5 Nov
2007
5 Nov
'07
11:31 p.m.
Pete Turnbull wrote:
On 05/11/2007 12:49, Jules Richardson wrote:
Heh - oops :-) I'm thinking that taking monitors overseas with me isn't much
of a long-term solution though; they'll fail eventually and patching them up
US-side is less than ideal.
Having a gadget available that's either readily obtainable within the US or
easily buildable seems like a better long-term solution; it's just a question
of whether the slight (typical) frequency differences / screen geometries
between the two markets are going to cause a problem in finding something that
works off the shelf.
No, I don't need a PC. I just need
*something* in the US that can cope
with typical UK-style picture formats (typically 'home' micros in the
UK will be designed around PAL signals at 625 lines interlaced I
expect, whereas I expect US micros of the 80s were geared more toward
NTSC displays of 525 lines)
I'm not sure if VGA will cope either - I don't think a typical VGA
monitor will sync down to the frequencies involved (i.e. converting
TTL to the necessary 'analogue' RGB of VGA is the easy bit :-)
It's a pity you didn't ask this yesterday when you were here: I could
have shown you my workshop monitor. Alexis' idea about the circuit should work too.
His surmise about 1V
pk-pk for VGA is correct
I didn't think many VGA displays would sync down to the frequencies used by
the older kit, though?
I've used a similar circuit to do exactly
that, and something not too distant to combine all the signals to make
composite video (I could have shown you the ISA card for that too,
though it only uses the ISA bus to get power). If you need to merge
hsync and vsync, a simple XOR gate (1/4 of an LS86, for example) will do
well, but often you can get away with just combining them, wire-or
style, possibly with a couple of small-signal diodes.
Yep, I've done the LS86 'trick' before for combining syncs - but lots of the
old kit I have outputs composite sync, and for driving something like VGA I
expect I'll need separate syncs. Of course I suspect I can tap into them
somewhere within the circuitry of whatever system's hooked up to the display
(ISTR that splitting a composite sync signal is a bit complicated, but it's
been a while)
Have you tried any flat-screen monitors? Some of them
are designed to
work as TV displays, and will handle horizontal rates in the 15kHz range
as well as signals in the VGA (etc) ranges.
Hmm, I've not tried that. The 19" Hercules LCD I have might work I suppose
(and it's so awful for normal work that it's getting dumped for a good
old-fashioned CRT soon as I get my stuff across the pond anyway)
cheers
Jules