Musicdad Posted November 4, 2021 Share Posted November 4, 2021 How about doing a SMC version. This would clear upnALOT of space for built in upgrades on board. I am little excited to try your new board. When will you have Gerber files available? 1 Quote Link to comment Share on other sites More sharing options...
Tornadoboy Posted December 31, 2021 Share Posted December 31, 2021 Just thought I'd give this a nudge and see if there's anything new going on? Hope all is well over there? I've been playing around with Sprint Layout a lot lately and making gerbers of some rare arcade related stuff and I'm starting to get tempted to do one of the motherboard and make some mods of my own, mainly just making the board in two sections so it'll fit in smaller cases and maybe changing some of the connectors, though I don't know if I'm up to the task of incorporating upgrades like internal 32k and such. Is there a gerber for the original motherboard available anywhere? Quote Link to comment Share on other sites More sharing options...
rkrenicki Posted February 18, 2022 Author Share Posted February 18, 2022 (edited) On 11/4/2021 at 7:06 AM, Musicdad said: How about doing a SMC version. This would clear upnALOT of space for built in upgrades on board. I am little excited to try your new board. When will you have Gerber files available? I am still needing to sort out the DIP version.. baby steps So, I finally found a bit of time in that magical center of the Venn Diagram of (Space on my workbench) and (Motivation to work on the TI) this morning. It looks like there is an issue in the system GROM area, as GREADY is constantly being pulled low. The GROMs themselves work fine in another system and the 74LS04 inverter chip tests fine, but I did swap it for good measure with no change. I ended up getting called into work at this point, but diagnostic progress has been made. I need to dig out my other power supply so I can power both the good original PCB and the non-working new PCB at the same time and do some proper side-by-side measurements. I am thinking about cleaning up and publishing the schematic portion of the KiCAD project up on my Github, so that I can get some more eyeballs on it. I am thinking I am just missing something really small here. Since the PCB layout is not working, I will not publish that part quite yet. Edited February 18, 2022 by rkrenicki 3 Quote Link to comment Share on other sites More sharing options...
rkrenicki Posted February 18, 2022 Author Share Posted February 18, 2022 I did stick the schematics and the base project file up on my Github here: https://github.com/rkrenicki/TI99-Motherboard It is in KiCAD 6.0 format, so you will need to be on at least that version to open it. The layout has not been cleaned up.. about half of the hierarchical sheets are going to go away in the end, but I wanted to focus on getting the errors figured out before fixing the layout. If anyone wants to peruse the schematics and sees anything amiss, let me know! 4 Quote Link to comment Share on other sites More sharing options...
LouisB Posted February 19, 2022 Share Posted February 19, 2022 17 hours ago, rkrenicki said: If anyone wants to peruse the schematics and sees anything amiss, let me know! Hi rkrenicki I took you up on your request to peruse the schematics. I compared them against the MainByte Copy of the TI-99/4A Console Technical Data: CPU - looks good Address Decoding - looks good 8/16 Bit Switch - looks good ROM / RAM / Sound - looks good Power - didn’t check GROM Logic - Looks good Video - checked it over some, looks good although I skimmed some of the power feed Keyboard - didn’t check GROM IO Port - checked a little bit of this, it’s spread out on the schematics a trickier to validate than the others Tiny thing on the 8/16 Bit Switch, U615 is missing a bypass capacitor on VCC. I'm more or less putting this here to convince you I actually did look at the schematics ? Also a question, I noticed this arrow on the main byte schematics, south of the grom's and east of the memory address decode. Probably just a trivial artifact. Wonder why that cute little arrow is there ? I’m still a newcomer, but my eyeballs agree with you that the schematics look pretty solid, and I'm still a little nervous because fabrice has stated outright that there are lots of errors in the official documentation, so I assume you will have to work through those, and I'm wondering how many of the "errors" are small things like component values, and how many are larger leaps like whole components and /or connections wrong or missing! Good luck and god speed, if you have any other specific areas you would like eyeballs on please let us know. 3 Quote Link to comment Share on other sites More sharing options...
rkrenicki Posted February 19, 2022 Author Share Posted February 19, 2022 (edited) U615 does not have its "own" bypass cap on the original documents, however C608 (0.1uF), C601 (1nF), and C609 (0.1uF) are right there between the CPU and U614-616, acting as bypass capacitors for all of those chips. These are all powered by the flood-fill on an inner layer, so they are all bussed together. . I am not entirely sure of the significance of the Arrow there either. As for the Power sheet, you will note that I have removed a bunch of ferrites and coils from the power input. I did try both with and without those extra filters and I found no significant difference on power delivery, so I chose to omit them. I am not nearly as afraid of EMI compliance as TI was back in the day. The Video sheet will look a little different as well since I tried to incorporate both NTSC and PAL options. As for the rest, I did catch a few errors. It was about a year ago since I was working them, but an incorrect voltage reference comes to mind, a couple of value issues as well, but nothing too out of the ordinary. Edited February 19, 2022 by rkrenicki 6 Quote Link to comment Share on other sites More sharing options...
+Ksarul Posted December 8, 2022 Share Posted December 8, 2022 @rkrenicki, have you been ale to take this project any farther? So far, it looks interesting. . . 1 Quote Link to comment Share on other sites More sharing options...
LouisB Posted December 8, 2022 Share Posted December 8, 2022 BTW @Ksarul there's a project in progress here: TI/99 4a clone | Vintage Computer Federation Forums Not a drop-in replacement, but clone. 4 Quote Link to comment Share on other sites More sharing options...
rkrenicki Posted December 9, 2022 Author Share Posted December 9, 2022 My day job has been taking up a lot of my time as of late, and I have not really had much of an opportunity to dedicate back to this. That said, Thanks for the link to the clone project! I can compare my schematics to that and see where my mistake is. 4 Quote Link to comment Share on other sites More sharing options...
+dhe Posted September 30, 2023 Share Posted September 30, 2023 @rkrenicki hi, it's been not quite a year, since your last posting. Does time and interest look any more plentiful in the coming year? 1 Quote Link to comment Share on other sites More sharing options...
RickyDean Posted October 31, 2023 Share Posted October 31, 2023 (edited) @rkenicki , would you be willing to share your symbol library for the TMS9901 chip? I'm trying to create a schematic for a Corcomp style FDC on Kicad. Thanks, regardless. Never mind I found your github work. Thanks Edited October 31, 2023 by RickyDean Quote Link to comment Share on other sites More sharing options...
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