TheRaven81 Posted June 27, 2021 Share Posted June 27, 2021 ok - dug really hard and found this post here: https://atariage.com/forums/topic/198754-current-best-s-video-picture-improvement-mod-for-800xl/?do=findComment&comment=2534448 which seems simple enough. Can someone clarify it with pictures though, so I know where to look/what to do for each step? Quote Link to comment Share on other sites More sharing options...
AirKon Posted June 27, 2021 Share Posted June 27, 2021 I made this drawing to help me. but it's in french, but it must be understood. Quote Link to comment Share on other sites More sharing options...
hasanc Posted June 27, 2021 Share Posted June 27, 2021 Step 3 in 800XL NTSC: Quote Link to comment Share on other sites More sharing options...
flashjazzcat Posted June 27, 2021 Share Posted June 27, 2021 42 minutes ago, hasanc said: Step 3 in 800XL NTSC It's missing the 100R resistor. 1 Quote Link to comment Share on other sites More sharing options...
TheRaven81 Posted June 27, 2021 Author Share Posted June 27, 2021 (edited) 1 hour ago, flashjazzcat said: It's missing the 100R resistor. why do you say it is missing if that step says it doesn't need one of any kind? (you'll have to excuse me, i'm not a huge Electronics person.) Edited June 27, 2021 by TheRaven81 Quote Link to comment Share on other sites More sharing options...
flashjazzcat Posted June 27, 2021 Share Posted June 27, 2021 42 minutes ago, TheRaven81 said: why do you say it is missing if that step says it doesn't need one of any kind? Because the resistor is needed for the correct chroma signal strength: 2 Quote Link to comment Share on other sites More sharing options...
TheRaven81 Posted June 27, 2021 Author Share Posted June 27, 2021 (edited) 4 hours ago, AirKon said: I made this drawing to help me. but it's in french, but it must be understood. Translated to English (via the Google Translate app on my phone) - wondering if it's correct (if i'm going to follow this, I don't want it to be wrong) Edited June 27, 2021 by TheRaven81 Quote Link to comment Share on other sites More sharing options...
Faicuai Posted June 27, 2021 Share Posted June 27, 2021 7 hours ago, TheRaven81 said: ok - dug really hard and found this post here: https://atariage.com/forums/topic/198754-current-best-s-video-picture-improvement-mod-for-800xl/?do=findComment&comment=2534448 which seems simple enough. Can someone clarify it with pictures though, so I know where to look/what to do for each step? Here you go, click directly on "shannesh replied..." caption (with results as seen on CRT): And chroma-pickup point and termination, underside: (post right above here. NOTE: please route chroma-cable around shield-pad, and through lower shield-plate opening, so your shields don't smash it, and can also be installed back properly) You will not need any resistor, on the chroma line. You may be surprised to learn or discover that, even in seemingly identical machines, with identical MoBo revisions, keyboards, place of manufacturing. and near dates of production, chroma response at that pickup-point could vary considerably (one stronger and the other substantially weaker, for instance). Therefore, it turns out to be effective or practical to adjust final color level via [TV / monitor / processor] own color/saturation adjustment. Enjoy! Quote Link to comment Share on other sites More sharing options...
flashjazzcat Posted June 27, 2021 Share Posted June 27, 2021 Nevertheless, on average, the 100 Ohm resistor makes colour output broadly consistent with that of other machines (600XL, 130XE, XEGS, etc). This is great since it saves me having to fiddle with colour controls on the TV every time I swap machines. YMMV. 1 Quote Link to comment Share on other sites More sharing options...
TheRaven81 Posted June 27, 2021 Author Share Posted June 27, 2021 (edited) 3 hours ago, flashjazzcat said: Nevertheless, on average, the 100 Ohm resistor makes colour output broadly consistent with that of other machines (600XL, 130XE, XEGS, etc). This is great since it saves me having to fiddle with colour controls on the TV every time I swap machines. YMMV. OK, so which type do I get, and at what watt/tolerance? looking for them I see so many different kinds. Edited June 27, 2021 by TheRaven81 Quote Link to comment Share on other sites More sharing options...
flashjazzcat Posted June 27, 2021 Share Posted June 27, 2021 1/4W carbon film, 1% will work. 1 Quote Link to comment Share on other sites More sharing options...
hasanc Posted June 27, 2021 Share Posted June 27, 2021 9 hours ago, flashjazzcat said: It's missing the 100R resistor. I didn’t know, I’ll install one. Thanks! Maybe it’d explain why colors look a bit washed out in my 800XL. 2 Quote Link to comment Share on other sites More sharing options...
