VT1350 won't work with new BenQ XL2420Z

[SUOrange55]

Hello,

I just got a new XL2420Z and can't get VT1350 to work (works fine on my XL2720Z). Every time I enable the custom resolution in NVCP and hit test, my screen goes black. I am using the latest Nvidia drivers (347.09). Any thoughts on what could be causing this?

Many thanks in advance for your help.

[Falkentyne]

Are you using the pixel clock patcher?
http://www.monitortests.com/forum/Threa ... ck-Patcher

Also if you're patching 100hz you should be fine with the default timings (VT1500 will put you at 330.00 MHz exactly) but for 120hz, you may need slightly lower timings.
1920x1080 @ 120:
front porch 48,3
sync width 32,5
HT: 2080
VT: 1350
This will probably need the patcher.

If you don't want to use the patcher, reduce HT to 2040.
Those values will also work for VT 1500, but will put you at 374 MHz pixel clock.

The default values may be a bit too high:
they are, I think, porch 88,4
sync 44,5
HT: 2200
VT: 1350 or 1500 (1500 at these settings puts you at 396 MHz--too high!!!)

[SUOrange55]

Tried all the above with no luck. Lowering the HT and/or using the patcher, I still keep getting a black screen. Same deal with 100hz/VT1500.

[masterotaku]

This sounds like you have the crosstalk/strobe phase setting too high, maybe untouched at 100.

Use the blurbusters utility and put the crosstalk setting to the left. After that, you shouldn't get a black screen when trying a custom resolution.

[Chief Blur Buster]

I just got a new XL2420Z and can't get VT1350 to work (works fine on my XL2720Z). Every time I enable the custom resolution in NVCP and hit test, my screen goes black. I am using the latest Nvidia drivers (347.09). Any thoughts on what could be causing this?

It has happened to me before.

It only occurs when the Crosstalk setting is beyond range that works with VT1350 (outside the range). You need to reset the Crosstalk setting first. Second tip: If you can't adjust Blur Busters Strobe Utility (e.g. adjusting Persistence doesn't adjust screen brightness) then adjust Strobe Phase in the Service Menu all the way down to 0. Service menu instructions are also provided at the bottom of the Strobe Utility page.

Then you should have VT1350 without the screen going black.

[Falkentyne]

Just FYI,
The screen turns black when the persistence reaches "0 ms", or rather, when strobe duty goes down to 000 (even though the actual VALUE doesn't change, the 'value' the duty adjusts (persistence aka "intensity" in the 2430T) does change. As the great masterotaku found out, when the strobe phase gets too high (this ONLY happens when using vertical total tweaks or at the very buggy/nonfunctional 50hz single strobe), the persistence starts going down from its current setting, as if the stobe duty were being lowered, even though it remains at the same value. Once it reaches the lowest persistence value (0.167ms if on a VT tweak), going 1 higher on the phase will shut off the backlight (0 ms persistence). If not using VT Tweaks, the strobe phase will function without the backlight shutting off from 0-100 (except at 50hz).

Strobe phase was only tested by Benq, with default monitor timings and refresh rates. Forcing single strobe for 60 to 75 hz refresh rates was only tested at 60hz, even though --double strobe-- which was forced on in the original v1 firmware, which did not have phase/duty adjustments yet, was tested at 50hz (since the monitor was designed to double strobe at 50-75hz and single strobe at 76-144hz, back in v1 firmware). That's one reason why 50hz single strobe either does nothing, makes the brightness overshoot massively with no strobing activated at all, to compensate for the LED voltage gain (could shorten the lifetime or damage the LED's if you leave it like this), or the monitor will reset itself as if it were power cycled. You can change the persistence and phase, with double strobe enabled (>76 hz), but you have to do it through the service menu due to a strange bug (blur busters windows utility forces single strobe on on any change done, to bypass this bug). The bug is, if double strobe is set ON, enabling blur reduction when blur reduction was disabled, will use DEFAULT (not your custom) persistence and duty settings, but as SOON as the BRIGHTNESS is changed (or when a gamer preset is activated), or phase/duty is changed in the service menu, it instantly switches to your custom settings right away.

Anyway, with the VT 1500 tweak, at 100hz, persistence will reach 0.167ms at phase 059 and shut off the backlighti at phase 060, and at 120hz, persistence will reach 0.167ms at phase 049, and shut off the backlight at phase 050.
Knowing those boundaries, you can easily calculate at what point the persistence will start going down, depending on how high the strobe duty is. For example, at 120hz VT 1500, if your strobe duty were 020, the persistence would start to DECREASE (aka as if the duty were changed to 019) starting at strobe phase 031.

