hack a PC VGA monitor for 15KHz?
 

I've been thinking, how hard would it be to modify standard 31Khz VGA CRT monitor so that it can display 15KHz picture? (turn it into multisync)
I'm hoping it might be easier than building scandoubler..

Cheaper to buy a 15KHz capable monitor or a TV.

Only an TV / monitor engineer would be able to provide information about how monitor chassis work and how complex it would be to change. I imagine it is not practical. But you never know.

you can purchase for example a Kworld TV box wich have tons of inputs,RGB SVHS,composite,SCART ...and will output to VGA

if there are room inside your monitor you can put the TV box there and you get a full 15hz monitor :D

.. with jerky scrollers? :-)

Can you link us to the model you meant?

theres also enouch juice going round a monitor to kill you if you don't know what you are doing.

LCD PC monitor can be "quite" easily tweaked for 15kHz... CRT is a bit different thing - impedance for all inductance's will be to low, so You need to add variable voltage power supply for whole H circuit, change components (RC) - it can be made but... IMO not worth to bother.
LCD monitors are easier to tweak - only need some uC with usually I2C port and modify some values for AFE and ADC (syncing. levels, sampling, clock recovery) - if You find datasheet for AFE it should be "quite easy"

Hmm... tell me more... :evilgrin

this model for example

http://www.kworld-global.com/main/pr...id=6&prodid=26

you can connect anything there PSX,nintendo,AMiga,Nintendo 64...and will output to VGA at the resolution you want
and there are no jerky scroll if you monitor can do 100hz and 120hz at high resolutions
for example a big aperture grille CRT monitor NEC or Sony 19 or 21 will make the best job

Bummer.

Spec says it doesn't have an RGB input. The only "native" Amiga input is composhite. So quality will suck but... only £40....

check at the connection diagram

it have VGA input also....must works using the common silver VGA adapter made by commodore
also it have SVHS input and you can get that better signal from the cxa1145 chip or using an adapter like the amigamaniac

VGA input is pass through only. Just a switch. Useless for native 15KHz Amiga video.

OK so you could use this with the silver sync dongle in double scan modes but they are really workbench only, i.e. not games.

As you said this input could be used for an RTG gfx card to switch between RTG and Amiga native.

Ok, yes if you added SVHS output to your Amiga you'd get a slightly better picture when using one of these but it is not what I'd consider a native Amiga output. Good point though.

maybe is a pass through....maybe not
don't forget that the KWORLD device is really a scan doubler and maybe works with native 15hz signals through VGA input
and don't forget that most LCD TV can display Amiga native signals using the silver adapter so...this is a similar device..must works

If it is like any of the others I've tried, it is a gen-locked analog RGB pass through with OSD overlay. (So they can display the menu when displaying the VGA input).

I've experienced others that don't. If it does, I wonder why they are not pushing it as a selling point. Or why there are no threads on the internet about it, you'd think someone would have discovered it?

Some do, most don't. (At least the ones tried by Amiga users here, on Amiga.org and Atari users over at Atari-forum.com) But if you live in Europe, all take 15KHz RGB through their SCART input. (Although not all like non-interlaced screens)

To me, that is not logical reasoning (and not true either). To me.

this is a new device......that's why there are not threads yet on internet
Kworld generally is not interested in the Amiga market...they develop that devices for the PSX,nintendo genesis and other consoles
you can check that the model comes with dedicated cable for the PSX
so..the selling point you are talking about is rare

btw, there are others TV BOX models with RGB input and VGA OUT ...specially dedicated to gamers who want the maximum quality on their PSX or nintendo or genesis
I put that model as simple example for orange

So you have tried it yourself and it scandoubles a 15kHz picture fed into the VGA port?

Yup, a composite video cable.

Yes, I've seen them. XRGB etc. but they are a lot more than the $59 RRP of the KWORLD device. Perhaps you're right... hope someone tries it soon.

Nop sorry I have not tried...but should work using the silver adapter...aa I said to Alex ...that Kworld Device is an LCD TV without the screen

If You look at the typical AFE (Analog Front End) for video monitors:

http://www.analog.com/en/audiovideo-...s/product.html

(this one is modern due of HDMI with HDCP support but there is lot of older IMO even easier to use - more available documentation)

, there is lot of registers in such AFE (usually AFE is together with ADC) - there is part related to the clock recovery (ADC trying to sample video signal with exactly same frequency as video is produced in source), sync extraction (most of AFE is equipped with some auto sync detection - You only need to specify group of video standards for search - ie H and V sync range). main problem for monitors is that they support on VGA only typical and common modes for PC world even if hardware is fully capable to acquire whole range of lower standards. Monitor manufactures simply don't use this functionality - limitation is related to software (firmware) for monitor not hardware of monitor - this can be easily seen for LCD monitors that are equipped with SCART connector - they use exactly same electronics as VGA but if You switch to SCART they simply run register settings for AFE that allow to sync and recover clock from TV video standard.

So whole tweaking for LCD which not support anything bellow 30kHz is to switch (ie reprogram) registers in AFE in that way that this support 15kHz, second , this must be done in that way that allow next part of monitor to rescale sampled data to native LCD size.

best is modify original firmware for monitor that whole monitor began work with everything bellow 30kHz - still it can be made due of this that lot of monitors have firmware in some kind of flash and can be reprogrammed.


So idea is simple but... real life can be more complicated but IMO is better to do software modification in LCD than redesign H circuitry in CRT.

Looks like that box has no RGB input, as I thought. Shame.

Ok, I already knew this, but I thought you would have more precise information on how to achieve It.
There are a lot of AFE from a lot of manufacturers, and some of them require a NDA for getting some useful information, so It's impractical.
But I agree, in theory It's more easy than electronics redesign, if you have the right information.