TheRaven81 Posted June 27, 2021 Author Share Posted June 27, 2021 1 hour ago, flashjazzcat said: 1/4W carbon film, 1% will work. Is the tolerance a big deal at all? I'm looking for a resistor with these specs, but I can only find 5% tolerance, not 1%. Quote Link to comment Share on other sites More sharing options...
Faicuai Posted June 27, 2021 Share Posted June 27, 2021 26 minutes ago, hasanc said: why colors look a bit washed out in my 800XL. For me, it was puzzling, to say the lesst. Two seemingly identical machines (inside / out): same MoBo revision, same PCB color, same integrated resistor-pack color (red) on the right side near PIA ports, same ALPS type-1 keyboard, both fully socketed, same manufacturing place, pretty close serial #s: The unit at the bottom (my original gift in 1984), produces a STRONG, rich color output... and the unit at the top (which I bought as back-up, and found it really cheap and intact) produces a much leaner, less denser color reproduction. The color-adjustments required to bring these units to an equivalent color-saturation reproduction are quite different. In my case, when first testing the chroma-line resistor, I could not normalize color response with it, leading me to adjust color-saturation externally, anyway. Therefore, and for just practical reasons, I did not use them, and let anyone adjust color saturation as they deemed fit. Whatever the case, YMMV, no doubt about it. Good luck! 1 Quote Link to comment Share on other sites More sharing options...
flashjazzcat Posted June 27, 2021 Share Posted June 27, 2021 7 minutes ago, TheRaven81 said: Is the tolerance a big deal at all? I'm looking for a resistor with these specs, but I can only find 5% tolerance, not 1%. I wouldn't worry - 5% will do. 1 Quote Link to comment Share on other sites More sharing options...
hasanc Posted June 27, 2021 Share Posted June 27, 2021 1 hour ago, Faicuai said: The unit at the bottom (my original gift in 1984), produces a STRONG, rich color output... and the unit at the top (which I bought as back-up, and found it really cheap and intact) produces a much leaner, less denser color reproduction. It might be my case as well (800XL NTSC). I'm curious now, I'll check the voltages and try to match these values: https://www.maximintegrated.com/en/design/technical-documents/tutorials/1/1184.html NTSC S-Video PAL S-Video Setup 53.57mV Setup 0mV Y 714.29mV (Peak Luma, 100% White) Y 700.00mV (Peak Luma, 100% White) C 626.70mVP-P (75% Color Bars) 835.60mVP-P (100% Color Bars C 663.80mVP-P (75% Color Bars) 885.10mVP-P (100% Color Bars Sync -286.00mV Sync -300.00mV Quote Link to comment Share on other sites More sharing options...
Faicuai Posted June 27, 2021 Share Posted June 27, 2021 37 minutes ago, hasanc said: I'll check the voltages and try to match these values: You may find crazy-level signals (eventually normalized by your video processor or terminal screen interface auto-gain if present)... and in the case of the 800XL, contamination of Y-signal (sVideo) by vestigial chroma signal coming from C54-juncture (that is what the red-switch us used for, to mostly isolate the Y-signal from the Y+C combing stage). All here, under the scope (including 800 signals, as reference): Happy hunting! 1 Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted July 9, 2021 Share Posted July 9, 2021 (edited) the value of 75 ohm through 100 ohm is correct. the XL's sometimes had close enough resistors etc used at manufacture. You need the resistor for correct output levels matching impedance correctly... FJC is correct in that 100 ohm is way closer to reality than zero ohms that's for certain! I'd add the resistor ... Edited July 9, 2021 by _The Doctor__ Quote Link to comment Share on other sites More sharing options...
