jmetal88 Posted February 21, 2014 Author Share Posted February 21, 2014 Dang it, smrty pents! lol, now I gotta rip my intellivision apart to check on the 33ohm resistor. I used a 1/4W one there Mind you, it would get hot if it was putting that much current through, wouldn't it? So, you fed 5v into the video input feed to the av mod circuit? I'll update my original post with this info Yeah, it would get quite hot dissipating that much power. Like I said, there might be something else limiting the current that I don't know about, so it may be perfectly safe (I just didn't want to chance it). I fed the 5V output of the regulator through a 470-Ohm resistor (I didn't have a potentiometer to try different values, but 470 Ohms looks good enough, to me) and to the video input of the mod circuit. I'm using the same regulator to feed power to the 2N3904 circuit as well, by the way. 1 Quote Link to comment Share on other sites More sharing options...
exodave Posted February 24, 2014 Share Posted February 24, 2014 Alright, I gave the video mod its own 78L05 rather than tapping 5V straight from the board and now the picture is rock-solid! There is some very, very minor ghosting, but the 'shimmering' I mentioned in my last post is completely gone. It's certainly at least as good a picture as the RF was when hooked straight to my CRT set. The way I've got this set up would make an interesting case for a drop-in replacement for the RF modulator. It doesn't use any connection points on the board that the original RF modulator didn't use, and for the output jack I just used a 3.5mm stereo headphone jack mounted where the RCA jack used to be so that the case doesn't need modification. I just need to use a headphone to RCA breakout cable to the TV. If I use an audio cable, I get audio on the white plug and video on the red plug, but it also works with the video out cable from my digital camera, with video on the yellow plug and audio on the black plug. jmetal88, can you describe the changes you made in regards to this diagram from Solarfox's tutorial? I'm assuming all the differences are in that top part. Quote Link to comment Share on other sites More sharing options...
jmetal88 Posted February 24, 2014 Author Share Posted February 24, 2014 jmetal88, can you describe the changes you made in regards to this diagram from Solarfox's tutorial? I'm assuming all the differences are in that top part. Gimme a bit and I can draw a new schematic. Quote Link to comment Share on other sites More sharing options...
exodave Posted February 24, 2014 Share Posted February 24, 2014 Awesome thank you! Quote Link to comment Share on other sites More sharing options...
jmetal88 Posted February 24, 2014 Author Share Posted February 24, 2014 Okay, this schematic is exactly the way I have mine built (not including the connections to the 3.5mm stereo jack). 1 Quote Link to comment Share on other sites More sharing options...
HunterZero Posted February 25, 2014 Share Posted February 25, 2014 Seems reasonable but a little excessive to add another voltage regulator. It's possible the +5V you previously tapped from the board wasn't the ideal place to do it and had a pulse/ripple on the voltage that caused the shimmer. If you have an oscilloscope (I don't have one, but I'm started to think about getting one, they're invaluable for this kind of thing), you should be able to find a clean +5V on the board nearer the power ribbon. - J Quote Link to comment Share on other sites More sharing options...
jmetal88 Posted February 25, 2014 Author Share Posted February 25, 2014 Seems reasonable but a little excessive to add another voltage regulator. It's possible the +5V you previously tapped from the board wasn't the ideal place to do it and had a pulse/ripple on the voltage that caused the shimmer. If you have an oscilloscope (I don't have one, but I'm started to think about getting one, they're invaluable for this kind of thing), you should be able to find a clean +5V on the board nearer the power ribbon. - J Nah, I like the idea because it means I'm not tapping anywhere that the original RF modulator wasn't tapping. That circuit is effectively a drop-in replacement for the RF modulator. Besides, I have 5V regulators just laying around for some reason, might as well use one of 'em. Quote Link to comment Share on other sites More sharing options...
