SC-79 Issue - AVS Forum
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post #1 of 6 Old 08-29-2013, 04:15 PM - Thread Starter
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Just picked up an SC-79 last week. I'm having an issue that I hope somebody with some deep-tissue knowledge can help with.

Configured as a 7.1 system. Ran it through mcacc. Sounded great. Then I grabbed a movie with some transients. (RED, initial scene where the house is attacked.) Volume was set to -17, and the whole thing powered down, with the IPod light flashing. (System is wired with banana plugs where possible, and these speakers have been working fine for 13 years on the previous receiver.)

Tried Digital Safety 1 and 2. No change. Started disconnecting speakers from front to back, retesting each time. Still shut down.

Then I started adding the speakers back in from front to back. NO shutdown until I got to the rear speakers. So I left it all hooked up and tried adding the rears one at a time.With either rear hooked up, no shutdown. With BOTH hooked up, it shuts down.

So, I don't seem to have a stray wire issue. I'm guessing that the issue is that the speaker wire to the rear channels runs about 110 feet, give or take a few. It's 14AWG wire. Yes, a little thin for that long a run. But would that cause this fancy new receiver to freak out and shut off at the first sign of a little noise? Does this sound like a capacitance/inductance issue? Remember with either the left rear or right rear hooked up individually, no problem. It's only when they are BOTH hooked up that it shuts down.

My guess is that I can solve this problem by addressing the wire run. Will replacing with 10AWG wire do the trick, or do i really need to find a way to shorten that wire?

Any advice would be appreciated. Bonus points if anyone can articulate why that amp is shutting off, and exactly what Digital Safety 1 and 2 do.

Thanks!
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post #2 of 6 Old 08-29-2013, 05:09 PM
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My new 77 is hooked up with long runs of 14 wire, 7.1. Runs at loud volumes no problem. Very nice. But not 110 ft maybe 30.

The wire run is too long. I would cut it down. What type of rear speakers are you running?
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post #3 of 6 Old 08-29-2013, 05:30 PM
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Wow thats a long run especially for 14awg and if your rears are 4ohm the issue is worse.
If you have to have runs that long then yeah 10awg.
Curious what were you using before?
Make sure rears are not set to large.
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post #4 of 6 Old 08-29-2013, 06:11 PM
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Easy to test, power the front speakers from Rear panel and see if the problem remains, if so, there's something wrong with your Amp, get it replaced, if not, then maybe the 110ft long is too much or something is wrong with the wires, maybe they are short at some point? Not sure.

Basically, run fronts from the rear panel, then run rear speakers from front and see how it does.

Pioneer Elite Kuro 111FD, Elite BDP-05FD, Elite 72TXV, B&W 805/XTC/M1.
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post #5 of 6 Old 08-30-2013, 07:47 AM - Thread Starter
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The speakers are Kef Uni-Q something-or-anothers. The sit flush in the ceiling and are motorized so they hinge down and face the listening area when activated. Pretty sure they are 8 ohm.

Good idea on connecting the rear amp channels to one of the shorter sets to eliminate the amp. I'll try that. My money is on the amp being fine.

I can probably cut 30 - 35% of the length, with considerable effort. it would require actually running wire outside the house under the siding, since fishing cable up through insulated outside walls is a near impossible PITA. The structure of the house truly leaves no easy solutions.

Any speculation as to specifically what is causing the amp to freak out? I may end up just shortening the cable to fix the issue and moving on, but being an engineer I'm a big fan of understanding root cause. Thoughts?

Oh, and thanks for all the replies. Probably better info here than I would get trying to contact Pioneer.
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post #6 of 6 Old 08-30-2013, 08:14 AM
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Do you still have the AV equipment that was previously powering these speakers and if you hook it back up temporarily does it work fine?
Not sure how you ran the wires but shortening them will help if not i would definitely go 10 AWG on that long of a run also your other AVR may have set your surrounds as small which will greatly reduce the load have you checked to see if the 79 set yours to large.
I have done a lot of installs over the years and so far I have never seen the surrounds shut an AVR of this caliber down unless the wire got pinched ( do a continuity test) or the crossover/ driver was bad you already tested each individually.
I have not installed a 79 yet but it being better than the 68 driving a clients Kef's 205 all 5 of them set to large in a 25 x 17 room I doubt the amp ran out of juice unless defective (can happen).
This replaced an Onkyo 5008 that was simply not powerful enough to drive them and client did not want to go to seperates the rack was already full.
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