+Peter Rabitt Posted July 10, 2021 Share Posted July 10, 2021 I have a question and I do not think it is one asked before.... Why add a tantalum capacitor on the collector of the Q3. Could a Electrolytic Capacitor work. Is the noise/freq. that high?? The upgrade changed the collector resistor to 2.2 ohms. Not much signal left to bypass...??? If you have done this did it help the video??? Just thinking WHY!!! The gain for this stage has increased a fair amount with the lower collector resistor and the lower resistor in the emitter .. And yes I agree about the resistors in the series of the lum/corm. ckts as it will also add to the noise reduction..Matching impenitence helps.. I maybe using this to maybe upgrade my 800xlI just got going again.. Peter Quote Link to comment Share on other sites More sharing options...
Mazzspeed Posted July 10, 2021 Share Posted July 10, 2021 1 hour ago, Peter Rabitt said: I have a question and I do not think it is one asked before.... Why add a tantalum capacitor on the collector of the Q3. Could a Electrolytic Capacitor work. Is the noise/freq. that high?? The upgrade changed the collector resistor to 2.2 ohms. Not much signal left to bypass...??? If you have done this did it help the video??? Just thinking WHY!!! The gain for this stage has increased a fair amount with the lower collector resistor and the lower resistor in the emitter .. And yes I agree about the resistors in the series of the lum/corm. ckts as it will also add to the noise reduction..Matching impenitence helps.. I maybe using this to maybe upgrade my 800xlI just got going again.. Peter The capacitor softens the image ever so slightly. I added the 100 ohm resistor as well as the 220 microfarad capacitor to my 600XL and the resulting picture quality was actually quite impressive. Even software 80 columns looked good: Quote Link to comment Share on other sites More sharing options...
+Peter Rabitt Posted July 11, 2021 Share Posted July 11, 2021 Mazzspeed: What do you mean " softens the image ever so slightly. " Did you see something on a scope or just the effect on the monitor. Sorry but I missed the 100 resistor and the 220uf cap. Where did you put it?? Sorry for asking all the questions but I have looked at the ckt and see what other people have said and done and just want to do the best of them all by adding or subtracting the changes everyone has suggested... Going to start today... Your picture looks real good!!! Peter Quote Link to comment Share on other sites More sharing options...
+Peter Rabitt Posted July 12, 2021 Share Posted July 12, 2021 Well I just had fun modding the 800xl to the "updated" video output.. I did do some testing after each change.. If nothing else as most of the people here have said DELETE C56 It does the most to change the output as far as the s-video is. I did the c56 first and check with a scope and the delay in sig. is very apparent.. From vertical lines to slope with the c56 in... I did just unsoldered one of the leads so I could "push" it down to make contact and what a change... The test video was the self test and what a change... I have not tried the 10uf cap on the collector of Q3 yet as I have to get one from somewhere. I did all the changes on the 800xl that where in this thread, I think LOL On to the next problem should I add more memory or leave it at 64k??? If more that is the most usable update, not the most memory for barging rights of memory but the usable.. Peter Quote Link to comment Share on other sites More sharing options...
deffroe Posted October 29, 2022 Share Posted October 29, 2022 Sorry if this is a stupid question but...S-Video is pretty rare in the UK I believe, so, if the 800XL is going to only be used in composite is there any benefits to performing the mod? Phil Quote Link to comment Share on other sites More sharing options...
manterola Posted October 29, 2022 Share Posted October 29, 2022 (edited) S-Video as a connector probably is super rare. But S-Video as a concept is present in the SCART connector. There is one mode in which the SCART connector accepts Lumma+Chroma, instead of composite, just Google for SCART Atari or variations and you should find it. In conclusion, enabling the S-Video (or lumma + chroma) output will help you to get a better video quality from your Atari computer. Edited October 29, 2022 by manterola Quote Link to comment Share on other sites More sharing options...
Beeblebrox Posted October 29, 2022 Share Posted October 29, 2022 Svideo output always looks far better on modern LCD screens than composite in my experience. I always hook up chroma for svideo on all my stock 800XLs by default. Case in point FJC demonstrates here the difference you can see on composite vs svideo: 1 Quote Link to comment Share on other sites More sharing options...
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