The nature of this problem is not fully understandable yet. There are a summary of possible reasons that can burn HDMI port. Ground loop connection + electrostatic discharge spark + low quality HDMI cable ground insulation + possible lack of electrostatic discharge protection circuit for HDMI chip in BM cameras.
There are a lot of threads about SDI/HDMI output broken on BM cameras in similar situation:
Totally confused. Faulty Tilta plate fried EVF?
http://www.bmcuser.com/showthread.php?8440Blew the SDI port on my BMCC again...
http://bmcuser.com/showthread.php?9923Tascam DR60D ground loop?
http://bmcuser.com/showthread.php?7859SDI burnout/rolling noise issue BMCC 2.5k EF
https://forum.blackmagicdesign.com/viewtopic.php?t=22659MY SDI input on my BMCC Stop Working
https://forum.blackmagicdesign.com/viewtopic.php?t=25621BMCC SDI problem
https://forum.blackmagicdesign.com/viewtopic.php?t=16745HDMI port on my BMMCC don't works anymore
http://bmcuser.com/showthread.php?21004 ... post254391This is also a quote i got from BMD Support:
Potential causes of SDI failure and how to minimize them.
Isolated Grounds
Isolated grounds may be implemented on a battery plate for safety reasons to allow for isolation between individual devices powered by the plate.
If two devices are connected to individual power connectors AND also have an additional cable between them, there could be the chance of voltage offset.
For example, with an EVF setup, where the camera is on one battery plate power connector, the EVF is on a second plate power connector, and an SDI cable is connected between the devices. Assuming that the SDI connector is internally connected directly to the power negative on each device (chassis ground), then the circuit design will be utilizing the SDI cable shield to provide the common ground connection between the two power supplies. If either the camera or the EVF DO NOT have their SDI shield conductor connected directly to chassis ground, if the SDI cable length is sufficiently long or of poor quality, then the shield in the SDI cable will act as a low-value resistor, and a current will flow through the cable shield between the two devices. You could expect a potential difference measured from one supply's ground to the other.
If the camera and monitor are using either two independent power sources or two power sources on the battery plate where the D-Tap connector may be connected directly to the battery terminals it may have a different negative potential to that of the rest of the power connectors. Ground connection contact bounce may occur and there could be a chance of damaging SDI ports. Contact bounce may also cause all manner of transient voltage spikes to go through the equipment and could cause unforeseen issues.
Prevention
If you have a battery plate with isolated ground supplies, it is recommended to only use it if both the camera and the EVF were powered from the exact same power connector. This can be achieved by plugging a D-Tap multi-tap into the plate D-Tap connector, then connect individual D-Tap cables from the multi-tap to the camera and EVF. That way they are using a common negative connection, with no chance for floating voltage potential variations.
If avoidable SDI interfaces should not be hot-plugged. When setting up or dismantling camera setups make sure that all devices are completely turned off before making any connections to any of the device's inputs or outputs, and any batteries that can be, should removed or disconnected since some battery outlets are always powered.
Electrostatic Discharge (ESD)
This can occur randomly at anytime and can be caused by clothing, packaging, plastics and atmospheric conditions. If you are carrying even a small static charge, you could possible damage sensitive electronic components.
Whilst BNC connectors are designed to minimise contact with the center conductor, if you inadvertently touch near the center contact you could cause a static discharge.
Prevention
The same static prevention measures used when handling sensitive electronic components should be employed when handling video production equipment
As a matter of course discharge yourself when handling a device by touching any large metal object next to you such as a metal table or metal stand or water pipe etc.
SSD drives and the SATA interfaces also do not have high ESD protection.
Always keep any antistatic bags that the SSD drive came in, and always use them for transport and storage of the drive. Use care and try to never touch the drive contacts. SDI ports may also quite sensitive to ESD so static safety precautions should also be implemented when connecting or removing cables.