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Old 13 April 2020, 17:14   #1
Per Hansson
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Amiga 3000 vertical bars (jail bars) via VGA normal?

Hi, I'm fixing up an A3000 on a friends request:
Fixing a (very small) battery leakage and replacing the caps on both the board and power supply.
The board has a perfect RGB video output via the 23-pin video connector to SCART.
And it also looks good on a CRT monitor via VGA.
But the VGA output has some vertical bars or jailbars as they are also called on LCD's.
I tested with 3 different LCD monitors and they all produce very similar results:
Acer AL1716, Dell 1907FP, Eizo Flexscan S2000 and a Panasonic Plasma.
With the standard settings there are evenly spaced vertical bars in the picture.
Now on the Eizo I can adjust it so the image becomes pretty much perfect.
But the other monitors do not have enough adjustment range to make the bars go away.
Now all I am wondering is if this behavior is normal or not?
I did allot of Googling on this but I am still not convinced either way.
Here are the settings used with the Eizo monitor to make the picture good:
Code:
NTSC:
Clock 800 > 910
Phase 0 > 58
Resolution 640x480 > 744x486
Smoothing 3 > 1
Signal filter 3 > 1

PAL:
Clock 1024 > 1362
Phase 0 > 58
Resolution 800x600 > 1136x580
Smoothing 3 > 3
Signal filter 3 > 1
The board has been washed then thoroughly cleaned in IPA.
And all chips have been removed and cleaned individually.
There was quite some crud on the board, some parts even required acetone to be cleaned properly.
But all in all this has not had any effect on how the display looks.
Adjusting VR470 or VC470 does not affect the bars.
Replacing the caps in the PSU and board also had no discernible difference.
Attached Thumbnails
Click image for larger version

Name:	Acer AL1716 VGA.jpg
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Size:	466.6 KB
ID:	66836   Click image for larger version

Name:	Dell 1907FP VGA.jpg
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Size:	519.1 KB
ID:	66837   Click image for larger version

Name:	Eizo Flexscan S2000 VGA.jpg
Views:	87
Size:	357.8 KB
ID:	66838   Click image for larger version

Name:	Panasonic Plasma VGA.jpg
Views:	77
Size:	171.7 KB
ID:	66839   Click image for larger version

Name:	Panasonic Plasma RGB SCART.jpg
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Size:	151.7 KB
ID:	66840  

Click image for larger version

Name:	IBM G74 CRT VGA.jpg
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Size:	359.4 KB
ID:	66841   Click image for larger version

Name:	Eizo Flexscan S2000 VGA Adjusted.JPG
Views:	92
Size:	198.0 KB
ID:	66842  
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Old 13 April 2020, 17:28   #2
jotd
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yes, I have a scandy scandoubler, and those vertical lines are displayed.

If you have a scandoubler I think that it's normal.

Some LCD monitors can display 15Khz vertically through VGA (like ACER K242HYL, which is cheap, but the display isn't perfect). There are others mentionned in this forum. Like that one (not tested personally): Dell U2412M: http://eab.abime.net/showthread.php?t=85693
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Old 13 April 2020, 17:28   #3
DarrenHD
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I think it is normal is it not?
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Old 13 April 2020, 17:30   #4
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In my experience with various flicker fixers with VGA output, this is pretty normal, and the adjustment range on most monitors doesn't suffice to make the effect disappear completely.
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Old 13 April 2020, 17:32   #5
LucasBox
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This is normal on LCD and belongs to the pixelclock. Some LCDs or brands like Eizo can handle ist better than others.
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Old 13 April 2020, 18:06   #6
Per Hansson
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Thank you for your replies!
Yes the scandoubler is built into the A3000, it is the Amber chip in it.
I guess the third party scandoublers that can be bought for other Amigas are based on this original Commodore design?
At least now I can stop trying to fix this issue, if it is supposed to be like that
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Old 13 April 2020, 18:18   #7
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I wouldn't go as far as to say that all flicker fixers are based on the Amber design, but they all implement the same basic principles and thus suffer from the same basic flaws.
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Old 13 April 2020, 21:22   #8
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Thanks, yes it is what I implied
Another related question, with a monitor that can display the 15kHz VGA signal:
Will that then not have the problem with the vertical bands/bars/lines?
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Old 14 April 2020, 00:56   #9
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It does not matter if 15 or 31 kHz with flickerfixer the Problems are the same. Both will have vertical lines. There only a few monitors which can handle this issue. I brought a NEC MultiSync EA192M (15 kHz) where the lines are almost invisible.

Last edited by LucasBox; 14 April 2020 at 10:16.
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Old 14 April 2020, 01:27   #10
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monitors must handle 15KHz vertically and 50Hz horizontally Else only NTSC games will work.

A second monitor is always handy for another machine when the amiga isn't in use. I'm using the ACER as a second screen for my laptop in HDMI when the CD32 isn't running (plugged on the VGA port).
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Old 14 April 2020, 08:09   #11
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I wanted to say the Eizo shots are beautiful and makes the Amiga look amazing. There is reason why Eizo monitors are worth their money. They are still at the old Sony levels with high quality tuning and parts in their products.
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Old 14 April 2020, 12:44   #12
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And just to be sure, the lines are not in the signal, they happen when the monitor makes an assumption about the analogue signal and tries to sample it at pixel boundaries to make a resolution it thinks it is sensible.

The Amiga does not output a sensible (in terms of VESA standards) resolution, so the sampling will almost always fail and you must adjust the width/clock/phase settings manually.
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Old 14 April 2020, 14:18   #13
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It obviously won't help with the VGA output but with the Arananet RGB 'amplifier' adapter you can get rid of almost all of the jailbars with the regular RGB port when used with a 15khz capable display. I use it with the Benq 702a.
https://www.arananet.net/pedidos/pro...rgb-amplifier/
Basically it makes it possible to use any of the modes that by default would have a really bad jailbar effect. In those cases the analog to digital sampling is still not 100% correct so you would have slight blurring and slightly off aspect ratio instead but it will look much cleaner.
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Old 19 April 2020, 14:51   #14
Per Hansson
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Thank you all for your input on this!

dodke: in my first post there is a link to a photo called "RGB video output" this is the Panasonic Plasma, a TH-37PX80E connected via SCART and it looks great!
I then hook the same Panasonic Plasma up via VGA and the result is really poor.
You all have have helped explain why that is really well and I hope this thread can help someone else Googling this issue like I was in the future.

Valken: yes I agree, but also it is extremely difficult to photograph the Eizo and give it justice.
In my first post above it looks like there are some lines even after adjusting the Eizo's pixel clock but in reality I can not see them!
So here is another picture attached, with identical monitor settings, I will not tell how long it took to get this result with my DSLR camera
Now this Amiga 3000 will be heading back to its owner, battery fixed and several other misc issues, plus it now has a new Kickstart
Attached Thumbnails
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Name:	Eizo Flexscan S2000 VGA Adjusted2.JPG
Views:	81
Size:	221.9 KB
ID:	66933  

Last edited by Per Hansson; 19 April 2020 at 17:04.
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