Jump to content


  • Content Count

  • Joined

  • Last visited

Community Reputation

16 Good

About ckrtech

  • Rank
    Chopper Commander

Profile Information

  • Gender

Recent Profile Visitors

13,747 profile views
  1. Wow. That's wild. I look forward to your updated document. I am wondering about "re-clocking" the TIA chroma on an NTSC Atari 7800 to see what effect it has on 2600 chroma output. The MARIA outputs the TIA CLK line to the TIA chip (by way of a 100 ohm resistor) on the NTSC console. Perhaps it is possible to clean-up color backgrounds among other things for 2600 games on an NTSC 7800.
  2. @juansolo Would you mind summarizing your discoveries, benefits, and overall knowledge about the chroma component of the 7800 - your intentional switching of the TIA/Maria color, your relay circuit, and the benefits gained? I read over the thread recently, but hindsight makes it easier to collect one's thoughts - provided you have the time for it, of course.
  3. Empire works fine. Battlezone has a few issues.
  4. Is there a full list of games with odd video timings? I just got my 5X-Pro today. I imagine I will run it through a gauntlet of consoles this evening. I can try a few things out. I have Empire and Battlezone. No Starmaster, though.
  5. Is that typical for combining chroma and luma for PAL? No other components needed? As far as the UAV, I feel that it is the current go-to board for the 7800, but yeah - it is far from perfect. I tried messing around with the TIA signal I fed the UAV (using a few other passive components) just for a bit. Nothing of note really changed. I was also unable to duplicate the scope signal I shared earlier, but I may have also had MARIA chroma disconnected from the UAV this most recent time. I moved TIA chroma from the tcol input to the main color input just to see if a circuit change would make a difference, but it didn't. Great work on your latest AJM revision, btw. I hope you get a chance to mess around with an NTSC console as well.
  6. juansolo, I don't want to hijack your thread as I am diverging from your thread title as this is an NTSC system. I can always split this off and start a new thread if you prefer. I did move the ground wire as @-^CrossBow^- suggested. It is super short and connects to one of the holes where the RF modulator was. No change in the jailbars on the 2600 side. I disconnected the MARIA col input from the UAV and lifted resistor R17 to disconnect the TIA color from the chroma tying circuit. No change. Of course, pressing the "Pause" button to disable color results in an image without jailbars. I put the wire back, put R17 back in place and scoped the UAV's composite output (yellow) as well as the stock 7800 composite feed that normally goes to the RF modulator (cyan) - with the probe clipped on the RF modulator side of C8. I managed to single-shot a line of video with the trunks of the trees in Pitfall (I took a photo of the CRT image and lined the trees up in the image below for kicks). What is interesting about the two signals (both lack 75 ohm termination as I disconnected the AV cable from the CRT so they would be the same) is that the UAV output of the 7800's 2600 signal (yellow) is kinda "lazy." Compare it to the stock 7800 composite that is fed to the RF modulator (cyan signal), and you can see how much sharper the pulses are - how they ramp up/down versus the UAV output. The amplitude's peak-to-peak level from the UAV (yellow) between the trees shouldn't vary like that. It should be even peak-to-peak - swinging around the desired luma level all the way across just like the stock 7800 signal (cyan). It should be the same, solid color, the same luma level, the same Hue, and the same saturation.
  7. 22 awg stranded. UAV is where RF modulator used to be. Grounding wire is a bit long as it runs to the center-right rail (i will most likely change that...) All other wires are short. I do plan on replacing the 7805 - in fact, I have some spares around here somewhere. I only composite + composite ground hooked up to the output pads at the moment. No s-video. The jailbars are definitely present on the 2600 side. I see the benefit of switching between the two chroma circuits, but I also wonder if the chroma<->luma relationship is a bit out of spec even with the UAV in place. Specifically that the chroma amplitude is too high relative to the luma's signal.
  8. I would have definitely left the RF modulator in there, but it had stopped functioning properly. I created a breadboard-based transistor mod just to verify the console was working and then elected to put the UAV mod in for something a bit more in-spec. I certainly don't mind building the switching board for the chroma circuit and even poking the chroma lines with my oscilloscope just a little bit. Unfortunately, I do not have a flash cart or a test cart at the moment.
  9. I had an extra UAV sitting around that I put in an NTSC Atari 7800 the other day. The 7800 games that I have tested so far look pretty good, but of course I tried the 2600 side with Pitfall and had jailbars everywhere. The RF modulator was removed prior to the install, and now I am considering pulling/lifting R16 and R17 to separate them from the leftover combination circuit and using the chroma switcher with the CD4053 from the AJM 2.2 PDF. Were there any other tweaks you thought about trying to clean up the signal (I saw the photo of the LCD with the jailbars a few pages back)? I am also curious if anyone else has done this mod on an NTSC 7800.
  10. Ahh cool. I certainly wish you the best of luck with your 1702 situation, griff3125. I own a 1702 and recapped it a few years back with a kit from console5.com. As a fan of IBM and compatibles, I am also rather interested in your little RGBI mod you have there since it seems like that is what it is. It would be nice if there was some sort of documentation on it - the circuit Digitek used for both the board, their solder points, and the components they changed/added/removed on the board itself.
  11. I am interested in any other photos you might take of the mod before you rip it out.
  12. I am doing maintenance on a Radica Space Invaders Atari 7800 controller, and it looks like the manufacturer glued the hex screw into the bottom of the shaft of the joystick. Attempting to remove the joystick from the housing resulted in the screw snapping in half - a very clean break. I was wondering if any of you that made a 7800 controller out of the RSI made any modifications to the joystick or replaced it. To restore the original, I am most likely going to have to drill out the screw remains from each side and find something with the correct thread size. Alternatively, I could go for an entire shaft replacement that is compatible. Weighing my options now, but I am wondering if any of you RSI 7800 controller users have any experience to share - be they repairs or even if you found a full replacement stick assembly of appropriate size and managed to mount it in the RSI housing.
  13. I picked up a Heavy that needs some work. I opened it up and there are no pads on the difficulty switches. Seems like a safe assumption that someone else was in here at some point, but I thought I would ask if this is potentially normal for some of the units.
  14. Hey guys - I just picked up Reactor. The cartridge door openers are very stiff - enough so that the cart won't sit in the slot on the Atari - it just springs right out of the slot. I would really like to refrain from poking a hole in this cart's label and opening it up in order to take a look at the problem. Anyone have a fix suggestion?
  • Create New...