07 June 2011, 21:37 | #161 |
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Hi,
Only two reasons for a white screen I can see, the first has already been covered (Composite video only SCART). The other possibility is that the RGB mode pin (pin 16) is for some reason missing or at the wrong voltage. With my design and a properly terminated input there should be 2.5V, which I measured during my tests. If the voltage on pin 16 <0.4V, the TV will select the composite video signal on pin 20. The Amiga does not have a composite video signal on the 32 way connector and the TV interprets the signal as a peak white video level as it is approx 1V. I developed this cable design based upon a reference schematic for one of the analogue video decoder devices commonly used in TVs/monitors, to satisfy all signal levels it could accept. Ian |
07 June 2011, 22:33 | #162 |
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I would measure the voltage on pin 16 (compared to pin 18) while its connected to TV, if possible.
perhaps pin 18 is not connected properly? |
09 June 2011, 02:14 | #163 | |
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Thanks guys, I'll just order a couple of these from amigakit then..
Another thing - just to make sure after reading this part again: Quote:
Thanks again! |
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09 June 2011, 03:08 | #164 |
PSPUAE DEV
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05 September 2011, 19:56 | #165 |
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I built your cable to the specs except i didn't solder SWITCH cable or R/G/B ground since it was a test and i only had 10 scart pins.
Works great though. Both on my CRT 28" and a Viewsonic N2060W-1e LCD TV. Also i used a 397 Ohm instead of 333 and a 1,18 kOhm instead of 1k resistors. Just because that was what i had at home. Don't know if it affects quallity. Interlaced mode is stable, flickers a bit when stuff move around the screen, nice picture quality, i'll test with all the ground cables soldered also when i get the connector. Thanks! |
09 September 2011, 22:16 | #166 |
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@Magge
Glad the cable design worked well. You can very the resistor values by around 10% and it should work well. @thread I tested my new LG LCD TV, got a nice picture on it: Both normal and interlaced modes were handled without issue. PAL/NTSC was no problem. I had designed a filter PCB, to filter out a 9 MHz noise component from the DAC output of the A1200. Installed it and tested it, it made absolutely no difference! Finally, I tried plugging my cable into a composite/CVBS only socket. With the default TTL CSYNC option, I had a black screen. Using the Composite video output of the A1200 as the sync source, I got this naff picture: That's all for now. Ian |
10 September 2011, 10:51 | #167 |
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to me, colours on CVBS picture look better, esp yellow (too 'cold' on RGB). did you change some tv settings? perhaps its the camera.
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16 October 2011, 22:12 | #168 |
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Hi,
I've just bought an LKV362 (http://www.lenkeng.net/Html/Product/...CONVERTER.html) and I think I have the same problem as Ferix I've made the SCART cable using all resitors and checked it with two LCD TVs I have. It works fine, but all started because my 41" LCD tv introduces too high delay and playing games with the Amiga is impossible. So I decided to give a try at this SCART->HDMI adapter but I can't get a picture out of it. Well, the only way I found to see something is to use the Amiga DB23 port but composite-sync from the RCA composite-video connector (I'm using an Amiga 1200). In this way the LKV362 is able to show me a picture, albeit with some noise and shadows. Funny is , if I disconnect the DB32 from the amiga and I reconnect it with all other cables connected, the noise-shadows disappears. My guess is that this device doesn't like Amiga sync signal from DB32 port. The decoder that gets the RGB or composite-video signals is a TI : http://www.ti.com/product/tvp5160&lp...native_Devices I'm not the greates expert on video signals, so maybe Stedy/Ferix or someone else on the board can help to shed some light on this? With above trick seems to work nice, it's cheap and would be the perfect device to finally make that Skidmarks tournment on my 41" LCD that I promised to my friends Thx - Cheers -- LuKe |
17 October 2011, 04:25 | #169 | |
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Quote:
I love how clean that first snapshot looks, Ian. Even if it wasn't the 'best' signal, I rather liked the built-in blending of composite back in the day for gaming - but I'd have loved that sort of quality elsewhere. I don't think I was imagining twenty or so years ago that in Space Year 2011 we'd be seeing an Amiga picture like that on a futuristic flat-screen display! Wow, they'll be making mobile communication devices that let you hold conversations away from home - and with no cables - next! |
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18 October 2011, 03:46 | #170 |
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Thanks for posting this schematic. My brother soldered one up for an Amiga that had broken RF and composite. Cost about £7 and worked perfectly. Great picture quality, noticeably sharper than composite.
