Mini DisplayPort Breakdown

The breakdown

Ah, Mini DisplayPort. The cause of so many of my problems.

I’ve been through broken mDP (Mini DisplayPort) cables, broken mDP ports, and “non-working” mDP to HDMI adaptors causing havoc.

In one case, the entire Surface Book unit was shipped back to Microsoft to be replaced (followed by a reinstall of everything)! Oh, and Dell refused to replace a broken mDP to DP cable after an entire hour on the phone.

However, it’s the problematic mDP to HDMI adaptors that I’m here to post about.

Adaptor #1 ($12)

Mini-DisplayPort-to-DVI-VGA-HDMI-Adapter-for-Macbook-Air-Pro-Surface

This was the first generic mDP to DVI VGA HDMI adaptor I bought off eBay. It broke due to poor construction. Disassembly revealed that the soldering was extremely poor, however my own skills weren’t precise enough to fix it (have you seen how small the mDP connector head is??)

Adaptor #2 ($13)

This is the second one I bought. The DVI/HDMI ports do not work. VGA does work. Disassembly revealed good soldering.

Question marks as to why VGA works but the other two don’t (no signal on sink monitor).

Adaptors #3 and #4 (Cosmol $34.88; $29.88)

I was projecting from my laptop at a venue which had already had two mDP to HDMI adaptors plugged into an iMac.

Comsol Mini DisplayPort to HDMI 4K2K AdaptorComsol Mini DisplayPort to HDMI Female Adaptor 20cm

Each of the two HDMI cables connected to a separate display via the adaptors. However, my laptop would only show output on one monitor and not the other. Why? I don’t know!!

(To be fair, there was a Blackmagic switcher in the mix, but HDMI should work regardless of the source being a Mac or a PC).

At the end of the day, I was undoing all the damage pulled cables at the AV desk, and the screens started working once connected back to the iMac. I really don’t know. Perhaps a button I pushed on some panel on the desk…

The left adaptor is reportedly an active (4K HDMI) adaptor, too. Justifies the RRP.

Update: Turns out that this is actually an incompatibility with the Intel HD Graphics chip on my laptop, and Blackmagic Design Mini Converters (and possible also their switchers). This is why people use Macs for production!!! ?? Windows laptops with NVIDIA chips work ok. My theory is that HD graphics only outputs PC format HDMI, and not “1920×1080 YUV interlaced”. 

The teardown

Out of curiosity and part frustration, I wanted to know why these adaptors weren’t working. So I took them apart.

Adaptor #1 (Square):

  • ANX95833 chip. Could be an onboard VGA controller (qualifies for “active” I suppose)
  • DP126SS chip. Doesn’t do active conversion – not a mention of “HDCP” in the datasheet. (HDMI and DVI are “passive” – passive adaptors still require chips (ref 1))

Adaptor #2 (Rectangle), same deal here:

  • RTD2168 chip. VGA controller?
  • Same DP126SS chip.
  • Why do the HDMI and DVI ports not work on Adaptor #2, if its using the exact same DP126SS chip as in Adaptor #1? No idea.

Did not tear down #3 and #4 – not mine!

Conclusion

This could be more of a lesson on buying cheap stuff off eBay, and not complaining and getting a refund it in time. Or a lesson to buy better built adaptors ($$$). Or maybe the adaptor wasn’t at fault; rather it was a problem with the laptop sending out the HDMI signal. Or a lesson to by a Mac. In short, some things still go unexplained.

Anyways, I’ll be off to buy one of those active mDP to HDMI 4K adaptors for myself.

I wish the mDP connector was better designed – it is so prone to cable breakage and port breakage! Next in turn is my ThinkPad’s mDP port – the inside plastic slot is starting to chip off 🙁 🙁 🙁


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