Help troubleshooting broken Denon AVR-8500

[bo_knows]

If the main speaker relay/s are not activating, there could be a bunch of scenarios:

One (or more channels) amp stages are faulty. They could have DC offset, failure or have a history (in the flash) of short/OC/DC etc.
Are 100% sure the unit has not defaulted or been switched to a pre/processor function? That will keep the main amps off.

Link the S/M and we can help.

One (or more channels) amp stages are faulty.

The ONLY scenario that I could see is that I have somehow shorted center channel speaker cables cause I remove the center channel speaker EVERY time I want to seriously listen to the two channels stereo. I plug the banana ends into the styrofoam block and live it on the floor. I've done that hundreds of times but I'll never do that again.

 

[bo_knows]

Here we go...

Looks like step one, check the analog audio block.

 

[Doodski]

@bo_knows refer to page 35 for the amp modules and the connector(s) pins layout.

 

[Doodski]

@bo_knows also refer to page 150 for the protection diagram.

 

[bo_knows]

 

[restorer-john]

Page 144

 

[bo_knows]

@bo_knows also refer to page 150 for the protection diagram.

Yeah I think troubleshooting starts at page 152.

Page 144
View attachment 214541

Great. Let me get busy, I'll be back in a few to confirm what I've found.

 

[Doodski]

View attachment 214540

What are you trying to communicate with that service mode/diagnostic mode page?

 

[bo_knows]

What are you trying to communicate with that service mode/diagnostic mode page?

Not yet, following John's advice now. It appears that I did not engage the AVR protection.

History appears to be clean.

See attached.

 

[restorer-john]

In that case, I think you have a signal routing issue. Can you connect an on board source? (tuner)

 

[bo_knows]

In that case, I think you have a signal routing issue. Can you connect an on board source? (tuner)

I got stuck with the service path check mode on page 152

I'm not sure if I'm checking the analog path and if everything is ok.

How do I run this test to confirm that analog out is ok?

Please see attached:

 

[Chrispy]

Not sure what you mean? All my inputs are HDMI digital (TV and Oppo). I used oppo analog outputs to AVR analog inputs just to test it to see if the HDMI board went south.

Sometimes you need to manually adjust a particular input's settings for type of source....via input assigment settings....on my older Denon it's setup menu - inputs - input assign and would think yours is same in that respect. What other tests for various inputs/types of inputs have you done?

 

[bo_knows]

Sometimes you need to manually adjust a particular input's settings for type of source....via input assigment settings....on my older Denon it's setup menu - inputs - input assign and would think yours is same in that respect. What other tests for various inputs/types of inputs have you done?

Hi Chrispy,

Thank you for your input but unfortunately for me, this is not the issue. The issue appears to be with some switching/routing of the analog signal to the main amps. When I use HDMI blu-ray input (#3) and the headphones output I can barely hear the music. The same happens when I switch to the RCA analog stage. I think the music that I hear over the headphones is bleeding from somewhere. Also, when I connect the headphone jack, I don't hear the switch clicking as I did in the past.

 

[Chrispy]

Hi Chrispy,

Thank you for your input but unfortunately for me, this is not the issue. The issue appears to be with some switching/routing of the analog signal to the main amps. When I use HDMI blu-ray input (#3) and the headphones output I can barely hear the music. The same happens when I switch to the RCA analog stage. I think the music that I hear over the headphones is bleeding from somewhere.

What does work properly then? Have you performed soft or hard resets? What is your amp assigment setting?

 

[bo_knows]

What does work properly then? Have you performed soft or hard resets?

Everything works but there is no sound over the speakers or headphones.
Yes, I have performed the soft and hard (factory) reset(s).

 

[Doodski]

In that case, I think you have a signal routing issue. Can you connect an on board source? (tuner)

The relays are not engaging so I don't think a input selection is the issue. I'm suspect of the voltage regulation and still suspect of the amp modules as I always am even if the protection routine indicates no errors. Additionally in the case of a pertinent service bulletin we would not be aware of those unless we where a authorized Denon service depot. Checking the voltage regulators requires point to point probing and as you can see @bo_knows the service manual is convoluted. Identifying the relevant connectors and probing those requires a steady hand and serious mind while the unit is powered ON. From what you described it was working fine and then you came home and found it in protection mode?

Try page 88 @ the right side for section, "4.3 Analogue Audio." Check that +/- 7 VDC regulation is operating properly. Use page 45 @ connector N9028 for location of +/_ 7 VDC pins as is detailed on page 88.

There are many voltage regulators in this unit. It could require disassembly to locate the points where one could check for proper operation of them. Additionally we are getting into the need for oscilloscope use now for checking for a signal at the amp PCBs, power supply voltages, voltage regulators and other locations.

Perhaps you would like to send it to Denon Service at this point? There's no sense inducing further faults in this unit if this is a handful.

 

[Chrispy]

Everything works but there is no sound over the speakers or headphones.
Yes, I have performed the soft and hard (factory) reset(s).

Well that's hardly everything works then. What is your amp assigment mode, tho?

 

[bo_knows]

The relays are not engaging so I don't think a input selection is the issue. I'm suspect of the voltage regulation and still suspect of the amp modules as I always am even if the protection routine indicates no errors. Additionally in the case of a pertinent service bulletin we would not be aware of those unless we where a authorized Denon service depot. Checking the voltage regulators requires point to point probing and as you can see @bo_knows the service manual is convoluted. Identifying the relevant connectors and probing those requires a steady hand and serious mind while the unit is powered ON. From what you described it was working fine and then you came home and found it in protection mode?

Try page 88 @ the right side for section, "4.3 Analogue Audio." Check that +/- 7 VDC regulation is operating properly. Use page 45 @ connector N9028 for location of +/_ 7 VDC pins as is detailed on page 88.

There are many voltage regulators in this unit. It could require disassembly to locate the points where one could check for proper operation of them. Additionally we are getting into the need for oscilloscope use now for checking for a signal at the amp PCBs, power supply voltages, voltage regulators and other locations.

Perhaps you would like to send it to Denon Service at this point? There's no sense inducing further faults in this unit if this is a handful.

Yes, you are correct. I expected "more" from the manual and the "service path check mode". I was hoping to at least get some error code(s) or something that would show that there is a hardware malfunction but that was not the case. I will contact Denon on Monday and go from there. I would like to thank all of you for helping and assisting!
It's a great feeling knowing that members around the world care and are willing to help out. This AVR is a great unit when it works. If I was listening to only two channels (stereo), I would build a new system and would remove the receiver. Unfortunately for me, this is not the case. Reality is setting in...

 

[restorer-john]

The problem is the inputs from the various amplifiers are straight into an A/D pin (125) on the main micro.

Me, I would activate protection bypass mode and probe the amplifier outputs one at a time.

The same powersupply that runs the fans, also supplies the 10 speaker relays- are the fans running on any speed on turn on?

 

[bo_knows]

The problem is the inputs from the various amplifiers are straight into an A/D pin (125) on the main micro.

Me, I would activate protection bypass mode and probe the amplifier outputs one at a time.

The same powersupply that runs the fans, also supplies the 10 speaker relays- are the fans running on any speed on turn on?

Hi John,

I can open the lid and turn the unit on to see if fans get activated or move.

There's a service path check for fans but I was not sure how this test works.

Fans apparently have 3 different speeds.