Hey guys 
I wanted to build my first zynthian and ordered a v5 kit last weekend. 3 days later it was already here in Zurich 
and yesterday I assembled the parts. Looks and feels very nice so far!
First power on, without an SD-card inserted, the screen flickers lightly for a millisecond (at least some connections seem to work) but it stays black. The raspy has two diodes, red and green, which are on permanently.
Any hints where or how to search for the cause?
Happy weekend 
I’m fairly sure that you can’t do anything without an SD card with a Raspberry Pi, as that contains the OS. If you haven’t prepared the SD card, I would do that bit and then see if there’s still an issue.
I got mine delivered today and forgot I was going to need the SD card so that’s my plan after work.
That was one of my first thoughts as I have also to buy a SD Card later… but a friend confirmed, that a Raspy should give out some messages that it’s trying to boot from somewhere.
Seems more like this problem Zynthian V5 so I’ll check my cables after trying to boot with an SD card.
All my ribbon cables look fine, but I know I’m not very good at not using force so I will have to be very careful, I hope it gets working for both of us with not much effort.
Hi @Marius 
Please, consider that a Zynthian is not an ordinary RPi computer, but a customised music production device, conceived and built around an RPi SBC, with various added digital/electronic components and a device-specific OS, based on a modified Linux Raspbian distribution.
Therefore, while you can expect a normal Raspberry Pi computer to partially behave like a Zynthian synthesiser, if you load the ZynthianOS - but with lower performance, and only after having implemented specific configurations -, you cannot expect a Zynthian music workstation to behave like an RPi computer, especially without its exclusively tailored OS, which is required for starting and driving the connected parts of the instrument.
Cheers!
Hi @Marius & @chipyliyp !
Of course, the V5 can’t boot without the SDcard with the zynthianOS. I thought this was obvious to everyone, but i will add some notes in the building guide to avoid future missunderstanding 
Regarding the Pi, it normally show some text when booting without SDcard and you have an HDMI display connected to it, but not when using the DSI display used by the V5, so it’s totally normal that you see nothing.
Please, follow the instructions on the wiki for downloading and burning the zynthian SD image. Also, note that first boot could take some time until you see the zynthian logo. Don’t be impatient and wait until you see the logo and the “first boot” procedure starts. If you can’t see nothing in the display after 1 min, then something is wrong with the SDcard or the hardware.
Regards!
At the moment, I’m in exactly the position as when Marius started this, just finished building and powering without SD, it looks dead.
Once I get an unrelated Amazon delivery that has been one stop away for hours, I can go out to get the microSD but since I’m not at my proper home, I’m starting to wonder if I will be able to get any sound out… not the best plan so far…
Hated the thermal pad bit, too fiddly, just saying, but I know it’s important
Everything works! It was just the missing card 
A great weekend everyone
Nice to know!
I hope @chipyliyp also got his V5 alive!
Without SD it’s, indeed, dead. Zynthian is a computer and it can’t work without software.
Regards
Yep, mine was fine with a card, I was just out this morning trying to get some cables to get sound out, as I won’t be near my normal gear for at least another week.
I’m terrible at buying anything I like and not using it so trying to avoid that here.
I just added a warning note in the building instructions. I hope it avoids future misunderstandings regarding this subject:
https://wiki.zynthian.org/index.php/Assembling_Zynthian_Kit_V5#BOM_V5_kit
Thanks!