> ------------------------------ > Message: 8
> Date: Mon, 18 Jan 2016 15:39:38 -0500 > From: "j...@cimmeri.com<mailto:j...@cimmeri.com>" > <j...@cimmeri.com<mailto:j...@cimmeri.com>> > To: General Discussion: On-Topic and Off-Topic Posts > <cctalk@classiccmp.org<mailto:cctalk@classiccmp.org>> > Subject: Re: Preferred way of substituting TFT for CRT Monitor? > Message-ID: > <569d4d8a.4080...@cimmeri.com<mailto:569d4d8a.4080...@cimmeri.com>> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > . . . > You need a monitor (or converter) that supports 25khz. Here's the extent of > my own research: > > 25khz 640x400 SOG monitors > > LCD > - NEC LCD1510+ (not tested) > > - NEC LCD1810 (LA-1831JMW-1) > Mac + PC -- fair performance, poor scaling. > HP 300/98543 -- works, but banded background cannot be completely > faded to black (I got rid of my 1810's for this reason). > > - Viewsonic Vp150 > HP300/98543 -- works well, great background, colors only fair. > > - Viewsonic VP181 > HP 300/98543 -- not perfect but can be adjusted ok. > banded background *can* be faded to black. > > - J. > ------------------------------ ah, this seems to become difficult... Thanks for the data and recommendations. I will have a look at low H-freq. monitors on ebay, maybe I have to revert to an old, heavy and large CRT. I see that many Viewsonic TFT monitors start at 24kHz. I also found http://www.ebay.de/itm/Gonbes-GBS-8200-CGA-15kHz-EGA-25kHz-Arcade-JAMMA-PCB-to-VGA-Video-Konverter-/111506569501 The technical data (http://www.extremehardware.webspace.virginmedia.com/ebay_images/GBS-8200.pdf) says: CGA / EGA - Auto Scan: 14.5 kHz - 16.5 kHz 23.5 kHz - 25.5 kHz <<<< this may fit the HP card? 3 0.5 kHz - 32.5 kHz Martin > ------------------------------ > Message: 9 > Date: Mon, 18 Jan 2016 21:07:27 +0000 > From: tony duell <a...@p850ug1.demon.co.uk<mailto:a...@p850ug1.demon.co.uk>> > To: "General Discussion: On-Topic and Off-Topic Posts" > <cctalk@classiccmp.org<mailto:cctalk@classiccmp.org>> > Subject: RE: Preferred way of substituting TFT for CRT Monitor? > Message-ID: > > <a8192ef71c5c4946a240d25edc8f9448027e4...@exmbx15.thus.cor<mailto:a8192ef71c5c4946a240d25edc8f9448027e4...@exmbx15.thus.corp> > p<mailto:a8192ef71c5c4946a240d25edc8f9448027e4...@exmbx15.thus.corp>> > Content-Type: text/plain; charset="us-ascii" > > > > indeed this machine has a 98204B video board (intended to work with a 35721 > monitor, > > which I don't have). I have not yet found the specs for its composite > > signal. > > It is normal composite video voltage levels with faster-than-normal > horizontal scan rate. > If you have a frequency counter (or something that can be used as one, then > put the 98204B > text board in the topmost position of the 9817, leaving out the graphics board > (the machine ill run without it) and take the top casing off the 9817. Take > care to avoid the > live mains and worse on the PSU board, power it up, and check the HS and VS > pins of the 6845 > (the only 40 pin IC on the board) > > Most, if not all, cheap composite video converters assume US or European TV > rates and are > not going to lock to this thing. If anybody knows of an interface that will > work, > I'd be interested to know about it too (I have a 9817 with the 98204B card, > fortunately > I do have the right montor for it). > > -tony > ------------------------------ Tony, thank you for your explanations. As I understand, the unusual low horizontal frequency is the main problem. I saw that the card has a switch to toggle 50/60Hz vertical frequency (EU/US, original setting was at 60 Hz), but this did not help. I will see whether I can use my oscilloscope to catch the frequencies as I could not find a technical description of the 98204B. ... and I thought today such a simple problem could be easily solved with modern technology... Martin