There's really no purpose in using a high strobe duty, anyway; increasing the persistence (strobe duty) moves the top crosstalk band lower, so for best results, you want strobe phase at 000 and the duty as low as possible (assuming VT 1500 tweak, strobe duty 001 moves the top crosstalk settling errors completely *OFF* the top of the screen (although the bottom will degrade a bit; you can read this article from strobemaster who explains that the 'top' crosstalk settling errors are shorter area but more 'intense' while going downwards, its less intense approaching the bottom, but the errors cover a larger area: http://display-corner.epfl.ch/index.php/BenQ_XL2411Z ); lowering contrast from 50 to 0 can give different improved ghosting results depending on the colors and transitions.

If not using a VT tweak, you will want the top and bottom areas balanced to keep the center as good as possible; here, strobe phase 008 and strobe duty 010 give a good balance for 2D desktop, platformers, and most RPG's, but for 3D FPS shooters, where the bottom of the screen has your HUD and the middle and top tend to be far more important, having strobe phase closer to 0 will improve the top of the screen the most, which is the part usually focused on.

[SUOrange55]

Thanks guys.

Lowering persistence to 1.5 (from 3) fixed the issue; crosstalk was already at 0. Tracking in FPS is great thus far with my frames locked at 119 (via Rivatuner), 120hz and VT1350.

Also, Falkentyne, ty for that write up, makes a ton of sense. I'm going to experiment with even lower persistence settings in-game to see what works best.

[Falkentyne]

Make sure you thank masterotaku. He's the one who found this stuff out first.
(I accidentally wrote "think"...big typo, oops)

One very useful thing to remember is that VT tweaks (even up to 1502 maximum; 1503 will always blank the backlight) do NOT change the position of the TOP crosstalk band --whether you use 1125 (default) or 1502 (maximum), the top crosstalk band and all of the phase settling errors will be off the screen (just barely) with 0.167ms persistence (strobe duty 001 if using 60hz pulse widths, while VT tweaks actually (visually) change the distance between the top thick crosstalk band (strobe pulse) and the bottom one, so if you are using a high strobe duty, no amount of phase adjustments will move the top band "up"...it's as high as it goes with strobe phase 000.; all VT tweaks force 60hz pulse widths, so you would use the chart for 60hz based persistence (regardless of your refresh rate) if using VT tweaks!
(http://display-corner.epfl.ch/index.php/BenQ_XL2411Z)

BTW without VT tweaks, the persistence can go as low as 0.07ms at duty 001 at 144 hz! That's VERY dim.......but VERY clear movement at VERY fast speeds!

If you notice, 120hz is rated for 2.5ms persistence maximum, but "60hz backlight pulse widths" (which the monitor switches to when it gets 'strange' timings (e.g. vertical tweaks that go far from the default) mean that it goes up to 5ms (!) That's one reason why VT tweaks at the same persistence as without, make the screen brighter--the persistence is higher. You can also see that at 120hz for example, and at strobe duty 030 (5 ms with VT tweaks, 2.5ms without), you would be at 5ms when 120hz is rated for 2.5ms maximum! (if you run the restart64 driver restarter in the toastyX CRU page (monitortests.com) and experiment, you will see that the brightness WITHOUT VT tweaks, at strobe duty 30, is the same as with VT tweaks at duty 15. So at 030 with VT tweaks, you are running the LED's at twice the ms (they get a voltage current) that they are rated for (5ms vs 2.5ms), so you should never exceed strobe duty 015 when using a VT tweak, at 120hz. At 100hz, don't go farther than 018 strobe duty (WIth VT tweaks). Without VT tweaks, any duty is fine, but you have to deal with the top crosstalk pulse band getting too low....

[masterotaku]

Make sure you thank masterotaku. He's the one who found this stuff out first.

Thank you for that , but you are usually the one that makes the effort to write those long and detailed explanations every time someone has a question. I just bought my XL2411Z and tried to discover all its secrets because of my curiosity and perfectionism. I feel proud of my discoveries every time someone mentions VT1500 or other things I explained. It's like I left a mark in the blur-free community .
However, I usually get tired of writing similar things to different people (we should have more sticky and FAQ threads), and you do the job of helping people perfectly.

Lowering persistence to 1.5 (from 3) fixed the issue; crosstalk was already at 0.

How is that possible? Apart from out of range errors and timing mistakes, whenever I got a black screen it was due to the strobe phase being too high, and touching the blur reduction shortcut to disable blur reduction would make the image appear. Persistence shouldn't matter in this situation .

[Falkentyne]

I'm guessing that he had strobe phase at 100 but as soon as he ran the blur busters utility, it instantly reset it to a lower value?