Ttdfjt

I am trying to get the following RPI3B+ to work. Apparently the machine is booting ok, since I can see it using nmap on my local network:

# nmap 192.168.0.23
Starting Nmap 7.70 ( https://nmap.org ) at 2019-07-09 17:37 CEST
Nmap scan report for 192.168.0.23
Host is up (0.0056s latency).
Not shown: 996 closed ports
PORT STATE SERVICE
111/tcp open rpcbind
139/tcp open netbios-ssn
445/tcp open microsoft-ds
8080/tcp open http-proxy
MAC Address: B8:27:EB:1F:09:2E (Raspberry Pi Foundation)

But I get no display, if I zoom right next to HDMI connector here is what I see:

One of those four components seems to be sideways. Would that explain why I get nothing on the screen ? Is that even fixable ?

While the official Raspberry schematics don't tell a thing about these components we can learn from the picture of the PCB that they are connected to the paired pins 1 and 3, 4 and 6, 7 and 9, 10 and 12 - that's all the differential signal and clock lines.

Since the devices have just four pads (not six) they are not dual-rail clamp ESD protectors, e.g. see here, as these would need to be connected to GND and VCC too.

As they are connected to the paired lines of the differential signals these devices are very likely Common Mode Filters to suppress EMI, e.g. see here.

This is how they are connected in the differential circuit (source). Note that if they are missing or not properly connected the circuit is broken - thus no display is working:

And this is how they look - pretty much like the stuff mounted to the Pi - (source):

Suggested repair: try to resolder the component if you have the equipment and skills to do so. Make sure to not thermally damage the component. Note that high speed TMDS differential signal routing at high frequencies is rather critical. Parasitic loads and asymmetries to the transmission lines may disturb the signals to the point of a failing transmission.

While I can't specifically identify them from this picture where any markings they may have are hidden, that is almost certainly the problem with your HDMI output. If you look at the three that are not sideways, you can see that solder goes from their connectors down to the runs on the board. It appears each one has four connections, and the two presumably necessary connections visible in your picture are clearly broken. This appears to be from damage after manufacture, as there is also solder coming up off of the pads that appears to have separated from the component. As the pads were not lifted from the circuit board, what is visible could be probably fixed with the appropriate equipment, but there is no guarantee that other physical damage isn't present.

What you have is a manufacturing defect called a cold solder joint. There was not enough heat or flux present to properly wet the solder to the component.

This is a very weak joint, and may have passed any electrical test the manufacturer may (or may not) have performed. This can be caught by human or automated visual inspection of the board.

The joint could have broken at any time. However, this is definately a manufacturing defect, and you can likely make a warranty claim on it. I believe that if the joint was properly soldered, the PCB pads/traces or the component would be damaged. Solder joints are pretty strong.

As mentioned in other answers, it's completely possible to fix this. However, on the other side of the component (which we cannot see) are two more solder joints. These may or may not have wetted properly. If they were strong joints, the movement of that component may have lifted the pads/traces from that part of the board. This is okay! They will still conduct, just be careful not to break them. Once you fix it, put a bit of epoxy over it to hold it down, as those pads are no longer performing their mechanical duty of holding the component stable.

Here's a link to IPC 610, which is the standard followed by most manufacturers. That link says "proposed", but it's a good example. I don't think I can link the real thing. Check out the section "5.2.4 Soldering Anomalies – Nonwetting"

IPC-T-50 defines nonwetting as the inability of molten solder to form a metallic bond with the basis metal. In this Standard, that
includes surface finishes, see 5.2.1.

Is that even fixable?

Certainly, if you have the required skills. I would put high-temperature solder flux around the component and heat it up until the tin melts, at which point the component could be moved in position using a needle or a wooden toothpick, preserving the traces.

Another option is to de-solder the component completely and re-solder it back correctly. This would require a thick iron for removal and a thin one for re-soldering. Putting extra flux or tin will help to get all the pads of the component to de-solder at once. For re-soldering, you can glue the component in position and then do the joints, or solder one joint while the component is positioned correctly, then finish the other 3.

Don't try to move the component while it's soldered: tiny traces break easily and are difficult to rework.

Bear in mind that trying to fix anything voids the warranty, so if you're not confident you will succeed, it's best to get the board replaced / refunded.