+remowilliams Posted June 10, 2018 Share Posted June 10, 2018 Has anyone else swapped out the dual 7805s in the 1200XL with the newer DC/DC converters? I've replaced both of them in my main 1200XL today with the Traco TSR 1-2450s and the heat difference is astonishing. That massive chunk of steel in the corner (and the case itself) is barely registering any heat now... 7 Quote Link to comment Share on other sites More sharing options...
Gunstar Posted June 10, 2018 Share Posted June 10, 2018 (edited) I hadn't thought of doing it myself, but now that you mention it, maybe I can forgo the fan I was going to install and replace the 7805's too. I decided a while ago not to do the straight +5V power conversion, because I like the extra amperage for upgrades I get with my 3+ amp Atari universal PSU I use. Edited June 10, 2018 by Gunstar Quote Link to comment Share on other sites More sharing options...
flashjazzcat Posted June 10, 2018 Share Posted June 10, 2018 Could you not just do the 5V mod and use a 3A 5V DC PSU? That's what I did. The wiring isn't too pretty on the underneath, though. Reno's mod sounds pretty good, anyway. Quote Link to comment Share on other sites More sharing options...
Gunstar Posted June 10, 2018 Share Posted June 10, 2018 (edited) Could you not just do the 5V mod and use a 3A 5V DC PSU? That's what I did. The wiring isn't too pretty on the underneath, though. Reno's mod sounds pretty good, anyway. Yes, I could i suppose, I hadn't really looked further than 5V PSU's I have on hand that have half that amperage or less. It's also a case of "if it ain't broke, why fix it." I'm not all that concerned of conserving a bit of energy in this situation and my current PSU has the amperage I need. as far as heat concerns due to the original power supply and circuit, I was going to install a fan and some IC heat-sinks like I saw done in a C64 rebuild video, but I don't mind changing a couple of 7805's out if that alone makes it all much cooler. But for me it's also some of my upgrades, I've noticed that the GAL chips get pretty damn hot, and I'd like to extend their life, so a fan may still be needed. Right now I made some home-made heat sinks out of aluminum foil and lithium grease for the GAL's. I've got too many other half or near finished projects already, too, so anything like a PSU change is way down the list at this point. Un-pretty wiring is already a fact with my 1200XL with the PBI mod and other "fixes" I've done to make it more 800XL compatible, so too late for me on that point. Edited June 10, 2018 by Gunstar 1 Quote Link to comment Share on other sites More sharing options...
Faicuai Posted June 10, 2018 Share Posted June 10, 2018 Has anyone else swapped out the dual 7805s in the 1200XL with the newer DC/DC converters? I've replaced both of them in my main 1200XL today with the Traco TSR 1-2450s and the heat difference is astonishing. That massive chunk of steel in the corner (and the case itself) is barely registering any heat now... Considering the inherited similarities between the 1200XL and 800 power-supply stages, this could also work wonderfully for the 800... where MULTIPLE levels of DC-voltage need to be generated right of its power-board, IIRC. 1 Quote Link to comment Share on other sites More sharing options...
flashjazzcat Posted June 10, 2018 Share Posted June 10, 2018 It's also a case of "if it ain't broke, why fix it." Precisely the question that caused me to wonder why you would want to install active cooling in an Atari 8-bit computer. Quote Link to comment Share on other sites More sharing options...
Gunstar Posted June 10, 2018 Share Posted June 10, 2018 (edited) Precisely the question that caused me to wonder why you would want to install active cooling in an Atari 8-bit computer. Because I want to keep them unbroken? That theory, for me, only includes what I see fit, with the choice to ignore it if I feel like modding or upgrading. But a stock 1200XL also has a lot of things that are generally considered "broken" to start with, the usual +5V SIO fix, keyboard membrane fix, S-video line fix, etc. and those fix's fall under the "It's broken, fix it" catagory, including the lack of a PBI. It's easier to add a little fan and change a couple 7805's than doing a full power circuit hack too, considering the rectifier removal...so the bottom line is I decide where I want to be lazy or not and it's all justification and excuses. Edited June 10, 2018 by Gunstar Quote Link to comment Share on other sites More sharing options...
flashjazzcat Posted June 10, 2018 Share Posted June 10, 2018 Well, the need for an enormous heatsink and bridge rectifier to make 9VAC usable on a machine which internally runs entirely off 5V DC might seem like something worth fixing if one is inclined to aim critical thinking at the 1200XL, especially when one intends to fit a PBI connector. The only time I affixed to a fan to the CPU of an A8 was to address something which actually did break when it got warm, but that was a rather extreme situation and it all seems quite ridiculous in hindsight. Quote Link to comment Share on other sites More sharing options...
Mathy Posted June 10, 2018 Share Posted June 10, 2018 Hello Jon IIRC the 1200XL needs 12V for the video circuit. Sincerely Mathy Quote Link to comment Share on other sites More sharing options...
flashjazzcat Posted June 10, 2018 Share Posted June 10, 2018 IIRC the 1200XL needs 12V for the video circuit. It does? I must be hallucinating the video output on my 5V DC machine, then. 1 Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted June 10, 2018 Share Posted June 10, 2018 Hello Jon IIRC the 1200XL needs 12V for the video circuit. Sincerely Mathy No, it surely doesn't. The only thing the 12V rail coming off the rectifier does is feed the voltage regulators and the 12V pin on the SIO port (a signal dropped from later XL/XE machines). 1 Quote Link to comment Share on other sites More sharing options...
