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Old 03 April 2016, 15:57   #1
asapreta
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Problem with Scandoubler: vertical bars

Hi guys.

I have an Scandex Scandoubler and its behaving oddly.

I attached to 22" LCD Monitor and got vertical bars. So I decided to use it on my LG 1721a Flatron (15Hz capable monitor) and got these:

Using the Scandoubler and selecting monitor's 15Hz mode:



Using the Scandoubler and selecting monitor's VGA Mode:



Composite mode: (obs: the bluish color is probably my mobile cam distortion)



Using a RGB cable (15hz) - No scandoubler:




The 15Hz image using the scandoubler should not be dark, at least the same as the same as the VGA mode.

Do you guys can try to help me out please, where should I start checking it?
I have good electronic skills and equipment.

Best Regards
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Old 03 April 2016, 19:00   #2
Daedalus
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First off, make sure the grounding is ok everywhere that it should be - cable and scandoubler.

Have a look at the power supply to the scandoubler on an oscilloscope. It's possible there's some sort of interference from something else nearby that's causing the repeating patterns. It would most likely be a video clock as the lines are synchronised with the horizontal clock. To confirm if a clock is causing the interference, put one of the RGB outputs (I would say red would be the best bet as it is showing the most interference in those photos) on the second channel of the scope and look for similarities between the two signals.
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Old 03 April 2016, 19:04   #3
hooverphonique
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Interference, bad connection, or a bad passive component (likely a capacitor), I'd say.
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Old 03 April 2016, 20:26   #4
asapreta
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Quote:
Originally Posted by Daedalus View Post
First off, make sure the grounding is ok everywhere that it should be - cable and scandoubler.

Have a look at the power supply to the scandoubler on an oscilloscope. It's possible there's some sort of interference from something else nearby that's causing the repeating patterns. It would most likely be a video clock as the lines are synchronised with the horizontal clock. To confirm if a clock is causing the interference, put one of the RGB outputs (I would say red would be the best bet as it is showing the most interference in those photos) on the second channel of the scope and look for similarities between the two signals.
Thanks for the tip. I'll do that.

While I was testing I managed to get better images manually configuring my monitor and changing its clock adjustment. Take a look:



(The bluish images are my mobile cam distortion)




I also noticed it got a little cleaner when I connected this device, a CVBS converter. It drops the signal a bit:



But will hook to an osciloscope and see the clock.
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Old 04 April 2016, 14:30   #5
utri007
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Join Date: Nov 2001
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I have excatly same problem.

However my problem is both of my scandoublers. I haven't tested with my other A1200 Computers. But I quest that tells that problem is with Amiga, not a scandoubler.

http://amiga.resource.cx/exp/scanmagicint
http://amiga.resource.cx/exp/scandy1200
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