i lately bought a high-end 29inch lg crt with component inputs and what not, model 29fs2rmb.
after a while digging around in it i realised that it has an option to add a vga input with just
a single ic and a few caps and resistors so i gave it a shot.
now - i hooked up my laptop and put on a 640x480 31khz signal and the tv shows it without
any problems at all.
but - hooking up a dreamcast with vga or a xbox360 gives no picture at all. both output
the desired 640x480 31khz and work perfectly on a normal computer monitor.
now - the only real difference between all those signals i have discovered was that my
computer monitor shows both console signals as right on 31,5 khz but the laptop signal
as 31,3 khz.
now my question is - is this actually possible ? afair monitors and tv's don't need a "spot on"
sync signal but the can be in some range between let's say 31,0-32,0 khz. i can assume
the wiring of everything is correct as the picture is very nice connected to a pc.
does anybody have an idea what might be the cause or maybe have a way of testing out
something else ?
cheers
strange sync related problem on vga monitor
Re: strange sync related problem on vga monitor
I doubt that the difference in the khz count is to blame. Possibly a sync polarity issue ? Can you use Powerstrip or a similar program to change the sync polarity on your notebook ? If you lose the picture upon changing the polarity (try all possible: -/-, +/+, -/+, +/-) then this might be the cause.
Re: strange sync related problem on vga monitor
Thanks for the tip - this powerstrip might come in handy a few other times.
Although in this particular situation it is getting kind of ridiculous.
I actually connected another, newer laptop to this tv and it also doesn't work.
I first lowered the the sync to 31,3 then tried all polarities possible, then
tried again with a stable 31,5 again with all polarities and no picture is shown.
Actually saying "no picture shown" is a bit of a lie because with all those non
working signals the screen flickers about every 10-20 seconds showing junk
for a fraction of a second. i can clearly identify my xbox dashboard / laptop
desktop in this but that is all.
Now in this one working laptop i can't use powerstrip. It has an old
SIS M661MX graphics card and doesn't let me into the sync options tab
so i can't check if it will loose the picture changing polarities and stuff....
One thing i just realised is that connecting this working laptop to a normal
computer screen the picture is all yellow. It shows all colours correctly
so the cables aren't swapped but the whole screen is covered in a yellow
tint. Is that
a hint ?
Cheers
Although in this particular situation it is getting kind of ridiculous.
I actually connected another, newer laptop to this tv and it also doesn't work.
I first lowered the the sync to 31,3 then tried all polarities possible, then
tried again with a stable 31,5 again with all polarities and no picture is shown.
Actually saying "no picture shown" is a bit of a lie because with all those non
working signals the screen flickers about every 10-20 seconds showing junk
for a fraction of a second. i can clearly identify my xbox dashboard / laptop
desktop in this but that is all.
Now in this one working laptop i can't use powerstrip. It has an old
SIS M661MX graphics card and doesn't let me into the sync options tab
so i can't check if it will loose the picture changing polarities and stuff....
One thing i just realised is that connecting this working laptop to a normal
computer screen the picture is all yellow. It shows all colours correctly
so the cables aren't swapped but the whole screen is covered in a yellow
tint. Is that
a hint ?
Cheers
Re: strange sync related problem on vga monitor
This is getting even more ridiculous:
I connected my desktop pc to this tv and it shows a clear picture
and also powerstrip allows me to change the settings. The default
setting for polarity is -/-. When change to +/- the screen goes
jibery but still usable, when change to -/+ the screen goes blank
with the occasional pops. But on my non-working laptop it also
has a -/- polarity and all the other settings are identical so there
is no reason for it not to work.
Another thing i discovered which might be related to this problem:
I tried another vga cable and suddenly the working laptop stopped
working. i realised that instead that the difference between those
two is the unused pin in the middle row which is present in the
non-working cable and not present in the working one. After looking
at a few schematics i thought that i'm supposed to ground (in the tv)
all the pins of the middle row and on in the upper row like in this
image - http://image.pinout.net/pinout_sony_eri ... pinout.jpg
I thought that it is supposed to be not used at all so why it's
shortening out the laptop is some mistery. Of course i tried both
cables on the rest of the non working hardware with no effect.
It's obvious that there is some connection between the age of the
hardware that i'm connecting. Although i cannot find any information
about how all those vga outputs might be different.
I'm kind of afraid because i really wanted to buy myself this cheap
ebay cga-vga scaler but i see i have a 50/50 chance of it
working at the moment.
Cheers
I connected my desktop pc to this tv and it shows a clear picture
and also powerstrip allows me to change the settings. The default
setting for polarity is -/-. When change to +/- the screen goes
jibery but still usable, when change to -/+ the screen goes blank
with the occasional pops. But on my non-working laptop it also
has a -/- polarity and all the other settings are identical so there
is no reason for it not to work.
Another thing i discovered which might be related to this problem:
I tried another vga cable and suddenly the working laptop stopped
working. i realised that instead that the difference between those
two is the unused pin in the middle row which is present in the
non-working cable and not present in the working one. After looking
at a few schematics i thought that i'm supposed to ground (in the tv)
all the pins of the middle row and on in the upper row like in this
image - http://image.pinout.net/pinout_sony_eri ... pinout.jpg
I thought that it is supposed to be not used at all so why it's
shortening out the laptop is some mistery. Of course i tried both
cables on the rest of the non working hardware with no effect.
It's obvious that there is some connection between the age of the
hardware that i'm connecting. Although i cannot find any information
about how all those vga outputs might be different.
I'm kind of afraid because i really wanted to buy myself this cheap
ebay cga-vga scaler but i see i have a 50/50 chance of it
working at the moment.
Cheers