jimblargh Posted February 11, 2022 Share Posted February 11, 2022 Hello friends! Does anyone know of an AV mod kit for the TRS-80 Coco 1? I am having a hard time tracking one down. I know some folks have done it without a kit, but at my skill level I feel much more comfortable using a kit. Background: I picked up a very nice Color Computer 1 yesterday, but upon connecting it to my TV I found that the RF output looks like garbage. I am not really picky about RF - most of my consoles are unmodified and I generally prefer it that way - but this looked bad. Kind of a moving reddish 'fog' over the green background with almost a flash every second or so. I cleaned the solder joints connected to the RF modulator as well as the plug-in itself but that did nothing. I tried a heavily shielded RF cable and saw no difference (not surprising- my consoles all do fine with this setup). I was able to make it look a lot better by adjusting the pots on the RF modulator, but I wasn't able to get it quite perfect. I suspect the modulator is going bad. I am aware of cocovga and I might go that route, but I want to make sure I am not missing an av mod kit that's out there. HDMI might also be a good output option if such a thing exists. Thanks for the help! Quote Link to comment Share on other sites More sharing options...
radventure Posted February 12, 2022 Share Posted February 12, 2022 I'm in a similar predicament. There's an excellent Modulator replacement (from 3rd party accounts), offered up by Ed Snider at TheZippsterZone Unfortunately it's out of stock for the variant I need and I've yet to hear back on availability. It feels like chip/tech shortage/price gouging, plus increasing demand on these very talented people, might be taking its toll. Quote Link to comment Share on other sites More sharing options...
R.Cade Posted February 12, 2022 Share Posted February 12, 2022 The CoCo 1 is pretty easy to mod with a couple of transistors. The CoCo 2 is a lot harder... 1 Quote Link to comment Share on other sites More sharing options...
radventure Posted February 12, 2022 Share Posted February 12, 2022 Ahh, apologies on that recommendation, I incorrectly assumed Coco1 and 2, it was just 2. 1 Quote Link to comment Share on other sites More sharing options...
ChildOfCv Posted February 12, 2022 Share Posted February 12, 2022 CoCo 1 uses one of those Astec RF modulator boxes. One solution, especially if you like to keep it original, might be to watch Ebay for a replacement box. Otherwise, the likely cause is that at least one of the tuning slugs is crumbling. They can be replaced by removing them from new tuning coils. Another common problem is broken solder joints on the output connector. Reflowing the connection inside of the metal box might fix things. The coaxial connector can also be a problem, but if you've tried other cables with the same result then you can probably write that problem off. 1 Quote Link to comment Share on other sites More sharing options...
tlindner Posted February 12, 2022 Share Posted February 12, 2022 I know this is not a pre built mod, but for the CoCo 1 it is on the very easy end of the difficulty level. http://www.cocopedia.com/wiki/index.php/CoCo-1_composite_video 1 Quote Link to comment Share on other sites More sharing options...
jimblargh Posted February 12, 2022 Author Share Posted February 12, 2022 17 hours ago, radventure said: Ahh, apologies on that recommendation, I incorrectly assumed Coco1 and 2, it was just 2. I saw that too. Thanks for the idea though! Quote Link to comment Share on other sites More sharing options...
jimblargh Posted February 12, 2022 Author Share Posted February 12, 2022 17 hours ago, ChildOfCv said: CoCo 1 uses one of those Astec RF modulator boxes. One solution, especially if you like to keep it original, might be to watch Ebay for a replacement box. Otherwise, the likely cause is that at least one of the tuning slugs is crumbling. They can be replaced by removing them from new tuning coils. Another common problem is broken solder joints on the output connector. Reflowing the connection inside of the metal box might fix things. The coaxial connector can also be a problem, but if you've tried other cables with the same result then you can probably write that problem off. Replacing the RF modulator is an interesting idea. I found this one on Ebay - do you think it might be swappable with the one in my CoCo? Quote Link to comment Share on other sites More sharing options...
jimblargh Posted February 12, 2022 Author Share Posted February 12, 2022 32 minutes ago, tlindner said: I know this is not a pre built mod, but for the CoCo 1 it is on the very easy end of the difficulty level. http://www.cocopedia.com/wiki/index.php/CoCo-1_composite_video Thank you for the resource! If I don't find any kit type options I might just try my hand at this. Quote Link to comment Share on other sites More sharing options...
