Denon AVR E400 - Very unwell

[Crystaleyes]

Hi everyone.

Hoping that someone here has some experience with the AVR E-Series

Came across this pristine but poorly unit in a 2nd hand HiFi shop the other day and thought I might learn something in nursing it back to life.

It had a sticker on it stating, "working but only in one (left or right) channel".
Speaking with the shop owner, he said that in fact it would occasionally work in both channels but he doesn't do repairs so it was selling 'as is'.

Anyway, when he went to show me all this, it refused to even start up. When plugged in, it displayed the red LED. Turning it on, the LED flashed green for several seconds then stayed on... And that was that. It wouldn't turn off unless unplugged. No relay sounds, no display appearing on the front.

Regardless, as it was cheap (20 Dollars), I fancied the experience. 🤦♂️


Opening it up revealed a LOT of dust so I carefully dismantled the entire unit and cleaned and visually inspected all the boards. I also verified that the fuse on the back of the display boards was ok.

On the main board, I ESR tested all the electrolytics and verified all the voltage regulators (by applying voltage) and bridge rectifier were working.
Looking closer, the main 3-wire (2 reds, 1 yellow) connector was noticeably loose on this board, so resoldered the three pins to solve that particular problem.

After finding the loose connector I was quietly confident that that might resolve the issue but no. What it did do was give the ability to switch the front LED from green to red and back again, but still no relay action, so no display.

Tried the factory reset I.E. holding the two furthermost left, front-panel buttons as switching it on, but again... No relay, no display.

Obviously, I'll have to look deeper into the manual however I'll probably still disassemble the main boards and verify that the relays are working first.


So... Do any bells ring with anyone? Does anyone know of any other 'reset' options?

If it is true that it had been working in the shop, then hopefully it will turn out to be something straightforward, like the loose connector causing the microprocessor to go into protection mode.



ps. There is no remote control

[Crystaleyes]

An update...

I found all the different reset and error record code options in the manual but still nothing appeared on the display and no relay action was coming from the receiver.


..After looking for relays, there is one which switches on the mains voltage, located on the power supply board, and I think five on the main board (of which at least four seem to be for different input channels).

Clearly the PS board relay should be activated when the on/off switch is pressed on the front panel... This hasn't been happening.

So, after waiting for the LED to stop flashing and become a solid green, I momentarily energised the relay with 20vdc, at which point the display lit up with 'AV SURROUND'.
This lasted perhaps three seconds before disappearing, and the solid green LED began blinkin fast, red.
If I then press the on/off switch, it goes solid red. Pressed again, AV SURROUND appears once more before going blank etc. I can do this ad-infinitum it seems.

At least the display is not the problem. 👍

If I press the factory reset buttons option however, the receiver does indeed do the slow flashing display thing until I release the buttons whereupon it displays' AV SURROUND' once more, and then blink with the flashing red LED. Same with the 'Error History' option.

Considering how the microprocessor appears to be doing the reset thing, surely 'that' has not failed... ?

One last thing is that even though I can keep looping with short appearances of the display, once unplugged, the relay has to be remotely powered once more otherwise we are back to square one. No display and no fast blinking red LED.


I now know that I need to trace the PS board relay switching circuit, it's just that I don't have much spare time right now, however it shall be done.


Any ideas from anyone?