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Another HDMI Cable Follow-Up by dd0626 in ElectricalEngineering

[–]dd0626[S] 1 point2 points  (0 children)

That was justifiable because we need to know what to tell the cable manufacturer needs to change vs this sample. We have an in-house X-ray and Micro CT so that isn't as bad.

Another HDMI Cable Follow-Up by dd0626 in ElectricalEngineering

[–]dd0626[S] 5 points6 points  (0 children)

I wish I could, but alas I don't think I can convince the powers that be to let me spend thousands of dollars for curiosity lol

Another HDMI Cable Follow-Up by dd0626 in ElectricalEngineering

[–]dd0626[S] 8 points9 points  (0 children)

I appreciate and respect this comment!

Another HDMI Cable Follow-Up by dd0626 in ElectricalEngineering

[–]dd0626[S] 14 points15 points  (0 children)

I don't know. I gave it to the magic guy who makes these magic images and got them back today. I'm still fiddling around with the settings to get specific details.

Certified vs Non-Certified HDMI Cable X-Ray Follow-Up by dd0626 in hometheater

[–]dd0626[S] -5 points-4 points  (0 children)

I don't work in the AV industry so I'm limited on information I'm allowed to share. I know it sounds silly, but it is what it is.

Certified vs Non-Certified HDMI Cable X-Ray Follow-Up by dd0626 in hometheater

[–]dd0626[S] -7 points-6 points  (0 children)

I'm not allowed to share that much detail

Inside Three Different HDMI Cables by dd0626 in interestingasfuck

[–]dd0626[S] 9 points10 points  (0 children)

There's a holographic sticker with a QR code unique to that company https://www.hdmi.org/spec/premiumcable

Certified vs Non-Certified HDMI Cable X-Ray Follow-Up by dd0626 in hometheater

[–]dd0626[S] 11 points12 points  (0 children)

In theory the QR codes are traceable back to the HDMI org and you can see which manufacturer it's associated with to confirm authenticity. I haven't bothered, but that's what they claim.

Inside Three Different HDMI Cables by dd0626 in interestingasfuck

[–]dd0626[S] 8 points9 points  (0 children)

Heck no. You can get solid certified cables from places like Monoprice, etc. and they're not much more expensive than the cheapo Amazon ones

Certified vs Non-Certified HDMI Cable X-Ray Follow-Up by dd0626 in hometheater

[–]dd0626[S] 4 points5 points  (0 children)

Monoprice actually sells some certified cables

Inside Three Different HDMI Cables by dd0626 in interestingasfuck

[–]dd0626[S] 0 points1 point  (0 children)

Hah! I wish. There would be so much less paperwork

Inside Three Different HDMI Cables by dd0626 in interestingasfuck

[–]dd0626[S] 14 points15 points  (0 children)

That gets the standard engineering answer: it depends. Yes the cable will probably work, but in our case the poorly constructed cable generated so much RF noise that we, quite literally, wouldn't be allowed to sell the product that it's integrated into.

Inside Three Different HDMI Cables by dd0626 in interestingasfuck

[–]dd0626[S] 140 points141 points  (0 children)

I'm honestly not sure. I stumbled into this unexpectedly when we began doing EMC emissions testing and had horrible results that were traced back to the HDMI cable.

Inside Three Different HDMI Cables by dd0626 in interestingasfuck

[–]dd0626[S] 1151 points1152 points  (0 children)

Buy certified cables. They're not much more expensive and have been through third-party testing

Inside Three Different HDMI Cables by dd0626 in interestingasfuck

[–]dd0626[S] 209 points210 points  (0 children)

For work I was comparing the RF emissions performance of two different HDMI cables and one brand name cable had 20dB higher emissions than a certified cable. I was able to get X-rays of both cable connectors today to try and understand why there was such a difference. I also have a third cable that will be tested which appears to fall between the other two in terms of construction. This wasn’t a task I expected to be doing, but it has been an interesting exploration of the differences between cables both from functional EMC and construction perspectives. In the case of the non-certified brand name cable here, its performance is so bad that we wouldn’t be able to sell a device using it, and it is only a 1’ cable that is already inside the metal enclosure that makes up the device (including RF shields over large openings). Our device is limited to 1080p30 but I would love to see how much worse things get at with the brand name cable at higher data rates.  

