C-sync to H + V sync
Rafe Aldridge
Hello all,
I've a TV tuner intended for use with an RGB monitor +
Composite Sync.
However, my monitor is a PC Multisync monitor and requires
RGB + H sync + V sync.
So how do I get from C sync to seperate sync signals?
Also someone suggested that I may damage my monitor by using
it by using this tuner. Any truth in this?
Thanks in advance for your help.
Rafe
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Rafe Aldridge - r...@sirius.tn.rl.ac.uk
R65, Rutherford Appleton Lab, wwWWww
Chilton, Oxon, OX11 OQX, UK. o o
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Mike.Ellis
: Hello all,
: I've a TV tuner intended for use with an RGB monitor +
: Composite Sync.
: However, my monitor is a PC Multisync monitor and requires
: RGB + H sync + V sync.
: So how do I get from C sync to seperate sync signals?
The simple way to do this is to use two capacitors and two resistors.
Use one of the C's and one of the R's to form a low-pass filter
between C-sync and ground feeding the V-sync input of the monitor -
the 3db point of the filter should be somewhere between 100Hz and
10kHz, so there's plenty of scope for using bits from the bin.
The second C and R should be used to form a high-pass filter between
C-sync and H-sync. The 3dB point of this filter should also be
somewhere between 100Hz and 10kHz, so once again scrap parts are
easily used: when I did this I literally put my hand in a bin of C's
and the other hand in a bin of R's, pulled out two of each and build
the circuit.
Of course, if you want to be really flash you could build a full
sync-sep circuit - I suppose you could do it using an LM1881, but
that's really overkill for this job: after all, the LM1881 is only a
couple of filters in an 8-pin package with a few monostables built in
to provide the flash functions like even/odd field separation and so
on.
Have fun!
Cheers,
--
Mike Ellis, mi...@dd.eng.bbc.co.uk
BBC Research and Development Department, Avenue House, Chiswick, London, UK
-- Any opinions expressed are my own and may not reflect those of the BBC --
David Grieve
: Hello all,
: I've a TV tuner intended for use with an RGB monitor +
: Composite Sync.
: However, my monitor is a PC Multisync monitor and requires
: RGB + H sync + V sync.
: So how do I get from C sync to seperate sync signals?
Use an LM1881 video sync separator.
: Also someone suggested that I may damage my monitor by using
: it by using this tuner. Any truth in this?
Possibly. TV has a field rate of 50Hz and a line rate of 15.625kHz
whereas VGA has a field rate of 60Hz and a line rate of 31.5kHz.
The frame rate is close enough - it may not work, but it won't do
damage - BUT the line rate is clearly way off. In a fixed sync
monitor, feeding the wrong frequency line rate can do damage because
the line scan is essentially a tuned circuit and bashing it at the
wrong rate can cause spuriously large voltages which cook the output
transistors. However, you said you had a multisync - in this case
it depends what rates it covers. Early multisyncs and dual-syncs
tended to cover 15kHz'ish and 31kHz'ish (and this would be OK for
your purpose), newer multisyncs have stopped supporting the lower
frequencies in favour of adding higher ones like 40...50..60kHz
which are required for resolutions in the 1024+ range. It depends
on the model AND the vintage of the model e.g. original NEC 3D
did 15kHz, newer NEC 3D don't.
David.
syc...@g386bsd.first.gmd.de
>I've a TV tuner intended for use with an RGB monitor +
>Composite Sync.
>However, my monitor is a PC Multisync monitor and requires
>RGB + H sync + V sync.
The easiest way i can think of is: use a LM 1881
available through National Semiconductor for example.
It's pinout is like this:
+----+ 680kOhm
Comp. Sync out 0.1uF 1<| |>8 5-12 Vcc +-[]-+
Comp. Video in --||--- 2<| |>7 Odd/Even output | |
Vert. Sync out 3<| |>6 ----------------+-||-+---Gnd
GND 4<| |>5 Bururst output 0.1uF
+----+
Connect your Comp Sync to the Comp Video input and you'll get the HSync at a
range of your Vcc on pin 3. Pin 1 provides you with the comp. sync , which you simply
use as HSync. The chip shouldn't cost you more than about $4 (9 DM in germany)
>Also someone suggested that I may damage my monitor by using
>it by using this tuner. Any truth in this?
Hmm ... Depends on the freqs your monitor can handle.
I myself run a NEC II and a Targa Multisync on my Amiga (same freqs
as PAL standart , 50 Hz V-Sync, 15 kHz HSync ) since 2 years without
any problems. I doubt that nothing more will happen, except your monitor
might loose sync from time to time.
Have fun , Ralf
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