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Old October 23rd, 2007, 07:25 PM   #1
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xenarc doubling

Hi, I noticed someone had a similar problem with a different monitor (Steven Fokkinga?), but I never heard the resolution. I'm having issues with image doubling using the VGA input on my Xenarc 700 yv. This is my setup: HVX200 (component out) -- Mayflash VGA box -- Xenarc.

I think I'm having issues getting it to correctly detect the resolution coming off my VGA box. The issue is driving me crazy. The VGA box is a Mayflash YPbPr to RGBHV VGA box, and it always worked before with my previous Xenarc monitor. Do I have a defective scaler in my new LCD?

The Mayflash works: I previously had a Xenarc 700tsv which worked perfectly with this very same Mayflash unit, and the Mayflash still works fine sending a signal to my desktop monitor. (I "upgraded" to the 2007 700yv because I trashed my 700tsv while trying to pull the touch-screen out.) Has any one else seen this? Are there other brands of YPbPr to VGA boxes which I might try?

Any info or tips would be helpful.
-Jack
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Old November 9th, 2007, 03:42 PM   #2
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Saw this..and err.. bought it.. just now...should be great for using my lilliput(which doesnt work with my mayflash). downscales hd to any res u like..sounds too good to be true really(it has some mixed reviews but bad reviews seem to be from people unlrelated to video)..i should be able to run it from an old 12v battery pack ive got and monitor my hd signal at 800x600(not exactly hd but hopefully good enough to focus).

i will post results...hope it helps


"StarTech.com (VGA2TV2WAY) Video Capture
Information: Product details
Price Range: $166.00 - $206.00 at 7 stores
Manufacturer: StarTech.com - See Site

Convert between resolutions and video formats with StarTech.com's VGA2TV2WAY, a two-way VGA to HDTV, HDTV to VGA scaler. Combining the features of a video scaler, a scan converter and a format transformer, the VGA2TV2WAY automatically detects your source's input resolution and allows you to customize its output..."
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Old November 9th, 2007, 08:25 PM   #3
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Thanks Craig, that's huge.

I'm extremely disappointed with Xenarc customer service, but the only remotely helpful thing that they could hint at was that changing refresh rates "might" help. You can't do that on the Mayflash, but the StarTech can.

Let me know if you have any success. I may just buy one anyway.

Jack

btw what's yr camera & how are you cabling to the StarTech?
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Old November 9th, 2007, 09:17 PM   #4
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For those not familiar with this solution and/or still looking for inexpensive high(er) res monitoring solutions, esp. for pulling focus, here is the thread that got me try it in the first place (sorry it's from dvxuser)
http://www.dvxuser.com/V6/showthread.php?t=82061

and here is a current thread of others continuing to try to test/work it out.
http://www.dvxuser.com/V6/showthread.php?t=103949


Like I said, my original Xenarc/Mayflash combo worked great. But the new one doesn't.

I see similar problems as the one I'm having with the older Lilliputs, but not the Xenarcs. Moreover, the newer Lilliputs that actually have 800x600 resolution (they seem identical to the Xenarcs) have no problems working with the Mayflash. I'm baffled.

The image I get isn't just doubling. I get an overlay of crossbars (sync/phase?) as well. I'll try to post pictures when I can,
-Jack
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Old November 10th, 2007, 06:44 PM   #5
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Jack,

Interesting topic, I read the last thread from your post. I got the impression there were assorted problems, and I was surprised that no one mentioned if the component inputs to the mayflash were terminated to 75 ohms. If the mayflash is not internally terminated, the input signals could ring, causing unpredictable output from the mayflash. If I were dealing with the problem, I would test with the component cables with my own 75 ohm terminations at the mayflash.

Good luck.

Terry
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Old November 10th, 2007, 08:04 PM   #6
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Any ideas?

Thank you, Terry.
Forgive my ignorance. I wish I understood how one might do that. This YPbPr signal stuff is Greek to me.

The component YPbPr signal feeds into the Mayflash unit and the Mayflash has only one VGA output. The Xenarc monitor has only one input, so I assume it's terminated. But...

How would I test that and/or how could I terminate it?

-J

Last edited by Jack Davidson; November 10th, 2007 at 08:13 PM. Reason: whoops
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Old November 10th, 2007, 09:58 PM   #7
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Jack,

Yes, it is a very good assumption that mayflash would terminate the input (would be standard design practice), but when all else fails I start checking the unlikely but possible.

Video is a high frequency signal that can generate signal reflections if it passes an impedance mismatch, kind of like a bump in the road. The cable thinks it is 75 ohms, and it needs to see a 75 ohm path to ground when it enters the mayflash.

Video connectors are either typically BNC (pro) or RCA (consumer). BNC connectors have Tee’s which provide two inputs and one output, which provide the option to add a 75 ohm terminator. But I bet the mayflash is RCA, so to do an inexpensive test I would get three 75 ohm resistors and fashion a way to get one resistor from each center input terminal to ground. Yes, the inputs will patched through with hopefully short exposed wires, thus adding the possibility of noise… but good enough to see if the double scan problem changes.

The best bet is for someone familiar with the Mayflash to jump in and advise us if it is really terminated. I don’t want to send you off on a wild goose chase, you might see if you can find some technical specs from the manufacturer… would be easier. I am not at all familiar with the converter, but I may be soon… this is interesting stuff.

Terry
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Old November 10th, 2007, 11:11 PM   #8
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Great guess. The Mayflash has RCA inputs only.

So let me get this right, I should try to ground each center input terminal, and see if that makes a difference? I'll try it, but it may take a few weeks.

Also, my electronics skills are apparently lacking. See the reason I had to replace the original Xenarc monitor in the first place.

Many thanks, Jack
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Old November 11th, 2007, 01:57 AM   #9
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Jack

The idea is to connect one end of a 75 ohm resistor to the center terminal, and the other end of the resistor to ground. The signal center wire is also connected to the center terminal, and the wire ground goes to the input ground.

Got a better idea, tell me where I can buy one of these mayflash converters and I will test it out. I was planning to get into this anyway.

Terry
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Old November 15th, 2007, 08:57 PM   #10
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Mayflash

Thanks Terry,
Sorry for the delay,I'm back in town now. Here are a few places that sell them in the $50-60 range.

http://www.merconnet.com/product_inf...roducts_id=513
http://www.play-asia.com/paOS-13-71-...n-70-1d2s.html
http://gameforfun.com/en/product.asp?product_id=5120
http://sewelldirect.com/MayFlash-YPb...HV-VGA-Box.asp


Also, if it helps you, I believe this is the guts of it
http://www.national.com/pf/LM/LMH1251.html
The spec sheets are there as well.

FWIW I suspect that the new Xenarc auto detect/scaler is the problem. After all, the previous model worked very well with the Mayflash, as have many other models from other manufacturers.

Thanks, Jack
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