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About plazma

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    Space Invader
  • Birthday 03/02/1978

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    Oulu, Finland

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  1. Received the correct SRAM chips. Looks little better.
  2. You can use the VSP Lab program to check if your machine got the VSP bug. Let it run for few hours. The bug may appear after the chips warm up. https://csdb.dk/release/?id=120810
  3. VSP trick is used for horizontal scrolling. The VSP bug crashes machines when using sw with the VSP trick. One of the games using the VSP trick is Mayhem in Monsterland. Machines with the VSP bug may hang or have glitches when using SW with the VSP trick. With this SRAM board that bug is gone and VSP trick SW works. http://www.linusakesson.net/scene/safevsp/
  4. I made a compact PCB which replaces DRAM with SRAM and fixes the VSP bug. It fits 466 & 469 motherboards. I'll place some for sale after I receive the correct SRAM chips. I ordered wide SOIJ case by accident. It did fit the PCB anyway and I could test the protype. This should also work with 600XL. My 600XL is dead at the moment so can't test.
  5. Can the CPU be replaced with any 6502? R/W is on different pin but that would be an easy fix.
  6. I replaced the DRAM with 4464 chips which have been tested on a C64. PIA was soldered to the MB on the 800XL so I did not swap it.
  7. That memory test difference seem to be related how the self test program was started. With the command BYE you get two and half rows. Power up with OPTION-key down gives three rows in the test.
  8. Did some IC swaps between the 800XL and 600XL. The CPU seem to be dead. In the 800XL it gives mixed yellow/brown screen. Working CPU in the 600XL still gives red screen. All chips have been removed and reseated. DRAM was replaced with tested chips. BTW I ran the memory self test again a few times on the 800XL. Why does it sometimes test three complete rows of RAM and sometimes only two and half rows?
  9. I found an ATF16V8B chip from my C64 VSP bug fix circuit. I flashed it with my TL866II+ programmer with the jed file from "comment-1911484". It worked! Also tested with the chip from the 600XL and it also worked. Hint for others: the ATF16V8B chip is cheap and readily available. It is compatible with the GAL16V8 jed file!!! Make your own MMU chips OK. So this 800XL unit was easy since all hot ICs were faulty. Next I'll try to fix the 600XL. All ICs are rather cool. But now I can swap ICs from the working 800XL.
  10. I'll get that document and check it for diagnostics hints. I used a 5V 4.5A PSU I found in my garage. I measures it to give 5.15V and negligible ripple. I soldered a DIN connector to the cable.
  11. I've had 600XL and 800XL units laying in my garage for years. Today I soldered a video and PSU cable for them. Both give a red screen only. The 800XL now gives a grey screen. First I started to debug the 800XL. A simple touch test followed by measuring with an IR thermometer revealed two hot DRAM chips (9C above other chips) and a hot OS rom chip (13C above the other ROM). I replaced the three chips. I only had 27C512 EEPROMs so I made an 64kB image by copying the original image four times. The address pins 14 & 15 are high on the MB. There was a change. Now the screen is grey. A second round with the IR thermometer also found the U3 MMU to be hot. I found PAL & GAL chip sources from here: https://www.atarimax.com/jindroush.atari.org/achmmu.html Have anyone tried these? Do anyone have compiled files? I could buy a GAL16V8 from a local store and flash it. I measured the ICs on the 600XL and they were all cool. Some were only 5C warmer but I consider it to be normal. The ICs are socketed so I will try the MMU from the 600XL on the 800XL. If I get one of the machines running it would help with the second one with IC swaps. Any hints or tricks? I also have an oscilloscope and a logic analyzer. I have fixed multiple Commodore 64s but Atari machines are new to me.
  12. Buy a cheap keycap puller from eBay. The long wire model works great. It pulls up do there is minimal stress to the plungers.
  13. I'm interested but live in Finland. I can pay shipping.
  14. I bought two for 11$ including shipping. Will install and test.
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