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XEGS: Mission Impossible: no drilling/keep shielding/no bolts


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Maybe you've noticed my sporadic struggle with my randomly acquired XEGS. After fixing all the hardware issues, receiving the Ultimate 1MB, Stereo and U-Switch and reading heaps of AA posts (thanks guys, esp. mytekcontrols' posts I have saved with pictures and comments :)) I gave it some thought.


For some reason I really liked the idea of replacing the RF modulator with Composite output and reuse the unused cinches for L/R (it seems nobody has done anything like that before?). And while doing that, I was trying to figure out what to do with the U1MB PCB as I had no intention of drilling holes anywhere. And then it hit me -- maybe I can use either the empty Composite/Audio connector holes for the bolt or even better, maybe I can use the RF modulator case as a mounting surface?


I already had stereo installed, so after removal of the modulator and rearranging the outputs this is what I had in the beginning:




After hours of experiments and gymnastics with the flat cables I was nearly sure I want to follow the path of using the free Composite connector's hole right to the modulator case and put the U1MB board on the modulator. But then I realised I can't use the pins and shielding together plus I'd need to remove the modulator case as well (actually it was possible to have screw+bolt and the modulator but the screw wasn't 100% orthogonal to the PCB and it didn't feel right -- U1MB's components were touching the metal, one stronger push could damage them). And then I realised that the U-Switch actually doesn't fit with the cartridge case. That was it, there must be a better solution.


What about the other idea, using the modulator's case as the base for everything? Accidentally I realised that the U1MB's pins on the other side of the PCB have isolated bottoms with tiny little space which happens to be the exact thickness as the modulator's wall. And as bonus, the other side is much friendlier to the modulator's case, no ICs or resistors touching anything, everything fits nicely and most importantly, holds without any screws!


So let's isolate the walls, just to be on the safe side:




Attach the board, add six wires (argh...) to move the U-Switch, wire everything up:




... will it work?




I didn't realise there's a LED on U-Switch so now I have a shining cable :D


Final touch with transparent tape to make the flat cables stick on each other:




But will it really fit?




It does!


And the top case covers every imperfection:




Is it really worth it? Hard to say, the shielding definitely isn't something you need, same for the cartridge case. I was just curious to try it out. I use this XEGS as a training field for my Falcon (heresy!!!) as I'm still just learning how to properly solder and desolder ICs, wires, IC legs (horror!), ...


Don't try this at home! ;-)

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Nice job cramming all of that in there underneath the shield no less. Quite impressive.


Yep the only way I got the U-Switch/Stereo combo to work in my XEGS was by filing off the corner of the U-Switch where it overlaps the Cartridge Guide. Although I had to file so much off that I then had to patch a trace that disappeared in the process. Life became so much easier when I decided to create a replacement for the Stereo, U-Switch, and TK-II in the form of the TK-II-Stereo board.


Now you just need to update the U1MB bios with FJC's alternative, and you'll have a kick ass system for sure :grin:


- Michael

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There's one more thing even more urgent -- I need to buy 2xRCA -> 3.5mm female converter before everything else because now I can't listen to the hard earned stereo at all, I had to test it separately for each channel. :D


But yep, the 'alt' firmware seems like the way to go, I'm impressed especially by the amount of detail in documentation, loved i!

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  • 4 years later...

Nearly exactly five years to the dot, I can update my original post. A year ago I had an issue with ROM and instead of diagnosing it by myself I let someone else do it. The trouble was that the fix was just temporary and he tampered with my original wiring so I couldn't close the XEGS anymore:




So when a few days ago the problem reappeared I decided to fix all the problems (in the end it was a badly soldered ROM socket, my soldering skills weren't great back then). I noticed that the U1MB pins can be actually grouped with an IDC header:




That allowed me to create much cleaner wiring (as you can see, I also replaced the horrible thick red wires with classic audio ones):




I intentionally kept the unused wires from the ribbon cable there so future expansions could be added to it (doubtful but perhaps COVOX would one of them).


Assembled together all works nicely, even the cartridge port works after the cleanup now:





Edited by mikro
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