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shoestring

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About shoestring

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    Dragonstomper

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    Male
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    Sydney
  • Interests
    C64, Apple, A8 & Amiga junkie. Video game & electronic repairs, homebrew dev (arcade diagnostics software), guitar & music.

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  1. Don't you mean c50? Try a polymer solid electrolytic cap ( more reliable ) if you know c50 is bad. It's not rare for those to fail, just search the forum and you'll come up with some results. But I think you'll get better results if you try a proper 5v power supply.
  2. They can and they will, switch mode is inherently very noisy. They're not suitable for continuous use because they're not designed to filter switching noise sufficiently, all they need to do is charge. I'd say your filter needs a tweak. I used a DC-DC buck module in a power supply that I rebuilt which has some filtering but I could still see 150+mv of AC ripple on the 5v line under load, added an additional low ESR capacitor and a choke brought that noise down to around 30mv and cured the jailbar effect.
  3. Saw one for the first time in a shop window late in the evening on the main street in my city. It was an Amiga 1000 with the monitor facing the shop window and there was a fixed digitized image of a red Ferrari on the screen. I'll never forget it, I stared at that image for about 5 minutes in amazement before being pulled away by my parents. I couldn't believe what I was seeing because at the time, PCs were still using EGA graphics and my c64 had similar limitations. From that point on I had to have one but the A1000 was too expensive, we eventually got an A500 with 1.3 in 89 or 90 and the first game we bought was Shadow Of The Beast II, it was $79 which was really expensive in 1990. My brother loved playing Sensible Soccer and Kickoff where as I loved playing Hybris and Silkworm. I had a friend over all the time and we'd watch the latest demos and read all the scene disk mags, he loved downloading protracker mods and would have them playing in the background whilst looking at stuff on the internet. I don't have an Amiga anymore, they are just too expensive to maintain and keep up to date. But I'm still doing a lot of assembler programming in vasm and mess around in UAE. Currently playing around with gfx in mame, dumping them and implementing tilemaps via the copper/blitter. Amiga was a great system, unfortunately it wasn't very well balanced. AGA wasn't much of an enhancement in 92, it was fairly pointless without an upgrade of the blitter or at least a tilemode in hardware.
  4. Dave Haynie was designing the next system architecture in such a way that make would make the next system more modular. That is, separate the graphics from the audio and then I/O. He designed a custom bus that would solve those problems however, PCI came out which solved that problem and did it much better than he did. Commodore actually loved to use standards as long as they weren't rubbish. The next generation Amigas would have had a PCI bus, graphics would have lived on PCI and there would have also been a PCI to Zorro III bridge. Dave had already speced out PCI interface to AA and AAA so the gfx would have lived on a card eventually.
  5. I have one of those PAL International NTSC models. I recently converted it to NTSC to get colour by swapping the crystal and IOU. My write up is here for those interested https://www.jammarcade.net/apple-iie-enhanced-platinum-ntsc-50hz-to-60hz-conversion/
  6. Yes, bin it while you still have a working machine.
  7. Maybe you can use this type of SRAM on a daughterboard to replace the 4 bit rams in the 600xl and XE machines. It's for the c64 but I can't see how this wouldn't work in an Atari computer.
  8. So many possibilities ( mmu, cpu, osrom, ram, 74LS logic ). Maybe even a single bent pin hiding between the top of the socket and bottom of the chip. Do you have any carts to try in the machine ? ( star raiders ).
  9. You can build this overvoltage circuit below for relatively cheap. I modified my Atari and C64 power supplies using a variation of this circuit which introduces a voltage clamp and fuse on the 5v output. http://www.electronicecircuits.com/electronic-circuits/7805-5v-1a-regulated-power-supply-with-overvoltage-protection-circuit Instead of the 7805 I used a DC-DC module and adjusted its output to around 5v, then trimmed the board to fit inside the case. Most of the parts are hidden under the DC module but it's essentially the same circuit. The only changes I made were to the zener diode value from 6.2v to 5.6v and I also added a choke ( not pictured here ) to reduce the switching noise exposed on the 5v line. Winding the pot on the module past 5.7v blows the 2a fuse and protects my machines. Have been running this setup happily for about a year now with no problems. You could also use a TPSM84205EAB, which is a drop in replacement for the 7805.
  10. Only because I disagree with "Macintosh Color" more than Apple II.
  11. I remember Bil Herd saying that they had a warehouse full of those machines but it's unclear where their final destination was.
  12. Arguably it was 3 computers in one with a Z80A or B and could run CP/M, albeit rather slow compared to most other CP/M systems.
  13. The 555 timer is part of the reset circuit, so if it's broke the CPU will just sit there waiting for a RST pulse with its outputs stuck. But I don't think that's OP's problem.
  14. I had the opposite problem with the same result as expected. NTSC 800 and a Commodore 1084S-P1 ( PAL ). So a black and white picture is normal. To solve this I use a Sony PVM 9", which handles both NTSC and PAL.
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