Denon DNS3500 screen fault

No display is usually caused by ZD903, it is a surface mount diode on the underside of the power supply board, a tiny little thing, this is a 2.4 volt zener diode, care is required when removing it, but you can fit a real 2.4 volt zener diode on the underside of the board, the cathode is to the right with the diode position closest to you,  I used a 2.6 volt as that is what  I had to hand working no problems.good luck and don't forget to disconnect the unit from the mains supply before working on it, or you will have problems also make a note of the direction of the ribbon cables checking on what side the blue bit is before disconnecting them, it will save you a lot of time and trouble. good luck, kr Pete

It does amaze me when I read on here how people go under the hood of a high voltage amplifier or a sophisticated bit of electronic kit which cost hundreds of pounds to have a poke around with no previous knowledge or experience of repairing such pieces of equipment and expect to some how fix it   

You could have saved yourself a lot of bother (and now money) by just giving it out to a Denon authorised service who would have not only sorted out the problem but also give it service and software upgrade if needed. I'm not sure how old your unit is but is it still under warranty? Silly question maybe but I thought it best to ask...

I think you've learned a valuable lesson from your tinkering but I hope you get the unit sorted out. Good luck!