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ACER Predator X34 Owners Club - Page 40

post #391 of 3061
Hosted a LANparty with 9 folks on Saturday, I can call it my X34's last hurrah. I got all 9 gamers opinions of my situation. Their first impression was the monitor is amazing, the size itself gave the immediate response of WOW!

After having 4 of my more seasoned PC building friends game for about 5-10 min each they did notice the scanlines, in both GTA V and Rocket League (both games I spend the most time on too). Framerates on GTA were 85-100 FPS, Rocket League a solid 100FPS. I didn't say anything to them about the issues I have with this it at first, wanted to see if I was exaggerating it. The first two who tested it didn't know what the scanline issue was and just said, the image looks distorted, is there some kind of interference going on? After that the cat was out of the bag, I showed them how it looks with G-Sync off and on,

After this was all done, all 9 people watching the screen, I asked them if I should keep the monitor, 7 out of the 9 said yes.

I then told them the price, 5 out of the 9 said yes.

I then hooked up my $300 Monoprice IPS 1440p monitor side by side with it. They saw how much cleaner the picture was, it's a dramatic difference. One of them actually hooked both up to their PC to see if it was a color profile issue / drivers on my desktop (I had the color profiles loaded from TFT), it looked the same. Another noticeable thing from several of them (including myself) were the colors pop a lot more with my Monoprice monitor, it's much more vibrant. Had another friend reset the monitor to default, fiddle with it for a little bit, I showed him TFT's recommended settings, he tried his own and theirs, no love. Maybe someone can explain to my why this is so, I get it's a different IPS panel but this isn't something like scanlines causing it right? The monitor simply looks bland compared to it, no matter what settings I set it to. I know the Monoprice has a higher gloss AG coat on it, do you think this could be the reason? Some of the monitor review sites for my Monoprice were not very favorable either compared to other IPS screens. TFT even said that the X34 is just about professional grade.

After all this tinkering and testing, I again asked if I should keep the monitor, only 1 out of the 9 said yes. So there you have it, 1 out of 9 gamers would take this defective monitor over a cheap IPS one. I've now spent a day back on my old monitor, I did immediately notice the lack of smoothness in gaming, after all going 100hz G-Sync to 60hz no G-Sync is very noticeable. Dropped the monitor off to UPS this morning to go back to Newegg for a full refund. I'm now wondering if Acer fixes all the issues with this monitor if it's even worth going back to it since I will be losing a good amount of color vibrancy (if the scanlines weren't the cause for it). I may just have to wait for a different monitor with similar specs come to the market with a better panel.
post #392 of 3061
Dear all with scanlines (Part 2): Discussing a possible cause

My first suggestion to users with scanlines even before I had the monitor in hand was to suspect the adapter supplied with the X34 as a cause of the artifact.

Speaking from my experience as an electronics engineer, generally there are a few of rules to follow when working with signals. One such very important rule is to avoid routing your AC power cables near signal lines even if they are twisted pair with shield earthed. AC power tends to inductively and capacitively introduce noise in the signal if it close by. But this doesn't apply to the Acer X34 since the AC power and power electronics are far away in the adapter and only the DC power (19V) line connects to the monitor.

But then, AC power signal can "leak" into the DC side of the adapter and hence enter into the monitor circuitry and result in weird behaviour. This is called Ripple. It is itself an artifact of the conversion from AC to DC. Now, the topic of ripple is long winded and many engineers will know much more about this than I do. But here is a source if you are interested in brushing up your basics in electrical/electronics: Ripple Voltage & ESR

Actual Measurements:
Now that we have the basics out of the way, my initial instinct was to suspect ripple as one possible cause of scanlines among several other possible causes, namely, badly tuned TCON board + row/column drivers, FRC+panel inversion scheme. Long story short, I did find a larger than normal amount of ripple in the Acer X34's power adapter but I don't yet have another good adapter to test with the monitor and see if the scanlines go away. So, while the ripple is high, I still don't have any conclusions: only that the ripple itself is high.

I made measurements using a digital multimeter and a digital oscilloscope (I used two different oscilloscopes to make sure I didn't make a mistake). Here are the measurements:

Average DC Voltage from the X34's adapter.

AC component of the DC Voltage from the X34's adapter.
Frequency of Ripple: 6.667Hz (Time Period: ~150ms). Vpp of Ripple: 300mV (very high).

I compared this with a regular laptop adapter for my toshiba work laptop.

Average DC Voltage of my toshiba laptop adapter.

AC component of the DC Voltage supplied to my laptop by its adapter. (it is very noisy due to high frequency components).
Frequency of Ripple: 500Hz (Time Period: ~2ms). Vpp of Ripple: 16mV.

I can't yet account for the very different frequencies of the ripples in both cases other than to say that they use different technologies or implementations to regulate the voltage. Here is a good source on different power supplies. But I can say that the Vpp ripple of the Acer adapter is high.

I did some digging around and found that there are manufacturers that advertise and sell adapters with 300mVpp ripple. link1 link2 link3 So, it is possible that these are acceptable adapters but my guess is that their Vpp ripple is too high for an application like a monitor.

