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retro486

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  1. I've got an Epyx Fast Load cart coming. Two actually, and an action replay I think (unlabeled red cart with two buttons).
  2. Anyone know if it might be either available as a kit or have the schematics and a parts list released if we want to save a few bucks/like to build kits? Personally I'd like to try an build the kit since it sounds like the new one will be simpler (no communication module) and I have a horribly under-utilized 3D printer...
  3. Alright, got my replacement 9901 and popped her in and that was it! The whole "enter" row is working as is the joystick "right" direction (well, working as well as it can with my super hacked up adapter that I made from the original completely broken joysticks). Sadly, I also got a MUCH nicer "spare" silver TI-99/4a today, so this project machine will be my new spare but I wanted to share that replacing the 9901 solved the original problem and for very little money. I got the replacement 9901 on ebay for $12 + $3 S&H in the US here: http://www.ebay.com/itm/Texas-TMS9901NL-Peripheral-Interface-Adapter-PIA-DIP40-/151579633037?roken=cUgayN&soutkn=oGUlAE. I got it in less than a week. The annoying part is desoldering the 40-pin from the board. If someone is going this route you ABSOLUTELY should solder in a socket. Hell, do that while you're waiting for your replacement like I did. Thanks everyone for all the help and narrowing down the issue! I learned a whole lot about this thing and greatly improved my soldering confidence.
  4. By horrible condition I mean they look like they were dredged up from the bottom of a muddy lake, so personally I'm not willing to risk it but true these things have been pretty reliable/repairable or I've been incredibly lucky. My 64k CoCo 2 had the power cord cut and it was a 2-second solder job to replace it and it powered right up with no other issues. The 16k had crayon all over it and looks like a kid was kicking it around the house like a soccer ball but it also works perfectly. I've had to replace chips on a TI-99/4a and a C64 breadbox which both were in cosmetically better condition than the CoCos, so I'd say of the computers I've purchased, the CoCo is the most durable... Shame it didn't have composite built-in but next month I'm planning on in touch with Ed Snider for the composite mod ( http://cocowares.com/item.php?nombre=CoCo2%20Composite%20and%20Sound%20board) if he's still making them... For the assembler I use the EDTASM+ cartridge with "TRS-80 Color Computer Assembly Language Programming" by William Barden Jr. I was using the PDF but I have a physical copy coming. So far I really enjoy it and I don't have a background in assembly or C/C++.
  5. Hah I was wondering why my joysticks "right" signal was unresponsive and there you go. looking at p11 of the 4a doc I see the enter row and joystick right share an interrupt on pin 7 of the 9901. I'm no expert but that's a strong implication the 9901 is indeed at fault, right?
  6. Dang. Well I have a replacement chip on the way and I already added a socket so at least the tedious bit is already done. I'll update here if it works. Hopefully my socket work isn't garbage!
  7. Black on 1, red on the rest. They're all negative when I did it that way though I suppose if I put red on 1 they would be positive. The enter key doesn't work either, unfortunately. I saw pun 1 leads to the joystick port down the line so I tried desoldering the joystick port but it was no help. I'll take a look at the pin 12 path since the rest seem fine. I've been fixing solder as I find rot/air bubbles. This is the most I've soldered in my life so getting a lot of experience! Including to pay attention to how I'm holding the iron, as this lovely small burn on my palm will show.
  8. Enter (12) is almost 3.5v. The rest are 0.12-0.15v...
  9. Ok I was just checking continuity, I wasn't checking voltage. Thanks for the instructions, I did a voltage test and all keys show some voltage then drop to 0 once I press them. So I guess there's no short?
  10. With the keyboard removed, there's no issue. Continuity test beeps only when I press the keys. Now on the keyboard header on the motherboard, with power off all the pins appear disconnected (no continuity). Once I apply power, pins 1 and 12 (sorry I miscounted) short. A few others short with 12 as well: 6, 7, 8, 9. I do have a spare ti99/4a coming late next week that I can test with but I'm impatient.
  11. Ok. I socketed the 9901 but I haven't replaced it yet (still the original 9901), resoldered the keyboard cable and the keyboard pins on the motherboard. With no power, continuity checks out. Once I apply power, pins 1 and 13 short. These are the two that my dead keys use. All other keys work perfectly. That should narrow it down but I have no clue what that means... a short in a gate that's only closed when powered on?
  12. Nope. Resoldered the keyboard cable connector both on the keyboard and on the motherboard, also resoldered each point in the failing chain on the keyboard with no improvement. I removed and reseated all chips that could be reseating also with no improvement. I've ordered another TI-99/4a and this one will be my parts machine. It'll also let me test if the keyboard is any good. Thanks for the help everyone!
  13. Alright well I removed them and restored the original chips and after a lot of tweaking finally got video in BW then more tweaking and I got color back! Fixed the floppy drive too (multiple issues). If anyone wants these bits (the fast loader parts, not the floppy drive) or would trade for a NTSC games floppy or two I'd be up for it... Again, I don't have the special cartridge these connect to...
  14. From what I can tell the CoCo 3 is highly sought after as it has increased memory, graphics, and sound capabilities. Also could run double speed, I think... Still no sprite support but it was the last of the official CoCo line. There's a lot of work making a kind of "CoCo 4" out of FPGA boards as well. I think one of the kits (well, it was a prefilled shopping cart) ran around $160 for the parts... How to Build a “CoCo 4” – cococommunity.net Been trying to source a reasonably priced CoCo 3 myself and not having much luck. Mostly the ones that pop-up on ebay that are in my price range are in horrible "untested" condition. In the meantime I have two CoCo 2's, a 16k and a 64k which I've been using to learn assembly on.
  15. Hi! It looks like this is the master thread for ebay tip offs so might get more visibility: http://atariage.com/forums/topic/215689-ti-related-ebay-heads-up-notice/
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