Weird behavior with a PM161Q

hbquikcomjamesl
hbquikcomjamesl Member Posts: 4 New User
in Monitors
I recently purchased a PM161Q; it is now the primary (and only) screen on my new Linux box (a System76 Meerkat).

Everything works beautifully. With the USB-C cable that came with the monitor.

Except that with the USB-C socket coming out the side of the monitor, a rather stiff cable with a straight plug isn't exactly ideal for a non-portable installation.

So I bought a right-angle USB-C cable. It works, but it has problems.

With the original cable, the screen is rock-steady. When the Meerkat blanks the screen, after standing idle for a while, it blanks; when I do something to restore the screen, it comes back, at full resolution.

But with the cable I bought, after about 20 minutes idle, the screen abruptly jumps to a much lower resolution, and stays at that resolution until the system is rebooted.

I can't make head or tail of why it would do that. Can anybody shed any light on the problem? And/or recommend a right-angle USB-C monitor cable that would work better?

Best Answer

  • hbquikcomjamesl
    hbquikcomjamesl Member Posts: 4 New User
    Answer ✓
    It was determined that the primary (and most serious) symptom, the apparent resolution change, was in fact a magnification change: the display driver was spontaneously switching from 100% magnification to 200% magnification, and it was also occurring with the factory cable. With this information, System76 technical support recommended disabling the HiDPI daemon in the display settings; this solved the problem.

    The other symptoms were most likely from the cable I was using, as they did not occur with the factory cable. I then bought a different right-angle USB-C cable, one that was not e-tagged. It arrived late yesterday. I tested it this morning, and everything works perfectly. 

    While I'm satisfied with my PM161Q, it could be improved. Personally, I recommend that on the next version of this product, (1) there ought to be built-in 75mm VESA mounting holes, for non-portable applications (I had to fabricate and attach a bracket in order to mount it on a support arm), and (2) place the USB-C and Micro-B connectors a bit further from the edge, so that there isn't an exposed plug sticking out of the side.

Answers

  • billsey
    billsey ACE Posts: 34,219 Trailblazer
    It's likely not in the right angle connector, but instead in the cable quality itself. Try one that's got a bit more heft to it, it will likely have better shielding.
    Click on "Like" if you find my answer useful or click on "Yes" if it answers your question.
  • hbquikcomjamesl
    hbquikcomjamesl Member Posts: 4 New User
    Thanks.

    Shielding could be it. The original cable is quite heavy and stiff, much more so than the one I bought.

    Or (based on an answer I got from System76 tech. support) it could be that the cable I bought was e-marked (an attribute that was completely meaningless to me until late yesterday afternoon), and the e-marker chip was somehow getting into an argument with either the monitor, the Meerkat, or both.

    Or both inadequate shielding and the e-marker chip could be involved.
  • Bertsboy
    Bertsboy Member Posts: 4 New User
    sorry for gatecrashing, I'm a newbie, not sure how to start a new post, and wanted to ask a question about this Acer portable monitor.

    I thought the size and the look of this monitor were cute, so bought one from a high street chain.

    I wanted to connect it to my old windows 8.1 desktop tower (which works perfectly). Have tried 3 leads without success - from the monitor a usbc, one with hdmi attached to the tower, one with vga attached to the tower, and one with usb-a attached to the tower.

    As there was no light on the monitor, I tried in each case, turning the monitor on and off, on and off & on, and while I can see the lights/power on my tower, keyboard and mouse are all on, absolutely nothing at all on the monitor. No light, no sound, nothing at all.

    In desperation the shop have kindly accepted to take this monitor back and replace it with another 15.6" Acer 161q portable monitor.

    but I have to know, are they compatible? Is there a known issue where this monitor will not work with my tower windows 8.1 pc using one of the 3 usbc connections? Have we been doing something wrong? What connections should work?

    many thanks for your advice, the new one is due in a few days time and if its not compatible best to know now..

    cheers everyone
  • billsey
    billsey ACE Posts: 34,219 Trailblazer
    @Bertsboy you use the "Ask a Question" button to start a new post. Repeat your message in a new thread so it doesn't get confused with this one... Likely your PC is too old to support DP over USB-C, so won't work with this monitor.
    Click on "Like" if you find my answer useful or click on "Yes" if it answers your question.
  • Bertsboy
    Bertsboy Member Posts: 4 New User
    ta, I have now got this in a new posting, pls refer to the new posting peeps, ta!!! Esp about the being too old bit too
  • hbquikcomjamesl
    hbquikcomjamesl Member Posts: 4 New User
    Answer ✓
    It was determined that the primary (and most serious) symptom, the apparent resolution change, was in fact a magnification change: the display driver was spontaneously switching from 100% magnification to 200% magnification, and it was also occurring with the factory cable. With this information, System76 technical support recommended disabling the HiDPI daemon in the display settings; this solved the problem.

    The other symptoms were most likely from the cable I was using, as they did not occur with the factory cable. I then bought a different right-angle USB-C cable, one that was not e-tagged. It arrived late yesterday. I tested it this morning, and everything works perfectly. 

    While I'm satisfied with my PM161Q, it could be improved. Personally, I recommend that on the next version of this product, (1) there ought to be built-in 75mm VESA mounting holes, for non-portable applications (I had to fabricate and attach a bracket in order to mount it on a support arm), and (2) place the USB-C and Micro-B connectors a bit further from the edge, so that there isn't an exposed plug sticking out of the side.

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