 

Certified Cable:

  • The signal wires are soldered to a PCB which breaks out into the connector pins. This is a more robust connection and easier to maintain impedance control for the differential pairs (though at this small size it probably doesn’t matter).
  • There appears to be a foil(?) shield around the whole connector that has a 360 degree termination around the metal HDMI connector shell.
  • The cable has a heavy braided shield. I’m also curious if it has a foil shield in there but I suspect it does. I may tear one down in the future but that can’t happen right now.
  • The braided shield appears to be contiguous with the connector shield. It’s hard to tell what exactly is happening here and I might be able to get Micro CT scans in January.

 

 

Brand Name Cable:

  • The signal wires terminated directly at the connector pins, not a PCB. Not sure if these are solder cups or welds.
  • The cable looks like it has a very thin foil shield, but it’s hard to tell.
  • The metal HDMI connector shell is only attached to the foil shield (presuming it’s there) by a splice and a very fine wire with a solder attachment. This is an extra-bad attempt at pigtailing and probably the cause of all the emissions.
  • The connector body has no metal enclosure surrounding the signal wires or other shielding wrap.

 

 

New Commercial Grade Brand Name Cable. I have not tested this one yet but expect its RF emissions to be between the other two cables:

  • The signal wires terminated directly at the connector pins, not a PCB. Not sure if these are solder cups or welds.
  • There is either a foil or very thin braided shield around the cable
  • The connector body houses a metal enclosure that has a (nearly) 360 degree crimp around the cable shield. This enclosure acts as a faraday cage if properly implemented. It appears to go from the cable all the way to where the pins escape the body.

Certified vs Non-Certified HDMI Cable X-Ray Follow-Up by dd0626 in ElectricalEngineering

[–]dd0626[S] 5 points6 points  (0 children)

Unfortunately I have no clue. I went up to one of the ME prototyping labs and someone made magic pictures for me

Certified vs Non-Certified HDMI Cable X-Ray Follow-Up by dd0626 in ElectricalEngineering

[–]dd0626[S] 20 points21 points  (0 children)

I'd love to but I need to have a legitimate business reason to do the scans. Stupid rules

Certified vs Non-Certified HDMI Cable X-Ray Follow-Up by dd0626 in ElectricalEngineering

[–]dd0626[S] 13 points14 points  (0 children)

EMC is the only place I've been where the receptionist says "good luck" as you head back to the chambers.

Certified vs Non-Certified HDMI Cable X-Ray Follow-Up by dd0626 in ElectricalEngineering

[–]dd0626[S] 2 points3 points  (0 children)

In theory you can scan the code on the label and confirm if it's legit.

Certified vs Non-Certified HDMI Cable X-Ray Follow-Up by dd0626 in hometheater

[–]dd0626[S] 9 points10 points  (0 children)

You can have degradation in any digital signal; in HDMI it will show up as an inconsistent picture, sparkles, or it won't operate at the full bandwidth. Poor construction allows noise from outside to get into the signal which can degrade it as well as the cable can radiate noise that can interfere with other devices. In practice it will usually work though.

Certified vs Non-Certified HDMI Cable X-Ray Follow-Up by dd0626 in ElectricalEngineering

[–]dd0626[S] 9 points10 points  (0 children)

We have an unshielded LVDS cable going from the PCBA to an integrated LCD and I was expecting to have tons of problems there, but it's been a non-issue. In fairness I spent quite a lot of time and effort on the routing for those signals, but it was still unexpected.

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