Denon AVR-X1000 MCU Shorted

[R_J]

Re: Denon AVR-X1000 MCU Shorted

The headphone audio comes from the amp FL & FR amps, Can you access BN501 and touch pin 1 (FL) or pin 9 (FR) with your finger, there should be a buzz in the headphones on that channel if the amp is working.
What are you using for ground, as the chassis might not be at "A" ground.

[mmartell]

Re: Denon AVR-X1000 MCU Shorted

You are right I do hear hum AND audio from each channel by touching those pins.

I redid the readings with D_Ground and they are the same. D_GROUND ohms out with chassis ground.

[budwich]

Re: Denon AVR-X1000 MCU Shorted

that's sounds like a preamp problem then.
I used a cd with 1khz test tone (actually it had choices), input that signal and then traced the input with a scope to see where it disappears or went noisy / dc offset or otherwise.
Crown doesn't shut down for DC as it was a DC300... :-) not nice for speakers though.

[R_J]

Re: Denon AVR-X1000 MCU Shorted

Looks like the audio is selected by IC891 and fed to the amp

[budwich]

Re: Denon AVR-X1000 MCU Shorted

some more "ramble" from me... :-)
IF you look at the amp stage, at Q5x05/06, the circuitry around them is "mirrored". Of course, I know nothing about things like "push / pull", class A, etc... but IF the rails are "significantly different", then the "mid point" of the design which appears to monitoring as the DC detection point is going to be "non zero". I don't see much adjustment in the area so it has to be somewhere else. I think this is your problem. The dc offset is greater than it should be.

[mmartell]

Re: Denon AVR-X1000 MCU Shorted

I'm going to pull the amp board and go over it since there are a limited number of voltage checks I can do on the running amplifier section.

Incidentally, what should the channels look like as they leave the HDMI board (before amplification) ? If I put the meter on them I measure about 6v dc and basically no AC component. Seems strange and yet if I touch them with something I can hear the channel (with much noise) in my headphones...

[mmartell]

Re: Denon AVR-X1000 MCU Shorted

Had another look at this recently and the real problem here is more insidious than an amp problem.

In my previous post I was asking what the signals should look like before they go into the Preamp because I was suspecting there may be nothing there to be amplified.

Turns out the volume IC (IC891) is not passing anything on as its control lines to the cpu have gone high. What should be 33 ohm resistors on the SDA and SCL lines controlling the volume ic are in the mega ohms.

Due to the fact this board came with a shorted cpu it's likely the faults on the signal lines are numerous. I may try replacing those resistors but failing that I'd consider this one unrecoverable.

Thanks to RJ and budwich for indulging me.