No sound in hdmi mode unlock flashes on display I get sound in cd

Please see my other answers for Harman Kardon issues. If you can't find them, please respond back here.

Hi, during the last 3 years, my Harman Kardon AVR3600 has worked perfectly, but suddenly i don't know why does my unit only provide sound, and no video.

That I can do, and reset the unit, change the HDMI cable, etc... but still no video. Tkhs

What is the state of the indicated but inidentified digital source? It's trying to tell you to check IT.

I had this exact issue.
I was using the digital 2 input for sound. (Toslink cable from my cpu).

It seems I inadvertantly muted the sound on the pc, and this caused the "unlock" message with the L-R speakers flashing on the display.

I restarted my pc; and then unmuted the sound.
3 seconds later; the L-R stopped flashing and I now have sound on Vid2.

My device is AVR 645, but AVR 745 has the same power regulator board and you could check, if the problem is there.
(AVR 645 volume blue light was not pulsating)
When device is turned on, it shows all display indicators,
no blue light on volume button and no response to any remote or front panel buttons.
Reason for failure:
No 3.3V and 5VD voltages.
I checked bridge rectifier D701 on power regulator board.
One of the diodes was shorted. Also fuse F702 was blown.
Original D701 is KBU6G, but because regulator board is a bit difficult to get out, I decided to use KBU8G. The only difference is Amps rating 6A versus 8A.
Be sure to use SR-5-3.15A fuse to replace F702 and use heat sink paste (you know where) when board is reinstalled.
There is large heatsink in the middle of the receiver. Power regulator board is mounted on the right side of that heatsink. It is down there near the front panel and to get it out you most probably first have
to remove two PCBs hindering access to some regulator component screws. Here are pictures to clarify situation:

Check your audio settings on the main menu of the receiver. The audio input should be set to "auto" Next, make sure you don't have the unit in "6 channel input" mode or "direct" mode. This is usually a small button on the front panel. If you check all this and you still have a problem, post a comment and I will help you troubleshoot some more. Hope this helps

It will only display via component. Your HDMI firmware is either 1.1 or 1.2 and has HDCP issues (High Definition Copyright Protection) it's a firmware problem that has been fixed on all new receivers, not just a HK issue, all receivers! the new version 1.3a and 1.3b have fixed the issue. Unfortunately you cannot update the firmware on the receiver. Hope this explains it for you, sorry! Lot's of angry people out there!!! myself included.

Was a solution ever found for this? I have almost the same problem, except that mine makes a horrible sound through the speakers before it shuts off. However, after an attempt or two, mine usually starts working and sounds fine (I love how this thing sounds!). It seems to happen more when I've let it sit for a week or two. When I use it regularly, it usually works fine. It's almost like it knows when I'm about to give in and replace it... because it will start working again! Maybe I just need to make an effort to use it more....

I also had this UNLOCK message on my Harman Cardon AVR 130.
The reason for this error was - in a hurry I've plugged the optical input into optical OUT! Double check that your connections in the back are correct and hopefully it fixes your problem.

Cheers,
Sergey