flashjazzcat Posted June 10, 2018 Share Posted June 10, 2018 The only thing the 12V rail coming off the rectifier does is feed the voltage regulators and the 12V pin on the SIO port (a signal dropped from later XL/XE machines). I was sufficiently interested in the folklore of the 12V pin of the 1200XL SIO connector to haul a stock machine out of the cupboard just now and measure it. There isn't even a trace connected to SIO pin 12, although I guess one could add it as an aftermarket modification. But there's nothing there out of the factory. Correct regarding the regulators, though. 1 Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted June 10, 2018 Share Posted June 10, 2018 I was sufficiently interested in the folklore of the 12V pin of the 1200XL SIO connector to haul a stock machine out of the cupboard just now and measure it. There isn't even a trace connected to SIO pin 12, although I guess one could add it as an aftermarket modification. But there's nothing there out of the factory. Correct regarding the regulators, though. That's what I get for relying on a quick Google. I *thought* I had read years ago that the 12V SIO line from the 400/800 was deleted in the 1200XL and later models, but Googling the pinout said otherwise. So much misinformation on the web. Quote Link to comment Share on other sites More sharing options...
flashjazzcat Posted June 10, 2018 Share Posted June 10, 2018 Yeah: for once the schematic tells the truth. 1 Quote Link to comment Share on other sites More sharing options...
Level42 Posted June 10, 2018 Share Posted June 10, 2018 I'm still curious if those high frequency switching converters will last as long as the original 7805's did. Only time will tell, but if they fail, they will take out parts on your machine......not with 7805's.....I've never seen one die "aggressively"....only "peacefully" (which means the output got LOWER than the specced voltage instead of higher). 2 Quote Link to comment Share on other sites More sharing options...
Osgeld Posted June 10, 2018 Share Posted June 10, 2018 (edited) yea drop ac into a 7805, I was making a clock and not paying attention and it was getting ~9VAC, which passed right though it presenting 9VAC (with a stunted waveform) directly to all my logic chips (and of course the 7805 was just acting as a heater from that point on) 7805 is tough but not impossible Edited June 10, 2018 by Osgeld Quote Link to comment Share on other sites More sharing options...
flashjazzcat Posted June 10, 2018 Share Posted June 10, 2018 So: if it ain't broke... Quote Link to comment Share on other sites More sharing options...
+remowilliams Posted June 10, 2018 Author Share Posted June 10, 2018 Only time will tell, but if they fail, they will take out parts on your machine......not with 7805's.....I've never seen one die "aggressively"....only "peacefully" (which means the output got LOWER than the specced voltage instead of higher). I'm not worried about 'catastrophic' failure, they seem well made. Also: (Reliability, calculated MTBF (MIL-HDBK-217F, at +25°C, ground benign) >5’350’000 h) I've left it on since I did the swap, you can still just barely tell the machine is on. I'm calling this one a victory so far, for a few minutes work 2 Quote Link to comment Share on other sites More sharing options...
Mathy Posted June 10, 2018 Share Posted June 10, 2018 Hello guys Hmm, must have been the 400/800 that used 12V for video and that one SIO pin... Sincerely Mathy Quote Link to comment Share on other sites More sharing options...
Osgeld Posted June 10, 2018 Share Posted June 10, 2018 I know the 400 used it for ram Quote Link to comment Share on other sites More sharing options...
Fox-1 / mnx Posted June 10, 2018 Share Posted June 10, 2018 I'm lazy so I'll ask... What's the frequency of those Traco stabilizers? Are they suitable for analog audio equipment without having to worry about audible side effect? Quote Link to comment Share on other sites More sharing options...
Osgeld Posted June 10, 2018 Share Posted June 10, 2018 I don't recall, they are not a magic bullet though and do put out noise since its a low cost switch mode power supply in a compact package if you notice it or not is dependent on many factors of the target machine (like they cause all kinds of crap on some game systems, but nothing at all on others due to placement on the board and trace layout) Quote Link to comment Share on other sites More sharing options...
+remowilliams Posted June 10, 2018 Author Share Posted June 10, 2018 What's the frequency of those Traco stabilizers? Are they suitable for analog audio equipment without having to worry about audible side effect? From the datasheet: Switching frequency 500 kHz ±10 % (pulse width modulation) if you notice it or not is dependent on many factors of the target machine (like they cause all kinds of crap on some game systems, but nothing at all on others due to placement on the board and trace layout) Yes, board layout and component placement seems key as to whether you might get side effects or not - which is why this was somewhat of an experiment after replacing the 7805 in my 7800. Quote Link to comment Share on other sites More sharing options...
+Nezgar Posted June 11, 2018 Share Posted June 11, 2018 (edited) Hello Jon IIRC the 1200XL needs 12V for the video circuit. Sincerely Mathy I recalled this old post mentioning how the need for >5VDC was satisfied in the XL's http://atariage.com/forums/topic/155245-vertical-lines-on-many-xe-computers/?p=1918358 The CADJ pin is a DC input that varies the phase delay of the CHROMA signal. As you adjust CADJ, the color of the pixels change. The 400/800 had +12v available from their power supplies which was used to feed the adjusting pot. The XLs and XEs do not have +12v so they used a voltage doubler circuit to feed the their pots. But, it is a DC voltage. You can actually lift the CADJ pin and feed it with a signal to change the color dynamically, if you want. If you want a "brighter" screen, increase the value of the output resistor of the driver circuit. Edited June 11, 2018 by Nezgar 2 Quote Link to comment Share on other sites More sharing options...
+Nezgar Posted June 11, 2018 Share Posted June 11, 2018 (edited) And another recent thread discussing using these switching regulators in a 1050 - which uses both 5V and 12V http://atariage.com/forums/topic/274483-the-greener-1050/ Edited June 11, 2018 by Nezgar 1 Quote Link to comment Share on other sites More sharing options...
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