There are some points I need to clarify:
  • I should have done two things when taking measurements of a power supply with an oscilloscope which I did not: (1) set the correct bandwidth to measure on the oscilloscope and (2) use a capacitor and inductor in parallel as a load circuit. Explained here: Power Tip #6: Accurately Measuring Power Supply Ripple. I didn't do this because item 1 was an oversight and I did not have the L and C available for item 2. Generally, you might find a statement like this in an adapter datasheet: "Ripple and noise are measured at oscilloscope 20MHz bandwidth by a 10uF electrolytic capacitor and a 0.1uF ceramic capacitor in parallel at output connector."
  • The ripple of a power supply will be far less when the actual load is connected. This is explained in the last link with respect to very high frequency ripple so I'm not exactly sure how it applies here. So, it could that this power supply is suitable for the electronics in the Acer X34 by design. If, on the other hand, this ripple issue was overlooked in the design of the X34's electronics, it could very well explain weird behaviour like scanlines. We cannot conclude one way or the other until more testing is done.

Other Points:
  • I haven't visited oscilloscopes and power bricks since my undergraduate days and while I did brush up, I might have made mistakes. Let me know and correct me if you are a fellow engineer.
  • Tomorrow, if I get all the right components, I intend to connect a very clean NI power supply to the monitor and see if the scanlines go away. But if I don't find the components I need (the socket etc.) my testing will be delayed to the weekend. Meanwhile, if you want to test this idea yourself quickly, you could get a spare power adapter with the same or greater current rating as the X34's, with lower advertised peak-to-peak ripple and check if the scanlines go away.

UPDATE: 19th Nov 2015

I just tried a different 19V, 7.1A adapter with thee acer X34 monitor. TLDR: The scanlines are still present. rolleyes.gif My idea that a different adapter might fix things was incorrect. redface.gif

Technical corrections in case someone randomly googles to this post:

I did make a mistake when I recorded the ripple from my toshiba laptop's adapter on the oscilloscope. What I thought was noise in the pics I posted originally was actually the transient response of that adapter's output viewed from a larger time scale. I went back and viewed the same adapter's ripple at a much finer timescale and the transient looks as follows:

The transient goes up to 200mV on the +ve side and upto -100mV on the -ve side.

This is the scale I was looking at it originally from which I could still say that the "average" ripple is only 16mV. But those spikes which I mistook for noise are actually the peaks of the transient response that appear only intermittently on this picture because of the lower sampling time used by the oscilloscope at the larger time scale.

The new adapter I tested was a Liteon Adapter with the same power rating as the Acer X34's.

The Liteon adapter's transient response at full bandwidth: Shoots to +400mV and -400mV.

The Liteon adapter's transient response at 20MHz cutoff.

The Liteon adapter's "average" ripple is 10mVpp.

The only unexplained thing remaining is why the Acer X34's adapter has a slow frequency of 6.66Hz. I am just not at all sure how a power supply can create ripple at frequencies other than 60Hz or multiples of that fundamental. So, I am continuing to use the new Liteon adapter with the monitor because though it has the very high peaks in its ripple, they're is of such short duration that the input caps on the monitor electronics would very easily filter it out. Can't say the same for the 6.66Hz slow ripple from the Acer X34's adapter. (I am still suspicious of it. tongue.gif)
Edited by Mountainlifter - 11/19/15 at 7:21am
post #393 of 3061
Thanks for all the work you're putting into this. Really appreciated.
post #394 of 3061
Impressive, Mountainlifter.

In your opinion, any influence of an UPS wave form output? Square wave vs. sine wave? Could a square wave output create harmonics and increase ripple?

Using a sine wave form output from my UPS, I see no scan lines.
post #395 of 3061
Will be interesting to find out when ACER will actually fix this, I think end of December (if they do fix it) as it is not an "issue" according to ACER
post #396 of 3061
Thread Starter 
Backlight problem is worse than expected. Now it does it at any brightness so its progressively getting worse. I could see it completly failing in 6mo or less. It's definitely not a monitor that will last 2-5 years and not worth 1400 bucks. Asus will be the same.
post #397 of 3061
Originally Posted by funfordcobra View Post

Backlight problem is worse than expected. Now it does it at any brightness so its progressively getting worse. I could see it completly failing in 6mo or less. It's definitely not a monitor that will last 2-5 years and not worth 1400 bucks. Asus will be the same.

That's...disheartening. And you say that the Asus will be the same because it's the same panel, or because of Asus' history? What about the Dell, that also uses the same panel, but without, it seems, the problems that the X34 is littered with?
post #398 of 3061
I don't think the Asus panel will have the same faults. Acer introduced a lot of problems that were never present on the original LG panel. I have had my LG UM95 for more than a year now, with absolutely no issues regarding the backlight.

BLB will still be an issue with the Asus, but the half black screen and scan lines are new problems specific to this Acer.
post #399 of 3061
Originally Posted by DJ Zazz View Post

That's...disheartening. And you say that the Asus will be the same because it's the same panel, or because of Asus' history? What about the Dell, that also uses the same panel, but without, it seems, the problems that the X34 is littered with?


The problems with the X34 are mainly related to the g-sync module and the overclocked refresh rate. Dell has neither and is a "simple" monitor.

post #400 of 3061
Somebody's going to have to interpret for me what Mountainlifter just said? Whoosh.

Also, Mountainlifter, in your post above you wrote: "... because there are people with perfect monitors out there..."

I'm sceptical of that. I really am. I have a feeling that most people saying they have no lines, can't see the lines. Or they simply don't understand the problem.

As we've already discovered, if your frame-rate matches your frequency, then you're not going to see scanlines. You have to know what the lines look like, and you have to know when they appear. I'm not convinced everyone understands this.

However they should if they've read your posts above. Glad to have you here at the forum.
Edited by Mikey- - 11/16/15 at 12:55pm
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