It worked with CRT, but not a PAL LG LCD TV. We used the resistors exactly as given on the diagram but didn't wire the composite because that Amiga's composite was broken anyway. |
19 October 2011, 00:01 | #171 |
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Hi,
With regard to the photos of my TV. The difference in the appearance of the pictures was most likely due to the camera. I am still learning how to use my new camera though the fluorescent lights of the workshop do not help. The RGB video text was much much clearer. Now on CSI, they would find the 2 pixels, in the reflective plastic and from that reconstruct my face @LukeJerry/Jonathan Drain The Amiga's video sync is not compliant with either the PAL or NTSC specifications in non-interlaced mode and is better in interlaced mode, not ideal for games. Some TVs can not handle the non-standard Video sync. If the TV can handle a VCR playing back a macrovision protected video tape, it should work better with the Amiga. Am I the only one here who still has a VCR? Bye, Ian |
19 October 2011, 14:14 | #172 | ||
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@Stedy
1st of all thanks a lot for the help and your page/post on SCART cable for Amiga! I see Amiga video sync is not very compliant, I've tried anyway to set an interlaced video mode with my A1200 connected to this Lenkeng converter but the result is the same (some signal is detected but black screen). In a previous post you said: Quote:
http://www.ti.com/lit/ds/symlink/tvp5160.pdf Quote:
Seem from the data sheet that this "fast switch" mode can be disabled, I hope to find some time next days to try modding this box and disable it. -- LuKe |
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01 November 2011, 23:14 | #173 |
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@LuKeJerry,
The fast-switch mode is controlled by pin 16 of the SCART socket. I feed 5V via a potential divider to set 2.5V @ the TV. This forces the TV into RGB only mode. There is no need to disable the fast-switch mode, my cable does that. The device could be blending the CVBS and RGB signals, this can be disabled by an I2C register write or two. I'll leave that up to you. Ian |
06 November 2011, 15:55 | #174 |
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Hi,
Stedy, i made 2-3 scart cables and tested with my AMIGA 500 but i used only one cable for all the grounds(amiga pin 16->scart pin 17) . Also i didn't use pin 8 of the scart to autoselect av (as almost on any tv, crt or lcd, you can choose "av" from the remote control) . Also instead of connecting 5volt to pin 16 of the scart i took the 12 volts from pin 22 of the amiga connector and through a 1ΚΩ resistor i put it on pin 16 of the scart. Finally i used a 330Ω resistor on the CSYNC as you suggest (amiga pin 10 to scart pin 20).(this was from a design i had, before i saw your site - btw, congratulations for you excellent analysis on the subject!) When i connected the cable i measured the following voltage levels on the scart pins: pin 16: 0.83volt pin 20: 0.67volt (My amiga 500 outputs 4.34volt on pin 10 where scart pin 20 is connected) All cables i made (even one without the 330Ω resitor) have worked perfect on 3 tv sets i have, 2 crt's and 1 lcd. So my questions are: 1) I've made some measurements with a poly meter on the various ground pins on both amiga 23 pin and scart connectors (on 2 crt tv's and one lcd tv). What i found out is, that ALL ground pins on amiga are internally connected (short circuited) but also ALL ground pins on the scart connectors (at both 3 tv's) are internally connected! So my question is, why use 5 different separate "ground" cables when actually there is only ONE ground on both amiga and scart connectors? 2) If a scart video cable works on a particular tv with an amiga 500, this means that it will also works with every amiga (600,1200,3000,4000)? That is, are there any differences on levels of CSYNC (or other signals too) between various amiga models that will require different resistors or pinout? 3) i gave one of my cables (with the 330Ω) to a guy that has an A4000 and told me that he got picture, but has something like "shadowing". He tried another cable form amigakit and works ok. So, where do you think is the problem with my cable? Is the 0.83volt on scart pin 16, too low to clearly select rgb? Or the 330Ω dropped the signal too much on the A4000? Or what? 4)I noticed on the crt tv's , that when i didnt connect the 2 audio rca to the amiga, i had a slight horizontal "noise band " that keep moving upwards on the screen. This disappeared when i connected the 2 audio rca. What can cause this? Thanks. Last edited by ikonsgr; 06 November 2011 at 16:18. |
06 November 2011, 17:19 | #175 |
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1) because of interference/crosstalk.. and I think not all grounds are connected.
