Denon AVR890 - no digital audio - analog OK
Hi folks,
I'm looking at a friends' AVR890, and the problem is that there is (almost) no audio output from digital inputs. We've tried several HDMI and optical inputs. When given an analog signal, the receiver works fine. When given a digital signal, it recognizes and synchs, but seems silent... I say "seems" because, if you crank the volume fully, you can then hear that the audio is coming through, but it very faint. It's not at all noisy or distorted, though. This has been verified with only the digital signal connected from the source - in other words, I'm sure this faint signal is from the digital source, and no analog crosstalk.
I have Googled, and found a lot of people had problems with the headphone jack incorrectly disabling speaker outputs. That does not seem to be the case here, as analog does work fine.
Looking at the block diagram from the service manual, I see that all digital signals run through an EPM240T100C5N, and then the selected digital signal, along with any selected analog signal, run to an ADAU1328. My suspicions would be around the ADAU1328, since that seems like the main place I could seriously attenuate the signal, without losing it entirely or distorting it. Anyone have any experiences with such behavior from this device?
Thanks,
Paul
Hi folks,
I'm looking at a friends' AVR890, and the problem is that there is (almost) no audio output from digital inputs. We've tried several HDMI and optical inputs. When given an analog signal, the receiver works fine. When given a digital signal, it recognizes and synchs, but seems silent... I say "seems" because, if you crank the volume fully, you can then hear that the audio is coming through, but it very faint. It's not at all noisy or distorted, though. This has been verified with only the digital signal connected from the source - in other words, I'm sure this faint signal is from the digital source, and no analog crosstalk.
I have Googled, and found a lot of people had problems with the headphone jack incorrectly disabling speaker outputs. That does not seem to be the case here, as analog does work fine.
Looking at the block diagram from the service manual, I see that all digital signals run through an EPM240T100C5N, and then the selected digital signal, along with any selected analog signal, run to an ADAU1328. My suspicions would be around the ADAU1328, since that seems like the main place I could seriously attenuate the signal, without losing it entirely or distorting it. Anyone have any experiences with such behavior from this device?
Thanks,
Paul
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The other possibility that occurs to me would be a problem with the DSP (ADSP21367), since DSP is only used for digital inputs and not for the analog ones. That part doesn't seem to be easy to come by. Non-stocked at Mouser, doesn't even list at Digi-Key or Newark.
What I'm thinking there is that maybe the DSP is reducing the signals it's processing to near-zero. Any idea if it's possible to disable it?
What I'm thinking there is that maybe the DSP is reducing the signals it's processing to near-zero. Any idea if it's possible to disable it?
FWIW, I did check the diagnostics for the unit, and it's not reporting any problems with the DSP.
I went back to check it out again just to see whether the mute circuit was behaving differently in digital mode, and I found that the analog signals actually weren't going through the DAC as the service manual claimed. Maybe they go through it in some modes, but normally they bypass the HDMI board entirely. So I took a closer look at the mute circuit that affects the DAC output, and found that it was acting weird. Tracing a bit further seemed to indicate a short on the input board (there's a flex cable that carries DAC output and mute signals from the HDMI board to the input board).
Unfortunately, the receiver is built around the input board. You have to remove five other boards and the whole back panel to get it out. After pulling it, I could see that the short was at that board, but the line that was shorted wasn't even used (according to the schematic, anyway). After I pulled the cable from that board's connector, the short went away. Initially I was thinking that one of the muting transistors was shorted, but, since the problem went away with the cable removed, I then figured it was the cable. Put the cable back - still no short. Apparently there was a small bit of metal in the flex cable connector that was shorting the mute signal to +12V (marked +7V on the silk screen). I blew out the connector, re-checked everything, put it back together, and it now works fine.
Unfortunately, the receiver is built around the input board. You have to remove five other boards and the whole back panel to get it out. After pulling it, I could see that the short was at that board, but the line that was shorted wasn't even used (according to the schematic, anyway). After I pulled the cable from that board's connector, the short went away. Initially I was thinking that one of the muting transistors was shorted, but, since the problem went away with the cable removed, I then figured it was the cable. Put the cable back - still no short. Apparently there was a small bit of metal in the flex cable connector that was shorting the mute signal to +12V (marked +7V on the silk screen). I blew out the connector, re-checked everything, put it back together, and it now works fine.
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