HunterZero Posted February 25, 2014 Share Posted February 25, 2014 How hot does the 78L05 get? You might need some additional filter caps around the regulator to really make the voltage stable. That may get rid of the ghosting. Do you have a 'scope? - J Quote Link to comment Share on other sites More sharing options...
jmetal88 Posted February 25, 2014 Author Share Posted February 25, 2014 (edited) How hot does the 78L05 get? You might need some additional filter caps around the regulator to really make the voltage stable. That may get rid of the ghosting. Do you have a 'scope? - J Well, the interesting thing is there's ghosting on my video monitor, but not on my TV. There's also ghosting from my Atari ST on my video monitor (it puts out PAL, so I can't test it on my TV). So there may just be something wrong with my video monitor. Anyway, it doesn't bug me too much (and there was a ton more ghosting on the RF output than on this video mod). I haven't tried to feel the temperature of the 78L05, I just kind of put it in hoping it would work, and it did. EDIT: I do have an oscilloscope, but both of my probes are broken right now (that's what I get for buying the cheapest probes I could find off eBay). Edited February 25, 2014 by jmetal88 Quote Link to comment Share on other sites More sharing options...
ZarK Posted February 25, 2014 Share Posted February 25, 2014 (edited) If the 33Ohm resistor didn't over heat, I suspect the 7805 should be able to run without a heat sink. Edit: Oh, the 78L05 is a tiny lil' guy and not the to-220 case the 7805 is Edited February 25, 2014 by ZarK Quote Link to comment Share on other sites More sharing options...
ZarK Posted February 25, 2014 Share Posted February 25, 2014 (edited) Welp, this post got really hijacked so... going to post a picture of my Intellivision System III The original black intv 2 style keypad was flaking apart, so I ordered these original style keypad replacements. Edited February 25, 2014 by ZarK Quote Link to comment Share on other sites More sharing options...
+JasonlikesINTV Posted February 26, 2014 Share Posted February 26, 2014 Wow, I just re-read the title of this post and had completely forgot what the original topic was. I thought they were building a sex robot 1 Quote Link to comment Share on other sites More sharing options...
jmetal88 Posted March 9, 2014 Author Share Posted March 9, 2014 I got a couple more games today! Night Stalker with box and one overlay, $3.99. Space Armada, complete, $1.99. Got 'em at Vintage Stock at the mall in Joplin. I've been to other Vintage Stock stores before, but this one is probably the largest. Massive selection! They didn't have very many 'rare' games like I've found at smaller stores before, but I guess that's probably because Vintage Stock is more well-known in the area and would probably sell the rare stuff more quickly than the smaller stores. Quote Link to comment Share on other sites More sharing options...
exodave Posted March 21, 2014 Share Posted March 21, 2014 Okay, this schematic is exactly the way I have mine built (not including the connections to the 3.5mm stereo jack). If I were to use a 1K trim pot in the place of R1, do I need to put terminal 1 to ground, or just hook terminal 3 towards +12V, and terminal 2 towards Video_In, and leave terminal 1 disconnected? Quote Link to comment Share on other sites More sharing options...
ZarK Posted March 27, 2014 Share Posted March 27, 2014 If I were to use a 1K trim pot in the place of R1, do I need to put terminal 1 to ground, or just hook terminal 3 towards +12V, and terminal 2 towards Video_In, and leave terminal 1 disconnected? When I used a trim pot, I left the extra terminal floating. Quote Link to comment Share on other sites More sharing options...
jmetal88 Posted June 19, 2014 Author Share Posted June 19, 2014 If I were to use a 1K trim pot in the place of R1, do I need to put terminal 1 to ground, or just hook terminal 3 towards +12V, and terminal 2 towards Video_In, and leave terminal 1 disconnected? I missed this post, I guess. Standard practice is to short the wiper terminal to one of the two ends to effectively turn it into a variable resistor. Which end you short to just depends on which direction you want to turn the knob. Feel free to get out a multimeter and experiment! Quote Link to comment Share on other sites More sharing options...
xefned Posted February 6, 2016 Share Posted February 6, 2016 Hey Jmetal, is the zener diode "shunt" circuit still required using your schematic? Or did you leave the RF modulator in place? I just wired it up following your schematic and I'm getting no picture. I'm thinking about trying the shunt circuit from the wiki. thanks, Matthew Quote Link to comment Share on other sites More sharing options...
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