiver doesn't have the same level of circuit protection...