2) iirc, they are all the same. 3) perhaps cable too long. or bad ground. 4) also ground |
06 November 2011, 20:46 | #176 | |
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Thanks for your reply orange, but i still cant understand some things...
Quote:
Cable was only 1.5meters long(brand new shielded 6 branch low loss), and with my amiga 500 worked perfect on all 3 tv's! How can it be "bad ground" to his Amiga and "good ground" to mine? If we assume it was the guy's tv fault then neither amigakit's cable should work, but it does! On the other hand,if we assume that it was not tv's fault and since my cable work perfect to my amiga, then according to your answer to my second question, it should be working also for A4000. Go figure... Can you be more specific about that? You mean that i had a bad soldering or something? Keep in mind that i used separated cable for the audio ground (in fact it was the shielding of the 2 coaxial cables i used for the 2 audio rca connections). As far as the cable concerns, i measured all impedences for every connection (pin to pin) and found out it was below 0.1 Ωm (the limit of my ohm meter) |
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06 November 2011, 21:25 | #177 |
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crosstalk and interference are in the cable itself. for same reason IDE, SCSI and floppy cables have bunch of GND pins/wires.
well, I have the same issue 4) I think its because audio uses Shielding as GND. (and shield should be definitely different from RGB signal GND) so perhaps try connecting 23pin port shield to SCART? BTW, iirc, low resistance doesn't necessarily mean short circuit. coils have low resistance. Last edited by orange; 06 November 2011 at 21:43. |
07 November 2011, 11:17 | #178 |
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Hmm, that thing with the coils you said, i didn't thought about it, you are right, it is possible....
So you think, that if i use a, lets say 10 branch cable, to connect every ground separate, then i will get a more clean picture than with the current cable? I suppose that any differences will be more visible with LCD tv's and with workbench environment and not with games, right? Maybe that's the case, because my testing was made mostly with games (where small ghosting/shadowing or other minor defects in picture quality is difficult to detect). However in workbench or any more intensive "video reading" application, where clarity and distinctness of picture is very important the separate ground will make a difference. |
07 November 2011, 11:59 | #179 |
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I think its worth trying out. iirc, you'd only need 3 of them, one GND for each R,G,B. and one more for audio (though that one might be unnecessary if you already connected the shielding).
I remember seeing factory made SCART<->SCART cable (but without connectors). it was designed to be extender, connecting all 21 pins. and it was obvious that each R,G,B signal was shielded with its GND. one more thing about shielding, they say one shouldn't connect it at both ends (in null-modem cables, for eg.) to avoid (ground) loops that pickup noise or something like that. have you connected it to SCART pin 21? |
07 November 2011, 16:00 | #180 |
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Well according to stedy's design http://www.ianstedman.co.uk/Amiga/am...iga_scart.html i will need 11 pins but my cable has 10 branches...
Except from R,G,B you will also need separate grounds for pin 20 of the scart (where CSYNC pin 10 of amiga goes) and also for pin 16, the RGB selection. I think the most "essential" ground is pin 17 (the CSYNC/ composite video ground) since the other design i had ,with only one ground connected,was using this pin for all the grounds. You think i can overlook, lets say, RGB select ground without any compromise in picture quality?Or maybe don't connect pin 8 of scart, since all tv's can select "AV" from the remote control... I will also try what you say, connect the shielding on both ends to see if there is any difference. |
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