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About ClausB

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    River Patroller

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    space and rocket history, astronomy, photography, math, computer programming, physics, digital electronics, Atari, aviation, sports cars, Star Trek, Star Wars, Doctor Who, my family, to name a few

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  1. I'm betting the bad chip is the one with the big, red X on it!
  2. My little retro cubby. Clockwise from upper left: Exidy Sorcerer, Apple IIc, Sinclair ZX80, TI SR-56, Atari 400, Atari 800XL, Atari 800, LCD with S-video and 4:3 mode.
  3. There's one for Apollo, so we need to wait another 8 years or so. https://haynes.com/en-gb/apollo-11-50th-anniversary-edition
  4. About ten years ago I decided to resurrect Old #26, my rare pre-production 800. When it didn't boot up I tried the usual chip reseating bit. Those lovely, precious, white chips would not budge from their sockets. I pried harder, even though I feared I might snap one in half. I got lucky and it finally came loose, though it left half of one gold pin in the socket. Idiot! I left the other one alone and fashioned a way to make contact between the socket and the remaining stub. This happened after I took the photo below. After much troubleshooting I found the CPU was bad (the big black chip below) and the rest of the old girl worked fine. Hmm, it's about time to fire her up again. I hope I'll be a better curator this time.
  5. Strange, I have not heard from the publisher since July! Yes, the mod is similar to my old 1982 article.
  6. Was that for the 6800 family? Can't do that in 6502 nor Z80.
  7. Yes, in the color adjust circuit, as BillC mentioned. You should still fix it.
  8. Ouch! Here's a mod which eliminates 12V and -5V from the RAM board and uses 4164s for 48K on one board:
  9. If you look at the circuit before the 2 "jumper" cuts were made and the 2 "bodge" wires 26 & 27 were added, it appears that the configuration register was used instead of PB5 and PB6 for bank selection. So maybe the original boffin designed it for pure 130XE compatibilty with an optional extension to 256K.
  10. Correction to the label for wire 2: /A14 A15 goes through the switch. Possible mistake: U6 pin 5 should go to ground. With those, the banking circuit is equivalent to what I drew above except that it includes HALT, so it won't bank for ANTIC (not at all, unlike the 130XE). Otherwise it should behave as a RAMbo, as we saw in the test screen.
  11. It appears the register outputs go to two gates and the "jumper" cuts, so they no longer have any effect on the circuit. The rest of it seems to be equivalent to the circuit I posted, but I'll double check.
  12. While Chesh is getting cross-eyed starting at wires and chips, I've teased out another detail from his schematic. There is only a single 2-bit configuration register at address $D6xx. Purpose still unknown.
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