24 Dec
2012
24 Dec
'12
1:31 p.m.
On 12/24/2012 12:04 PM, Chris Tofu wrote:
On 12/23/2012 05:29 PM, Chris Tofu wrote:
C: a VGA horizontal scan rate is 31.5 khz. Off the top
of my head I
don't know what a 5151s is, about 22-23 khz allowing for overscan. A
Tandy 2000 or AT & T 6300s is about 25 khz. A vga has 480 lines of
resolution (although there is that 400 line mode, which could
possibly mean vga monitors are dual frequency. Anyone?). 400 is
closer to 348 then 480.
Th 5151 is (IIRC) 50Hz and 18KHz--pretty darned far from the 30KHz
required. Why you can toast your monitor is made obvious if you have a
look at the schematic of the 5151--there's no free-running oscillator in
the the thing generating deflection timing. That is, there's no
synchroguide (anyone remember that term?) type of circuit--the H and V
sync signals pretty much drive the deflection amps with whatever you
deign to put into them. It's quite possible to blow a 5151 FBT by
either screwing up the CRTC programming or hooking the monitor to
something that it was never intended to work with. If you don't
believe me, and you have a system with an MDA/MGA output, I'll be happy
to furnish a program that will render your 5151 permanently dark.
C: I'm sure you're relating your success
w/that monitor accurately,
but is it a multiscanner? I can't even understand how a ttl video
signal is compatible w/a monitor that expects 1 volt peak to peak
rms.
(BTW, the Acer that I'm talking about is a widescreen LCD monitor).
Although full saturation of any color is +1.0V every monitor I tried
won't care if it's +5--nothing bad happens other than getting all
saturated colors. If you're squeamish, you can grab a handful of
resistors and work out a voltage divider--it's not rocket science.
BTW, there's a VGA hookup diagram here:
http://m24.museodelcomputer.org/docs/video_converter.pdf
I imagine that a few components will give the full 16 colors on VGA.
--Chuck