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JJB

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About JJB

  • Rank
    Space Invader
  • Birthday 03/12/1968

Profile Information

  • Gender
    Male
  • Location
    Wellington, New Zealand
  • Interests
    Pretty much everything electronic & mechanical; returning to the TI99/4a after 25 years
  • Currently Playing
    with FinalGROM99
  • Playing Next
    with DSK emulation on the cheap

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  1. Apologies have to revise my story about AC-coupling the R-G-B signals, it did cause colour smearing in some cases. Fine-tuning the capacitor values would probably solve that but I decided to remove the electrolytics and live with a bit of colour diff; picture quality is still great. I had a problem with noise on the TMS-RGB sync line, causing my RGB->HDMI converter to re-sync and show that annoying OSD. Chased a lot of red herrings but can only conclude the noise is generated by TMS-RGB. With a scope and a capacitor decade box I determined that a 10nF capacitor between sync and ground nicely cleans up the signal and makes the converter behave. Hope that helps, Jochen
  2. See attached pic; the 2.2uH in parallel must mean I ran out of 1uH 🙂 Values are based on testing with various inductors, a capacitor decade box and a scope. Low ESR turned out to be essential.
  3. I does depend on the DC-DC converters you're using I suppose; after my TI power board decided to quit I adapted it to use those cheap Ebay LM2596 modules (the ones you can adjust with a 10 turn pot) for +12V and +5V and some other type (have to check) for -5V. All had quite a bit of ripple to it (>200mV from memory) so I added an inductor and a low ESR elco to each output. Now the ripple is within 50mV for all of them and the TI seems to be happy (don't have a F18A though). The +5V gets to ~40C with a small custom heatsink, +12V and -5V stay cool; better still the TI stays quite a bit cooler too!
  4. this one? http://www.mainbyte.com/ti99/hardware/peb/avpc.html
  5. Just confirming that TMS RGB works very well in my US TI after replacing the TMS9918A with a TMS9928A I purchased from Ebay. Pin 38 (CPUCLK) wasn't used for the sound processor so I just terminated it with a 560R resistor, same with pin 35 (EXTVDP). The composite video signal from pin 36 goes to a inductor (L202) first, I cut the incoming side and bent it out of the way. Right under that inductor is an unused wire link which can be conveniently used to terminate pin 36 with another 560R resistor. I re-used the existing TI video connector to provide RGB out and made a custom DIN - SCART cable to connect to a cheap RGB - HDMI converter. SCART needs a positive potential on pin 16 (Fast Switching) to select RGB instead of CVIDEO but with a 5-pin DIN I didn't have a spare pin to carry 5V from the console. I just opened up the converter and connected pin 16 internally to a suitable 5V point via a current-limiting resistor. Cheers, Jochen
  6. Just confirming that TMS RGB works very well in my US TI after replacing the TMS9918A with a TMS9928A I purchased from Ebay. Pin 38 (CPUCLK) wasn't used for the sound processor so I just terminated it with a 560R resistor, same with pin 35 (EXTVDP). The composite video signal from pin 36 goes to a inductor (L202) first, I cut the incoming side and bent it out of the way. Right under that inductor is an unused wire link which can be conveniently used to terminate pin 36 with another 560R resistor. I re-used the existing TI video connector to provide RGB out and made a custom DIN - SCART cable to connect to a cheap RGB - HDMI converter. SCART needs a positive potential on pin 16 (Fast Switching) to select RGB instead of CVIDEO but with a 5-pin DIN I didn't have a spare pin to carry 5V from the console. I just opened up the converter and connected pin 16 internally to a suitable 5V point via a current-limiting resistor. Cheers, Jochen
  7. Just confirming that TMS RGB works very well in my US TI after replacing the TMS9918A with a TMS9928A I purchased from Ebay. Pin 38 (CPUCLK) wasn't used for the sound processor so I just terminated it with a 560R resistor, same with pin 35 (EXTVDP). The composite video signal from pin 36 goes to a inductor (L202) first, I cut the incoming side and bent it out of the way. Right under that inductor is an unused wire link which can be conveniently used to terminate pin 36 with another 560R resistor. I re-used the existing TI video connector to provide RGB out and made a custom DIN - SCART cable to connect to a cheap RGB - HDMI converter. SCART needs a positive potential on pin 16 (Fast Switching) to select RGB instead of CVIDEO but with a 5-pin DIN I didn't have a spare pin to carry 5V from the console. I just opened up the converter and connected pin 16 internally to a suitable 5V point via a current-limiting resistor. Cheers, Jochen
  8. Using Tursi's schematic (thanks Tursi, didn't realise it was yours; great writeup) I used a 256Kx8 RAM chip I had lying around and made two 32K pages switchable through unused TMS9901 I/O pins. Still haven't got a use for it though 🙂
  9. I have used several different solutions to add 32K to consoles and none of them had trouble fitting under the shielding. There is at least one IC height space between the shielding and the motherboard due to the TMS9919/29 heatsink. One thing to keep in mind is that, unless you have a specific reason, the speed gain is not spectacular by any means and there are some programs that are incompatible with the 16-bit mod. I have attached the 8-bit mod I have used in my current console. Jochen TI 32k Mod.pdf
  10. I have built one of the citrus3000psi boards (no idea if they are still available). My console now outputs RGB through the video connector. I use a cheap Scart RGB -> HDMI converter from Amazon to display on a computer monitor. Initial image was too red to my taste so I experimented with a resistor in the Red line inside the Scart connector and settled on 68R. Much, much better result that the composite -> HDMI converter I used before. )
  11. Really appreciate the Fortran education here Vorticon; great demos. It has been a very long time, to have it up and running on this restricted hardware is a treat. It would be quite useful if it had some string-handling capabilities added.
  12. Adding 32K would mean either a complete redesign or an additional shield; since there are a couple of (rather easy) ways of adding 32K to a vanilla console already it won't be on the shortlist I think. A hard drive image on SD is something I have been thinking about after chatting to others working on similar ideas. it's certainly doable by changing the DSR and sketches. I am working on remote (network) storage, HD image support could be part of that.
  13. Hmmm yes it would be handy to have listing files as a keyboard shortcut for instance. Probably need to go down the route of a user-defined interrupt (>83C4)? You could shorten the CALL names for starters 🙂
  14. Moving pictures say more than a 1000 pictures: https://youtu.be/MDsME0TLIYE
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