Help needed: Denon AVR 5805

[heisenberg_2000]

Anybody out there who is able to help with a question on the Denon
AVR 5805?
Last weekend the unit suddenly stopped output to the speakers.
The part of the movie being watched was not even overly loud.
For several reasons i can not afford right now to bring the unit to
a repair center, plus every time it ends up costing about $ 600.00 .
So i got the repair manual and started to check it out.
I found that the main transformer (which runs the output amps) did not get any power. The power to it is controlled by a relay. The logic circuit controlling the relay have several inputs. Two of these signals are called "POWER" and the second one is called "AC_P.DOWN". The later seems to be used to shut things down.
Does anybody know under what circumstances that signal will be send out?

Thanks Gernot javascript:smilie('')

[bekim]

Hi

You have hefty receiver there..

You can check in your service manual power board schematics and try to figure it out, might be any power circuit which, initiate the relay to fail.
Have you measure the primary of the trafo with ohm meter..?

bekim

[burbeck]

hi,
these things get there shut down signal for the mains from various places, some from the processor, these include power amp overload, dc protect, temperature over load, power supply fault etc,
unless you are familar with all this i would leave well alone untill you finances alows you to send it for proffesional repair
good luck with it

[unclejed613]

I REi repair a lot of denons where i work. denon (and other home theater multichannel receivers) repairs aren't for the faint of heart. 4 things are absolutely neccesary when working on these:
1) a systematic approach to troubleshooting these receivers. gone are the days when a receiver section could be troubleshot as a separate entity. these receivers now have a central nervous system, and the various sections interact through the cpu. protection problems can be due to anything from a shorted output stage to a missing supply voltage, to a loose ground screw somewhere (usually on the back panel)

2)mechanical aptitude. denon especially so, since the larger the receiver, the more complex the 3D puzzle inside.

3) lots of patience. see #2, and the fact that many times, the only indication you get of a problem is shutdown. some manufacturers have a protect message for overcurrent, dc, or power supply problems, but most do not.


4) the proper test equipment. a good meter, an o-scope, a signal source, these are a good start. for troubleshooting cpu problems the scope is essential






more l8r

[unclejed613]

i can tell you some of the common failure items in denon receivers:

3 terminal regulators, such as 7815 and 7915's..... especially the 15 volt ones. denon also uses a 9v rail for some of their DSP and HDMI boards. they drop 32 volts down to 9 by cascading 7818, 7815, and 7809 regulators. these 3 regulators, if they use them are NOT heatsinked and fail often. the +/-15V rails use 7815 and 7915 regulators and these fail often, even though they are heatsinked.
the failure here will be power on for a few seconds and then off. if there is a power status LED it will blink twice a second.

output devices. these are common failure items, but usually when the amps are being pushed at about half power for extended periods. there was also a problem with some of their amps using the wrong bias transistor, which didn't track the output devices well thermally. failure mode, same as above, except the LED may blink once a second or once every 2 seconds.

i recently saw an amp that had ALL of it's amps latched to the rail. the problem was a transistor that is used as a capacitance multiplier on one of the rails for the diff amp (LTP) and VAS stages. if the transistor or the 4.7 ohm resistor feeding it are open, all of the amps latch to the opposite rail and the unit goes into protect mode.
failure mode here, the same as the output devices

relay coils. the power relay can develop a shorted turn or burn open. either way the relay doesn't operate at all, even though your AV_RLY signal goes high.

CPU chip. no response at all to the power switch. you will have +5V standby supply and /PWR_SW signal from the front panel board, but no AC_RLY signal.

standby power transformer or other standby supply problem. you will have no action from the relay, no STBY +5 at the CPU.

if you have a blown AC line (mains) fuse, check the output devices.

generally older denons used the SPEAKER A and SPEAKER B buttons to access the protection override. hold them both down for 5 seconds, or hold them down and turn on the master power button (the one that operates a real power switch)

HTH

[heisenberg_2000]

Thanks to all of you guy's.