ChildOfCv Posted February 13, 2022 Share Posted February 13, 2022 3 hours ago, jimblargh said: Replacing the RF modulator is an interesting idea. I found this one on Ebay - do you think it might be swappable with the one in my CoCo? Unfortunately I can't find anything on the UM1284, so I don't know. Astec makes a large number of modulators, and similar number does not guarantee compatibility. For instance, 1286 is a UHF modulator for PAL systems. 1285 is used in Intellivisions as well as CoCos though. If someone on the board has done an AV mod on theirs and still has the modulator, they may be willing to sell it. It's sad though, a while back when I checked ebay, there were a number of these modulators floating around. They seem to have dried up. 1 Quote Link to comment Share on other sites More sharing options...
jimblargh Posted February 13, 2022 Author Share Posted February 13, 2022 1 hour ago, ChildOfCv said: Unfortunately I can't find anything on the UM1284, so I don't know. Astec makes a large number of modulators, and similar number does not guarantee compatibility. For instance, 1286 is a UHF modulator for PAL systems. 1285 is used in Intellivisions as well as CoCos though. If someone on the board has done an AV mod on theirs and still has the modulator, they may be willing to sell it. It's sad though, a while back when I checked ebay, there were a number of these modulators floating around. They seem to have dried up. Good to know, thanks! I'll keep my eye out for a 1285 specifically, or maybe if I get a good deal on intellivision or coco 1 listed for parts. And heck, if nothing else I learned some things about RF modulators today! ? Quote Link to comment Share on other sites More sharing options...
MrDave Posted February 13, 2022 Share Posted February 13, 2022 Fyi.. replacing the rf module takes some good desoldering skills .. not the easiest thing to do. 1 Quote Link to comment Share on other sites More sharing options...
jimblargh Posted February 16, 2022 Author Share Posted February 16, 2022 On 2/12/2022 at 9:14 PM, MrDave said: Fyi.. replacing the rf module takes some good desoldering skills .. not the easiest thing to do. That too is good to know. To say that my soldering skills need practice is an understatement, so maybe I shouldn't get in over my head trying to desolder. Thank you! Quote Link to comment Share on other sites More sharing options...
MrDave Posted February 16, 2022 Share Posted February 16, 2022 Coco vga requires some mods but only 1 wire to solder. Very clear output..plus extra modes.. 1 Quote Link to comment Share on other sites More sharing options...
linville Posted February 28, 2022 Share Posted February 28, 2022 Sorry, late to the post...we need this added to a FAQ somewhere. For composite video on a CoCo1, be sure to check-out the tech segment on episode 34 of The CoCo Crew Podcast. It is quite easy to use a pre-assembled composite video amplifier circuit built for the Atari 2600 in parallel with the existing RF modulator -- very little soldering skill required, although a little skill with hand tools can be useful for mounting the RCA connectors! http://cococrew.org/ Quote Link to comment Share on other sites More sharing options...
jimblargh Posted February 28, 2022 Author Share Posted February 28, 2022 (edited) 2 hours ago, linville said: Sorry, late to the post...we need this added to a FAQ somewhere. For composite video on a CoCo1, be sure to check-out the tech segment on episode 34 of The CoCo Crew Podcast. It is quite easy to use a pre-assembled composite video amplifier circuit built for the Atari 2600 in parallel with the existing RF modulator -- very little soldering skill required, although a little skill with hand tools can be useful for mounting the RCA connectors! http://cococrew.org/ I just listened to the podcast and this is exactly the kind of fix that I am looking for! I only have one question - I see an option for an upgraded sound av mod for the 2600. Can I assume that this one would work the same on the coco, or would you stick with the more basic mod boards? Picture below for reference. Thanks a LOT!! Edited February 28, 2022 by jimblargh Typo Quote Link to comment Share on other sites More sharing options...
linville Posted March 14, 2022 Share Posted March 14, 2022 The sound option should work, so long as you tap the audio from the RF modulator as well. I think that most of them do not do any autio amplification, but they may add some filtering -- YMMV! Quote Link to comment Share on other sites More sharing options...
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