Testing a Video Signal
in [Design]
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From: Jan Panteltje on 18 Jan 2010 06:41 On a sunny day (Mon, 18 Jan 2010 02:14:05 +0000 (UTC)) it happened "Mike Warren" <miwa-not-this-bit(a)or-this-csas.net.au> wrote in <xn0gpaenva4zfj001(a)news.aioe.org>: >www.mike-warren.net/tmp/DSO1-ECS-web.jpg start: The burst is way too small, possible teh color killer activates. >What tests can I do to try and work out what is wrong with >the signal? Feed it trough an amp that peaks above say 2 MHz, to icrease chroma amplitude, to see if the collor killers de-activate. >The supplier claims there is nothing wrong with their cards >as no one else has ever complained. goto start
From: Jan Panteltje on 18 Jan 2010 06:42 On a sunny day (Mon, 18 Jan 2010 03:01:53 +0000 (UTC)) it happened "Mike Warren" <miwa-not-this-bit(a)or-this-csas.net.au> wrote in <xn0gpafxxbugxq004(a)news.aioe.org>: >Michael A. Terrell wrote: > >> >>Mike Warren wrote: >>> >>>We have just purchased a quantity of PCIe video cards with >>>TV out (S-Video) and can only get a monochrome picture >>>from the S-Video output. >> >> >> S-video has seperate Luminance & Chroma channels. You need both to >>get a color image. If you are feeding a composite monitor, you need a >>S-video to composite adapter. > >Thanks for the reply. As I explained, I'm converting through >a 1000pF capacitor. This have been sufficient for me for over 6 >years, and anyway I have the same problem feeding into a >S-Video input to the monitor. The color burst amplitude should be the same size as the syn pulse. (About 300mV). Your S-Video interface sucks.
From: Mike Warren on 18 Jan 2010 08:36 Phil Allison wrote: >"Mike Warren" >> >>-These cards produce a B&W picture on 3 separate monitors >>(2 LCD and one CRT) All monitors work fine with the other >>brand. The 15 year old CRT monitor will produce a colour >>picture from this card for a few seconds when cold. > > >** The symptoms fit with a colour sub carrier frequency that is too far >off for your monitors to lock onto. That's what I was guessing, but hoped there would be an easy way to confirm. >The allowed error ( for a broadcast signal ) is only 5 Hz in 4.4MHz or >about 1ppm - which is way better than an un-trimmed crystal can provide. > >Being only a 10 cycle burst means measuring it directly is not possible. > >If the PCI card uses the computer's clock frequency for all timing, then >you are stuck. > >If there is an on board 4.43MHz crystal - maybe you can tweak it a bit. There is only one crystal. I'm guessing it's the master clock and all the other clocks are PLLs. I don't fancy getting involved in hardware mods to 100 video cards so I'm hoping there is a software trim available. I've asked the manufacturer and are awaiting their reply. Thanks for your reply, Phil. -- - Mike
From: Mike Warren on 18 Jan 2010 08:39 Jan Panteltje wrote: >On a sunny day (Mon, 18 Jan 2010 02:14:05 +0000 (UTC)) it happened "Mike >Warren" <miwa-not-this-bit(a)or-this-csas.net.au> wrote in ><xn0gpaenva4zfj001(a)news.aioe.org>: > > > >>www.mike-warren.net/tmp/DSO1-ECS-web.jpg > >start: >The burst is way too small, possible teh color killer activates. I don't believe this is the case here since the good card has exactly the same signal level. Also, I've had others with even lower colour burst still work fine on my test monitors. Thanks for your reply. -- - Mike
From: Mike Warren on 18 Jan 2010 08:42
Jan Panteltje wrote: >Your S-Video interface sucks. It certainly does, but the same type of circuit is very commonly used, and I've used it myself in hundreds of these machines since 2003 without a single complaint of no colour. -- - Mike |