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Derek Andrews

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About Derek Andrews

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    Space Invader

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  • Location
    Nova Scotia
  • Interests
    Voltmace Database and other 2650/2636 systems
  1. How important is a two-player option for a homebrew game for a retro console?
  2. Thanks, that is interesting but I honestly don't know if they ever actually sold any of those. But yes, I did all the design work for DAZRAM. Given that it was nearly forty years ago, I don't think I can add much beyond what is in the advert. One end plugged into the ZX81, presumably an expansion port, and it had a ROM with Z80 code that I wrote to allow the user to input 2650 machine code. The code was stored in a RAM and connected to the Database cartridge. Given that the user was going to have to write their program in assembler and convert it to machine code themselves, and the complexity of programming the console to do very much at all, it would have taken someone with a lot of perseverance to get very far. This was probably one of the crazier things I have ever been involved in, but I was getting paid to do it.
  3. The joystick circuitry is odd indeed, and I can't say that I fully understand it. The 2637 pins 8 to 11 that read the joystick switches are analog inputs that are measured by an analog to digital converter on the chip. The asymmetric values of the resistors and capacitors in the circuit (10k/470k ohm and 0.1/0.047 (uF?) ) must be significant, perhaps forming some sort of timing circuit, but that is just a guess. I have no idea what the jack plugs J1 and J2 are connected to or what role they play.
  4. Yes. The 74LS145 is used to output a logic 0 to one of the six sets of four keys each. The 74LS258 is used to decide which of the two handsets to read, and outputs the state of the four keys selected by the '145 to the low bits of the databus. http://www.ti.com/lit/ds/symlink/sn74ls145.pdf http://www.ti.com/lit/ds/symlink/sn74ls258b.pdf https://console5.com/techwiki/images/f/f0/Emerson-Arcadia-Schematic.png
  5. There are large solid areas for the joystick switches.
  6. I wonder why they leave the gaps in the contacts Why not solid round pads?
  7. A bit late replying on this, but yes, and for the record: The 'speed' of these memory chips is usually quoted as an access time. A -150 signifies a memory device whose contents can be accessed in 150ns. A -200 takes 200ns for the data output to be valid. Conversely, microprocessors are specified to work at a particular clock rate, for example the Z80 ran with a clock rate of 2.5 MHz, the Z80A runs at 4MHz, the Z80B at 6MHz.
  8. I finally broke down and bought myself not one, but two Voltmace Databases. It will be a while before I have the time to get them powered up on 110v and displaying their video, but in the meantime I plan to open them up and document their construction. I have a list of things I want to record (below), but wonder what others might like to see recorded for posterity. Photos of the original box artwork. Photos of the polystyrene packaging. Photos of the mouldings with dimensions. Photos of the circuit board, top, bottom and one superimposed on the other, from which a circuit diagram could be constructed. Parts list. Manufacturer and date code of all the IC's which may give a clue as to the approximate vintage of these two consoles. Ditto the cartridge wiring and construction. (My regional library has a 3D scanner and printers, so I will see if it is possible to scan the two parts of the cartridge mouldings and print new ones).
  9. Sorry, I guess I missed your post when you made it Carlsson. A bit of both really. I am working on a game, as time and enthusiasm permits, and have some other ideas too. I don't mind investing my time in the project as a hobby, but money is tight for me these days, and so far everything I have done has been with the WinArcadia emulator. I have no dreams of making money from the effort, but would like to cover some of the costs of buying a console and other hardware for test purposes, so wonder what sort of interest there would be in a new game, whether I could justify making cartridges, or just making binaries available for download and seeking support via Patreon. I might also make the source code and documentation available, either as a download or print on demand book. I am also interested in exploring just what the console could have done if the the cost of rom and ram were less prohibitive back in the early 80's.
  10. What I am looking for is something to plug into an Interton VC4000 type console that will emulate the ROM and RAM in a game cartridge. It would need to connect to a PC via cable, Bluetooth or Wi-Fi and would be used for the purpose of game development. Does such a thing already exist? It seems to me that something like this would be quite possible using something like an Arduino or Raspberry Pi, but don't want to re-invent the wheel if there is already something out there that will do the job.
  11. Yes, its a rca/phono type socket on the console, and yes it is analog rf. RCA-Ftype adapter, then coax cable to tv. Yes, I have a picture, just not very good and some games the colour contrast is minimal.
  12. I'm using a RCA to F type adapter at the console connected via coax cable to the tv. I will try going through the VCR, but need to get another coax cable first.
  13. Found it, but doesn't really help any.
  14. Not that I can see. I'll go through the menus again just in case I missed something, but there are no physical controls. Picture quality on VCR is fine though, so I don't think this is the problem.
  15. I recently broke down and bought my first ever console, an Atari Junior, along with a variety of cartridges, and have just got it hooked up to an NTSC crt tv. I'm none too happy with the picture quality in terms of colour contrast. Some games are playable, but Frogger has some things that are difficult to see, and Popeye is next to impossible to play as the platforms and ladders are only barely visible. I'm just wondering if this is normal for NTSC? I recall the tv engineer at Voltmace telling me that NTSC stood for Never Twice Same Color Or is there a problem: 1. Faulty console 2. Connection problem (impedance mismatch, connecting the RCA on the console to the BNC on the tv) The tv works fine with VCR. There doesn't appear to be anyway to adjust colour on it.
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