14 January 2013, 22:14 | #1 |
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Joytech PS2 8" lcd to old computers
Hi,
I´m making some cables so I can connect my old computers to a Joytech PS2 8" Lcd. Starting with my Spectrum +3 I made a RGB and a composite cables. With the help of Photon I reach the stage of getting video from the +3 through RGB and composite in the LCD but with some garbage lines on screen (in composite and also in Rgb) like we could see in the 1st and 2nd attachments. I connected a Spectrum 48K by composite signal and the image it´s clear like we can see in the 3rd attachment. Also connected a malfunction +2 by Rgb made the garbage lines too (4th attachment). So I conclude that something is different between the 48k video signal and the +2 and +3 video signals that made te garbage on lcd. Could someone know what could cause and how to clear the garbage lines in the Lcd? Thanks in advance. Last edited by AlfaRomeo; 14 January 2013 at 22:20. |
14 January 2013, 22:57 | #2 |
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Hi,
Try adding 220uF capacitors, in series on the RGB signals. The video output of the Spectrum +3 is DC coupled. This value will be sufficient to pass the colour information through. If the DC offset of the video is too high and the 8" panel has no AC coupling on the input, you will have problems, ahve seen this too often with LCD panels Ian |
14 January 2013, 23:29 | #3 |
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Many thanks Ian, will try that solution.
Besides the DC coupled difference, could exist another differences between the composite video signals of 48K and +3? Last edited by AlfaRomeo; 14 January 2013 at 23:34. |
16 January 2013, 23:24 | #4 | |
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Quote:
Any more ideas? |
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16 January 2013, 23:40 | #5 |
Longplayer
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Maybe some informaton about the Spectrums video out is useful :-
http://www.fruitcake.plus.com/Sincla...SCARTCable.htm Or maybe not :S |
16 January 2013, 23:52 | #6 |
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That extruded line on the second picture makes me wonder if something about the sync is messed up?
Are those errors fixed or do they flicker in random places? |
18 January 2013, 17:29 | #7 |
The 1 who ribbits
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would love see some pics of how you have connected it up and what the rgb wires are connected to, then I might get round to doing my 8" screen as well
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18 January 2013, 21:24 | #8 |
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Hi,
On the Spectrum +3, disconnect R41 (150 Ohm resistor). The 75 Ohm resistor inside the LCD panel, will be in parallel with R41 inside the Spectrum +3, giving a combined terminating resistor of 50 ohms. The sync output voltage will drop from 1.2V to 0.48V. This may be too small a signal for the LCD panel to lock onto and sync strip. It looks like the Spectrum 48K has a 75 ohm output impedance with a standard 1.2V signal, which could explain why the 48K works better. Good luck. Ian |
19 January 2013, 10:49 | #9 | |
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Quote:
But they only jump between these two positions, the lines don´t jump to other positions besides these 2. In screen with movement, eventually, the lines make some drag video artifacts as can be seen in the +2 photo (black with strips). Tomorrow will try to remove the +3 R41 as Stedy says |
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20 January 2013, 16:37 | #10 | |
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Already did that and the garbage lines in the image keeps the same
Quote:
The garbage lines vary only between that 2 positions. |
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21 January 2013, 16:36 | #11 |
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could you try with another +3 PSU? sometimes it can cause bad picture.
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24 January 2013, 01:05 | #12 |
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The problem is that I have only one PSU but already measured the +5v,-12v and +12v in the PSU and all seems ok.
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25 January 2013, 22:54 | #13 |
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Try this
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28 January 2013, 02:01 | #14 |
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maybe the problem is in inverted composite sync signal (why the hell did they invert it?). even though tv only uses phase. can you try amstrad cpc or some console which also has inverted CSYNC?
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20 February 2013, 17:41 | #15 | |
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Quote:
Does any of these computers have inverted CSync?? |
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29 November 2013, 17:37 | #16 |
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So did this experiment ever work out for +3 ?
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