Gigabyte Z370 HDMI Port damaged - ASM1442K levelshifter damaged? - Page 1
Forum section: electronics / repair

author: Hannelore
author_rank: Newbie
timestamp: February 18, 2022, 12:18:13 am
content: Hi,I have a Gigabyte Z370 Gaming 5 board where I often plugedin/out the HDMI cable (unsing the onbaord HDMI port and IGP of intel CPU). I have 1 screen and 2 PCs. I switch the HDMI cable 2-5 times a week from one to the other pc and back.I used an old screen which only supports DVI and VGA. So, I used a HDMI->DVI cable. Sometimes the screen doesn’t show correct colors. After replug the cable it was mostly fixed. I thought maybe its a contact issue.One day this replug workaround didn’t work and the screen showed some red lines. After some replug tries the screen doesn’t show anything anymore (no signal). The Screen was not dead but this read lines stay also if nothing was plugged in and the “No Signal” messaged was shown. So I took the screen apart, give it a clean and tested it again. Screen was ok again and works on other PC. But since then the HDMI Port of the other PC where all started (Gigabyte Board) is deadI had a closer look on this board. The board has a ASM1442K chip and 1x HDMI and 1x DP portThe DP port still works while the HDMI doesn’t. Idk if both port use the ASM1442K levelshifter. If yes this would mean that the level shifter works for DP but not HDMI. I had a look into the Datasheet and did some measurements and somehow the HPD_Sink seems to be connected only to HDMI Port and not to the DP Port. According to the Datasheet the HDMI Connector use an internal pulldown resistor.Any idea whats damaged here? Maybe HPD_Sink input damaged and therefore no HDMI detection while DP is still functional?I also figured out that I always get continously electric shocks if I touch the HDMI Cable (metal) from PC and a GND source like (power supply from monitor, GND point on the motherboard etc). It's not only one short shock, there are many shocks as long as I hold the cable and GND. There are also sparks if I plugin the HDMI cable. But this sparks seems to be on every PC and every screen... seems somehow normal. Maybe something wrong here?Im in fear now that I will damage my last port on this board with cable switching. Is there a save way to switch a DP/HDMI cable?Update: Update: I did another measurement. I measured the differential between GND of the HDMI Port and the GND of the Monitor. in DC mode I only get fluctuating mV .. nothing to mention. But if I measure in AC mode I get a differential of 120V!!!!!! (here we have 240V AC). So means if I connect my Monitor with the PC Mainboard it has to handle a 120V AC difference? Wont this damage maybe all my other Hardware. How it comes that there or so high differentials in GNDs. And why is there a 120VACvalue on hardware which only runs with ~12VDCLink ASM1442K:https://www.asmedia.com.tw/product/eCfYQ4DrGEhz0SXd/647yQ43xZ8UgBRj7Datasheet:https://html.alldatasheet.com/html-pdf/1132349/ETC2/ASM1442/1173/10/ASM1442.htmlUpdate: Seems it was a defect SmartHome Plug. I compared the ground pin of the power sockets in the room and there was a 120V difference between the socket on the one side to the other side of the same room!!! So the PCs was connected to the one side and the monitor to the other side of the room and it seems therefore I had a 120V difference on GND and sparks if connecting HDMI.Later I found out that the 120V on GND comes from the smarthome Plug which was on the side of the room. I removed the smarthome plug and it was back to 0V. So yey. Seems the smart home plug damaged my HDMI Port ☹I also did some measurements on my other devices which use LAN, HDMI etc. to connect two different devices with own power supply. Every device which uses the Ground from the socket was fine. Every device which uses only two phases and no GND hat some potential difference. But currently 50V difference was the maximum I found (TV <-> DVD Player).I think the 120V damaged it and it seems to be no chance to repair it?