First I want to introduce myself (I forget that at my first posting)
Is was born in Germany after WW II, spend some time in the GAF.
Currently, my job is infrared test engineer and I worked on the last Hubble upgrade the WFC III (wide field camera 3) that is 1 of the 2 instruments we made for the Hubble, and we are still working on the James Webb Space telescope (we made all FPA's for the instrument, NIRSPEC, NIRCAM and FGS and the assics ).
Other customers are the University of Hawaii, ESO (European southern observatory) and last not least the government

Besides my work I love cars, high-end video, boating and I don't have enough time for pretty much everything else.

Enough about me. Back to the 5805.

The longer I work (or better investigate) the problem the more respect I got for the people of Denon. The design is just amazing.

As I am following the diff. signals forward and backward thru all the diff. boards and all the internal connections, I came to 2 conclusions, the first one is, that it is impossible to check everything since you can't get to it and once you dismantled the unit you can't test it anymore.
The second is pretty much straightforward just locking at the logic the boards etc and that is, that has to be diagnostic software for
testing the unit. And the connection for that is under the cover on the front panel.
So, for the time beiing, I am keep looking and I will see what I can find out regarding the software.

Gernot

[unclejed613]

the connector behind the front panel is for updating the firmware.

denons that old do not have diagnostic software, just whether the power/standby LED flashes fast or slow. even the newest ones (-09 models for 2009) though they claim to have a test mode, it doesn't work like it says in the service manual, so it must not have got implemented in firmware yet.

any problem the unit has OTHER THAN the standby power supply or the CPU chip will allow the power relay to activate for a few seconds. if the relay doesn't come on at all, it's either your standby power supply (the little transformer and diodes on the board where the power relay is are where this comes from), or the CPU isn't working (requiring a replacement of the DSP board)

[heisenberg_2000]

Hello Unclejed613

thanks for your response, it will give me a good idea what to look for.
Here is what I know so far (besides other bits and pieces). The relay to turn on the main transformer never receives the signal the power up cycle.
I am reasoning that, if something is wrong with the power amps,
and the for the problem to be sensed by the protective circuitry, the power has to be turned on at least briefly.
So I figure that something else is causing that problem.
By the way the speaker are disconnected since the beginning of the issue.
My biggest problem at this time is actually related to the PDF files, I don't have a monitor big enough to keep the display at a magnification large enough to read the "small print", so I end up switching between schematics all the time.

[unclejed613]

next to the power relay should be a small glass diode. measuring from either lead of this diode to ground you should have about 12V dc. if you have 12V dc there, look for a connector on the same board that usually has 4 to 6 wires. they usually have printing on the circuit board indicating the labels of the pins of the connector. one of the pin labels will say +5 S, or +12 S. check the voltage on that pin. it should agree with the pin label. if you have your standby voltage there, go to the ribbon cable going from the front panel to the CPU board. look for pin labels for that connector and measure the pin marked PSW or PWR_ON, or something similar. you should see +5V there that drops to between 0 and 1V when you press the standby/on switch. if you find all of these measurements to be fine, then you need a new CPU board. if any of the first two voltages i mentioned are missing, the standby supply is bad, and you either have a bad standby transformer (the small one on the power relay board) or something else is bad on the power relay board. if you don't have the PSW signal, you could have a problem with the front panel board or again, a problem with the CPU.

i am going to ask the obvious here, but i've overlooked it myself..... did you check the fuses on the power relay board?.... (with power cord unplugged of course).... these units also normally have a "real" power switch in addition to the "soft" switch, and they can go bad as well, killing AC to the power relay board.

[heisenberg_2000]

Again thanks,

I hope that you are not right, with the CPU board. One thing I have to mention is, that everything else works. You can get to all menus and chose from all different inputs etc. So, there is a chance that the CPU is OK.
Tonight I am going to follow you tip and check the diode and the supply voltages.
The fuse close to the relay was the first thing I checked, and the fuse was OK.
On the board above the voltage regulators are 10 fuses and all are fine. I guess that something is preventing the main transformer to start since even HDMI transfer and up converting works.


Gernot