Troubleshooting F5 - Dennon AVR 4603 hookup - Page 2 - diyAudio
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Old 2nd May 2013, 03:37 AM   #11
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Location: Arizona
Everyone, things appear bit more complicated than a ground loop, it seems.

Tonight I tightened all grounds in the electrical panel. I confirmed good external grounding of the panel through two large copper multi-element cables to earth ground.

I then removed anything plugged in the circuit I was using that I could find.

I confirmed the outletís earth ground. I then set up the following situation:

1. Pioneer TV on standby.

2. HDMI cable from TV to Dennon receiver.

3. Dennon receiver UNPLUGGED (receiving no power).

4. RCA cable from preamp outputs on Dennon receiver to inputs of F5.

5. F5 output to 10 ohm power resistors.

6. Monitored output across one power resistor with scope and voltmeter.

7. Turned F5 on.

I kept my fingers crossed and let things run on longer than ever before, hoping I didnít cook the F5, and took video and tried various settings on the scope to best capture the signal. The signal followed a pattern, and appeared as periodic runs of square waves, at least in part. They must be originating in the TV. Again, they disappear if I unplug the HDMI cable or if I unplug the TV from the wall so the TV receives no power.

I posted the video of the voltmeter and scope on YouTube while I changed between various gains and sweep frequencies on the scope:

F5 Dennon AVR 4603 - Pioneer Elite PRO-111FD - YouTube

What might we be looking at and why are these signals ending up being transferred through the Dennon receiver (not plugged into power) to the F5.

I suspect some additional tests will be to connect the TV to the receiver using component video (without HDMI) and see what things look like. Also might consider trying a different TV or brand of TV.

Just as a reminder from my original post, above, when I do this same setup, but monitor the preamp output of the Dennon receiver across 100K ohm resistors (without the F5) I get 0.000 volts and a flat waveform.

I deeply appreciate any insight that might be offered. Thanks, everyone.
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Old 2nd May 2013, 03:38 AM   #12
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Forgot to mention that everything was powered through a single power strip.
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Old 2nd May 2013, 07:43 PM   #13
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This is looking to me like a failure inside the Denon.
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Old 2nd May 2013, 07:58 PM   #14
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A couple of people have emailed me.

One wondered in I might have a bad HDMI cable allowing cross-talking, perhaps even a short between elements.

Another pointed out that HDMI runs 5V 50 mA and wonders if a signal of that magnitude might not be able to provide enough power to the unplugged amp to energize circuits to some extent, allowing the signal to bleed over to the preamp outputs.

I may try a different cable. But I think it may be more revealing to try a different receiver.
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Old 2nd May 2013, 08:27 PM   #15
bk856er is offline bk856er  United States
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The HDMI in your particular TV also has control capability, so it could be sending out commands or polling external devices even in suspend mode (just speculating here). Do you have a cheap speaker to test/listen to your current minimized configuration with the Denon powered on? Bad HDMI port on either device? Bad HDMI cable?

BK
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Old 2nd May 2013, 08:46 PM   #16
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With the Dennon on and the TV on standby, we see the same problem, as noted in post #1. Thanks for the info on the TV.
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Old 2nd May 2013, 08:56 PM   #17
rif is offline rif  United States
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Did you try unhooking the coax, even if it isn't connected to the denon? Mine wasn't either, and it's quick try and eliminate.
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Old 2nd May 2013, 09:03 PM   #18
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No coax connected to any component at any time during all of this. The TV was used only for playing DVDs.
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Old 2nd May 2013, 11:49 PM   #19
bk856er is offline bk856er  United States
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Very strange indeed. Maybe a good opportunity to build a preamp buffer with DC blocking? Any excuse for a new project is a good excuse, right?

BK
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Old 4th May 2013, 01:41 AM   #20
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Which buffer amp with blocking might you suggest?

I also need to get some better waveforms on the scope to understand better what the signal looks like. Rapid square waves would make it through DC blocking, I would think. More experiments and data over the next couple days, I hope.
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