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Discussion Starter · #1 ·
I was wondering if anybody knew whether the DTV-200 generates positive or negative sync? My suspicion is that it is positive. Anyone know if the card can generate negative sync if so how do you configure for it? Doesn't appear to be a whole lot in the registry by default.

TIA,

Tom
 

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In RGB mode the H&V sync are negative per VGA specifications. In YpBpR they should be trilevel though I never looked at it with a scope I can if you need to know.


One potential problem is the levels. VGA is TTL or 0 (actually up to 0.7v) to 5v (but can be as low as 3.8v). It is typically ment to see a 1K ohm impedance though some designs can drive full level into 50 ohms or even lower. If you are feeding a projector with a 75ohm impedance for H&V it could be loading down the HiPix. The early Dish 6000s had this problem.


Another though rare problem is DC level. The Hipix uses 5V as the baseline and 0v as the pulse. If the projector expects to see a true negative voltage fro the sync pulses, it would never detect them from the Hipix since they don't go below the ground reference. Again this is very unlikely though possible on some equipment.


What problem are you having? Can you give us more deatil?
 

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Quote:
In RGB mode the H&V sync are negative per VGA specifications. In YpBpR they should be trilevel though I never looked at it with a scope I can if you need to know.
Glimmie -


I'd personally be very interested. Most component analog sets don't really seem to need the tri-level sync but I've wondered about this and posted a few times. Those of us using HTPC's with AA 9A60 transcoders for instance are not sending tri-level sync to our sets. I don't think the DTC-100 does either.


My Toshiba TN55X81 seems to accept this just fine but I've always wondered if it would be happier with the correct tri-level sync signal.


- Tom


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Discussion Starter · #4 ·
Glimmie,

To answer your question the problem I am having is that I can only sync up my Barco Graphics 800 projector at 720 x 480p. The BG 800 requires negative sync not sure exactly if that it is a negative voltage or not as I don't have the service manual or any real technical specs. I know that folks that desire to connect the DTC-100 to their Barcos need to invert the sync there are a number of circuits or interfaces like extron units that have switchable sync. I also use powerstrip to set negative sync for my ATI graphics adapter. I don't have a display during bootup until powerstrip loads and changes the adapter settings which appear to default to positive sync. I have the HiPix setup in RGB.

Regards,

Tom


[This message has been edited by Tom Patrick (edited 09-04-2001).]
 

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For some VGA resolutions, the syncs are positive, and for others, they are negative, and you have to check the specific resolution to be sure. PowerStrip makes this a moot point. I know that my Hipix card, when displaying 1080i provides negative sync, and I've seen no way to control or change this. Some displays, like Panasonics, don't seem to like the VGA syncs that the Hipix provides. This could be due to my transcoder though, KeyData. I did try the RCA transcoder too, and I couldn't get 1080i to work at all.
 
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