Igor Wallossek from IL has laid out the likely reason behind the burning and melting of the 12VHPWR adapter. The 16-pin power connector, part of the PCIe Gen 5 suite, can deliver up to 600W of power to a GPU using a single cable, greatly simplifying the setup. Unfortunately for NVIDIA, several users have reported the melting and/or burning of the 12VHPWR connector required to power the GeForce RTX 4090. In addition, board partner models appear to be more prominently affected than their FE counterparts. It turns out that the reason behind all these mishaps is rather straightforward: Cheap soldering.
NVIDIA’s partners have employed a low-quality, manual solder to connect the twelve wires to the 12VHPWR plug. However, as Igor explains it, a much better alternative would be crimping them for a much cleaner layout, as shown below:
Crimping is more durable, keeping external factors such as oxygen and moisture…external. Soldering leaves them open to rusting, in addition to bending and breaking. Soldering employs alloys that tend to form rigid coats vulnerable to tension and tensile load. Furthermore, it has a higher contact resistance leading to an increased thermal load, causing it to turn soft and brittle and break off.
The other flaw boils down to the two-layered design, which causes the cable to bend at the intersection. A proper 90-degree bent wouldn’t have caused the thermal or tensile issues we’ve seen all over Reddit.