Atari A/V mod update
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Posted Mon Mar 2, 2009 3:59 PM
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I got my kit in the mail today and it's already soldered up waiting to be installed one of my 2600s tonight. For the most part it was a smooth assembly. The surface mount chip wasn't too hard to get into place. I did find the two .1uf caps next to that chip to be a little problematic -- they were wider than the space on the board, and I'm afraid of a short between the legs. The resistors weren't too bad; I first installed all the 75ohms, then used a multimeter to get the values of the rest and stuffed them in the board. I really like that you have the resistor values silk-screened instead of R numbers; it was much easier to match things up. The only other footprint issue was the 7804; it took some delicate work to avoid solder bridges.
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Posted Tue Mar 3, 2009 10:22 AM
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OK, I got the mod installed in my 2600 Jr, but I get no video. I suspect that a lead came off the TIA. Lifting the leads wasn't too bad, but I had some difficulty soldering the wires to the chip and probably need to redo those connections. Getting everything to fit inside the case was also a bit tough, snd the sticky tape just doesn't work to hold the board in place while you're working.
I verified that there were no bridges and that I had continuity from the TIA pins to the 4050. I also read 5V between the buffer's VCC and GND pins. At this time, I think I may have pulled a bad 2600 Jr... I made the mistake of not testing the console first. The main reason I suspect this is that the sound also wasn't working, and that's a totally different part of the circuit. Fortunately, I've got a few more Juniors, so I can pull a motherboard from one of them and reuse the case I already drilled. I'll be sure to verify the console works first before I start opening it up and soldering. |
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Posted Tue Mar 3, 2009 10:28 AM
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Posted Wed Mar 4, 2009 11:13 AM
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Posted Wed Mar 4, 2009 1:35 PM
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Posted Wed Mar 4, 2009 10:14 PM
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Success! Then failure.
I got everything soldered onto Junior #2. While opened up, I verified that S-Video and sound were working, and the picture looked quite nice. Then, while trying to get the board positioned, pin 9 of the TIA which I'd desoldered and lifted broke off the package, leaving me just a little thin strip of metal to try to connect. Grrr! The wires going to the TIA are pretty stiff. One thing that helped -- I opened the images from Longhorn's guide up in their own pages and used Firefox's zoom to make them larger. The default size on the guide page is a little small for me to easily follow. I'm going to try to get it reconnected, but so far my attempts have come loose almost immediately, so I may have to try some alternative method, like adding a second wire and then soldering to that. If I can't get this going, I guess I'll have to try console #3 |
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Posted Wed Mar 4, 2009 10:29 PM
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OK, a few more minutes of fiddling, and I think I've got an OK joint for now. However, I'm going to try to find my 4-switch or 6-switch and move the mod to there. No only does it have more room inside, it really would look nicer too to have all the ports on the back. However, I still get video out after putting the case back on, so I'm counting this a success.
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Posted Wed Mar 4, 2009 11:44 PM
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Posted Wed Mar 4, 2009 11:46 PM
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Posted Thu Mar 5, 2009 10:02 AM
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Posted Thu Mar 5, 2009 10:31 AM
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Posted Thu Mar 5, 2009 11:17 PM
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I'd also add a quick guide to soldering to pins. I've done a lot of through-hole soldering and some surface mount, but getting a good bond to a chip pin requires a few different techniques. What worked best for me was to tin the wire with extra solder, then hold the wire to the pin and apply heat to wire while pressing it against the pin. I had some problems initially with the stranded wire getting frayed when I was trying to work like I normally solder, where I apply solder to the joint after it's had a moment to heat.
I'd also include tips on using a multimeter to check for continuity to make sure there's no solder bridges between the pins. I ended up with one that I found before powering up my device that I was able to fix, but if I'd not done the check, I might have messed up the circuit. |
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Posted Fri Mar 6, 2009 8:45 AM
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I got my boards in the mail yesterday and put one together last night. I had to mount the resistors vertically, since the ones I have are too large to sit flush with the PCB - hopefully it will still fit inside the shielding. I hope to install it tonight. Once I have it done, I will be sure to share my results.
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Posted Fri Mar 6, 2009 12:25 PM
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Posted Fri Mar 6, 2009 2:26 PM
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Posted Fri Mar 6, 2009 2:39 PM
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Posted Fri Mar 6, 2009 2:45 PM
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Posted Fri Mar 6, 2009 5:18 PM
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Well A simple Decoder is all thats needed really. The SECAM version of the 7800 does this already. True - but my point was that you'd have to add active circuitry to convert the chroma/luma levels to RGB - thus defeating the purpose of RGB - the video isn't going to get any _better_ by converting it after it's been generated. -Ian Definitely! That's why we're interested in Longhorn's A/V mod. The act of modulating and demodulating the video signal is no longer necessary in the actual TV sets because A/V inputs are now a de facto standard and this process introduces unacceptable noise in the signal. Generating a RGB signal wouldn't improve noise ratio by any means. This mod is the best we cand do for the Atari 2600. I'm still waiting for my mod to arrive but I think it'll take longer to reach me here in southern Brazil. Congrats again! |
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Posted Fri Mar 6, 2009 5:39 PM
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Posted Fri Mar 6, 2009 6:48 PM
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Posted Fri Mar 6, 2009 8:43 PM
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