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About shoestring

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

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  1. I haven't had much luck identifying bad DRAMs using the piggyback, I've had some success identifying bad SRAM ( 2114s, 2128/6116 ) with that method. The mT DRAMs I've dealt with have mostly shit themselves to the point where the chip is completely dead or the outputs are floating, I haven't really seen any other failure modes beyond that with these ones.
  2. Galaga, being a fast shooter really needs rot90 monitor orientation ( screen rotated vertically ) to make allowance for distance between player and enemies.
  3. Untitled.mpg Spent a couple of hours on it tonight and it's looking slightly better albeit many bugs. Rather than doing them by hand, the bit patterns in the tiles are now horizontally flipped during initialisation. Haven't implemented any DLIs yet, so excuse the jerkiness. Have some ideas to deal with the vertical stripes in all the graphics.
  4. Here's a very early Dino Eggs WIP I just started a couple of weeks ago. Disassembled original code and working with source derived from that. Yes it needs quite a lot of work! But essentially the Atari is running the Apple II code in an 130xe config. I'm using xbios to load all the original images from the Apple II straight into the available memory banks. At least the bottom row is showing up correctly, looks as though I'm on the right track in terms of using a lookup table to mimic the Apple IIs weird display layout. video.avi
  5. Well, I apologise if it looks as though I'm trying to derail a thread but I also felt the issues were somewhat related and could help someone else out. I've been literally pulling my hair out trying to find a cause. Just an important note before you read on, both ANTICs are C012296D-01 ( replacement and original ). Here is the original. With the replacement, the pmg issue was still present but only for a few seconds and completely disappears as the machine warms up ( maximum 10 seconds, average 5 seconds ). I can definitely live with that. I'm no expert but I don't believe my ANTICs are faulty, there are just some subtle variances where the issue may be exhibited. I had the machine running for hours on end with the old ANTIC and the problem was permanent. Unlike the replacement, the issue does not return as long as the machine isn't powered off for a significant amount of time then powered back on. vid.mp4 Edit: Also, I forgot to mention that there was some PMG glitching at the left and right hand side of display when the screen saver kicked in. It's completely gone now with the new ANTIC.
  6. Like this. It's not present in the loader screen though, at least not for me. So I temporarily replaced the GTIA with a PAL version and thought I'd found the culprit. The replacement GTIA came but didn't help. I do have a spare ANTIC to try sometime tomorrow. Thanks for the heads up.
  7. Could be the 4050 hex buffer. These are CMOS and easily damaged
  8. Never worked on late 80s c64 PCBs, have worked on several from 83 and they are built well. You would have to be fairly careless or inexperienced to lift a trace. The 130xe board that I have was probably one of the easiest I've ever worked on in terms of how quick it took to remove all the chips and socket them.
  9. I think the quality is quite good on all Atari 8 bit PCBs, even the XE. But then again, I'm comparing those against the quality found in arcade pcbs I've worked on from the same era which are horrendous.
  10. I've done the mod on a 600xl, yes the instructions are a bit confusing. It's an NPN transistor, so the emitter is pin 1 on the 2n2222 I can provide some gut shots of the machine as soon as I get home if that helps.
  11. The stock video output should be miles better than the one produced by a 130xe.
  12. It's not an early Apple II revision machine for hoarding purposes. And they produced a lot more of these, they are not going to a few hundred thousand dollars anytime soon.
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