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Author Topic: Hantarex CT EQ/3 28" issue - vertical sync change?  (Read 1058 times)

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Hantarex CT EQ/3 28" issue - vertical sync change?
« on: March 27, 2018, 03:58:02 pm »
Hello all!   ;D

New to the forum after recently purchasing a Hantarex CT EQ/3 28" monitor - spec here

However, already experiencing a couple of issues which I'm not sure whether its me being an idiot or whether anyone has had any experience with the same issue. The monitors only video input is VGA. The spec says that its capable of up to 120Hz vertical sync - but I cant get it above 60Hz. Im using it for a Panasonic 3D0 console and a Megadrive (first of the collection!). Whilst these are mostly fine with 60Hz rate, I also use the monitor to plug my laptop into, which is difficult to look at for any long periods at 60Hz as the flicker gets my eyes!

Have tried changing all options on the manual menu but it doesnt actually let me access the V sync rate here, only mocks me with what it is (i.e. displays 60)! On the back of the monitor there is three little circles, the center one has a dial for vertical amplitude but the vertical sync and shift dont have any dials (nor evidence that there should be any!) only small holes. Have attached a pic for reference.

Does anyone know how I am to increase the vertical sync rate?? Also having an issue of some slight double vision on some lines, but presumed this would be rectified through the vertical shift? (also cant access!).

If anyones able to help, I would be really grateful - from a newbie to the field!

« Last Edit: March 27, 2018, 04:01:29 pm by MARMS »


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Re: Hantarex CT EQ/3 28" issue - vertical sync change?
« Reply #1 on: March 27, 2018, 08:42:48 pm »
Hmmmm, there's a lot to unpack in the details you've provided.

The spec sheet you provided says the monitor has a horizontal scan frequency of 31-38kHz. This means it takes a VGA signal (640x480 resolution) through the HD15 plug commonly called a VGA plug. A VGA signal is 31kHz. This is the lowest resolution your PC or laptop will output by default. You can go lower than this using an S-video port of some type (bad idea) or special drivers depending on hardware.

CRT’s scan left to right, one line after the next down the screen. They don’t care so much about the number of pixels in each line (horizontal resolution). They do, however, care very strongly about the number of lines (vertical resolution) they can display per second. This is the horizontal scan rate. So…

525 lines x 60 fps = 31kHz.

(525 is 480 visible lines plus a blanking interval of 45 lines).

The V-sync knob on the set is V-hold, and is to stop the picture rolling. On newer monitors that function is normally automatic. If you want to up the framerate, you do so by modifying the signal going *to* the set, not with an adjustment *on* the set. And even if you do change the framerate on your PC, you’re going to run into trouble fairly quickly if you try to increase vertical frequency (fps) at that resolution as you’ll hit 38kHz at about 72 fps. And higher resolutions are going to have trouble right away, as 800x600 will only fit at ~56fps, so you’ll have to make a custom resolution somehow. The horizontal scan rate is usually the limiting factor, the other numbers you can normally play with a bit.

TBH at 60p (60Hz/fps) you shouldn’t be seeing flicker. That tends to be more of a problem with interlaced resolutions. Though with the cited specs I'd guess this monitor was intended for early PC presentation use in the mid to late 80's, so maybe it flickers. You might even find that a 400@70p resolution or something from old DOS versions like that looks a lot cleaner vertically, i've seen similar effects from older presentation monitors designed for PAL 576i - they take 480i NTSC but don't look nearly as nice even using RGB. Remember that 15kHz and even 31kHz games look best at native vertical resolution, for example putting a 240p game on a 256 line video mode can make it look pretty bad. You don't want to mess with the vertical resolution if you can possibly avoid it. For video content, going below 480 lines really starts losing detail.

Next, I have no knowledge of the CDO, but I imagine it’s like the megadrive in that it only outputs 15kHz video. Probably 240p, but possibly 480i at a pinch. Most older consoles up to the PS1 only output 15kHz video. This is going to be a problem if the set only syncs to minimum 31kHz (480p, as above) as listed. You will need something like a linedoubler, but to begin with i have no idea what video connection you’re planning to use.

I'll admit i'm not 100% on what you're saying you've got working. If you have more info about what you’ve already done regarding testing, and what you plan to do, we might be able to help further. If the specs you provided are correct, it really looks like this set was designed to take from 640x480p up to only 640x576p, nothing else. And even then that last resolution is over the bandwidth limit...
« Last Edit: March 27, 2018, 11:27:18 pm by buttersoft »


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Re: Hantarex CT EQ/3 28" issue - vertical sync change?
« Reply #2 on: April 02, 2018, 02:12:36 am »
Hi Buttersoft,

Thanks for the detailed reply! - really appreciated.

I did alot of playing around on your advice and you're very correct, it actually works best at 60Hz I think I will have to just deal with the slight flicker it has.

Converse to this, I had a play at work (work in a vision science laboratory) where we have a 'pattern stimulus generator' which I can control the output of much easier (i.e. whats being output the VGA, has to be a checkerboard pattern however). To my surprise when first plugged (see below pic) in it was outputting 100fps vertical freq with 62.5k horizontal?!

Thats not even in the spec... whilst the flicker definitely disappeared, is there any explanation for this do you think? Going to have another play around this week with the settings on my PSG but certainly much better than I first thought! Will then try to modify the output from my laptop...  :badmood:

Thanks again for your help!


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Re: Hantarex CT EQ/3 28" issue - vertical sync change?
« Reply #3 on: May 10, 2018, 06:18:50 am »
Hi all,

Following my false sense of success, my screen seems to display a double screen whenever I input a signal... (see last post for pic).

My card lets me specify the exact outputs for the VGA which are going into the screen, do any of you know how I might improve this to make it only 1 screen? Ideally want to keep the frame rate above 60Hz... (70+ if possible!). Spec of the monitor is in last post.

Its asking for...
Width (pixels) :currently 800 but tried at 640 with no difference
H-Sync width (1-64): 6
H-back porch (1-256): 101
H-front porch (1-2048): 111
Invert H sync? No
Height (pixels): currently 600 but tried at 480 with no difference
V-Sync width (1-64): 32
V-back porch (0-255): 12
V-front porch (0-255): 12
V to H delay (1-16): 5
Invert V-sync? No
Aspect ratio: 1.33
Frame delay time (ms): 14.5
Frame on time (%) 91.7

DMA Burst length (1-128): 64
Pixel clock divider=1
Pixel clock frequency 12000
Pixel clock multiplier=1
Pixel clock: 48Mhz

Must admit I'm way out of my depth here - any advice or guidance anyone has to what settings I could change to potentially make this better would be much appreciated!!

Many thanks