Bryan Parkoff wrote:
"Michael J. Mahon" <mjmahon@aol.com> wrote in message 1127029082.502855.95150@g43g2000cwa.googlegroups.com">news:1127029082.502855.95150@g43g2000cwa.googlegroups.com...Knut wrote:The best result was with a CGA 5153 monitor. I had to invert the sync (composite sync applied to hsync in the CGA) but apart from that it is just to match pin to pin on the from the 15pin of the Apple to the 9pin of the CGA. The problem with this CGA is that even if it is a european monitor it does 60Hz and the picture rolls with the 50Hz signal form the Apple.A CGA monitor also requires a vertical sync signal on pin 9. You will need a chip to separate out the vertical sync signal from composite sync and deliver it to the monitor. This chip will require power, which is available on the Apple II side.Michael,Somebody claims that V sync is not necessary, but Knut tried to connect V sync already. The screen still rolls. LM1551 chip to separate H sync and V sync from composite sync already, but the problem exists. We are waiting for the result if US motherboard works with IBM 5153 monitor. V sync may not be needed. We are getting answer very soon.
LM1881...I did some testing on that. This particular monitor (IBM CGA 5153) accepts composite sync on pin 8 (hsync). I used the LM1881 to make a vertical sync but applying this doesn't make any difference. The LM1881 also creates a cleaned composite sync and as well, applying this also doesn't make any difference. It is so that it can almost hold the picture so I think it is the 50Hz 60Hz difference that is the matter.
I actually made a small board with jumpers etc. It has the LM1881, an 74F04 inverter potmeters for making the summing network for analog RGB. I can by jumpers decide the sync signals. The only thing I don't have is a "clean" horizontal sync but I think most monitors ignore the hsync while the vsync pulse is there. I can invert the sync's as I please.
I used it to test some monitors but even though I got several to sync there were problems with line length (Mistsubishi HF2400) or interlacing (old HP VGA). On the VGA monitor the picture was way too brigth too.
Knut