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tep392

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tep392 last won the day on January 5 2018

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About tep392

  • Birthday 03/01/1967

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    Peoria, IL

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  1. Yes, that seems like an easy solution. Maybe the power usage was within the limits of the design requirement, so they felt no need to make it any more complex.
  2. You sir are correct. A NIB still in shrink wrap 1020 sold on Ebay for $100 two months ago.
  3. Great project! Coincidentally, I was doing something similar over the holiday's to reproduce a serial and cassette I/O board for the Altair 8800. I didn't have access to a bare board, but did have high quality photo's of the front and back to use. It presented a few challenges, but the board complexity is nothing like the 1450 you are working on. This was my first board design and I used ExpressPCB, which I will never do again. They will only give you gerbers with a board order, so when the inevitable corrections needed to be done, I had to modify the gerbers by hand. ExpressPCB is seriously over priced. I did learn a lot from the experience though.
  4. For those of you who are interested in the inner workings, here are some images from the adjustment of the PLL. This is a Kansas City standard test signal (1200/2400Hz) with the corresponding digital conversion. I adjusted for KC standard. After adjustment, switching to MITS standard test signal (1850/2400Hz), and checking digital signal is good. The adjustment of the PLL is not the same for both standards. There is a bodge added on backside of board to switch in a parallel resistor when using MITS standard so that the trim pot doesn't need to be readjusted between the two.
  5. Front side view. I used the board to read in the Altair 8k BASIC cassette bitstream and then write it back out to cassette using the KC standard. I had to write the copy program and key it in on the front panel. Some old school pirating there.
  6. The MITS 88-UIO board is done! I had a couple bugs to chase down, but it seems to be working perfectly now. Here's a pic of Altair BASIC 4.0 loaded from cassette.
  7. It is cool to see the 2600+ enabling some of those XM features. If the firmware gets to the point where it can support POKEY/YM sound, RAM and High Score Cart, then it will have the most useful features of the XM. I have four games, Beefdrop VE, Froggie, DK XM and PMC 40th that don't have sound chips in the cart and would benefit from those features. I wasn't planning to buy the 2600+, but seriously considering it now.
  8. That is great news! Is this with the Beta firmware? I thought I read that it didn't have sound with the original firmware. Or maybe that was the PK version that someone tested. It's been to long for me to remember, but my guess is that I would have disabled the external XM POKEY when the chip was added to the cart for the PK version.
  9. I'm making progress on this board. All components are confirmed and I have orders placed. The board design is coming along well. I've finished the bottom of the board, the easy part, and now need to work out all the top side traces that are hidden by components.
  10. As already stated, the two small boards are for the 810 drive. Both boards were part of two design improvements that Atari made to the 810 drive after it was initially released. I copied the notes below from the Best Electronics website which explains the issues. Best Atari 810 Tech Tip: Atari 810 problems fall into a few different basic reasons / problems. A dead (no LED or LED's works but no mechanical movement) 810 is usually a bad rear Atari 810 Power board. It could also be a combo of both a bad rear power board and sideboard problems. A mechanically working 810 disk drives that have Read (boot errors) or Write (can not format a SSSD 5 1/4 Floppy disk, which is one of the true tests of the health of any Atari 810 or Atari 1050 Disk drive) problems is usually a 810 5 1/4 Disk Drive mech. problem. But could also be a combination of both a bad 810 disk drive mech. and bad 810 sideboard problems. Early made Atari 810 Disk drives had two known major problems. On early production runs of the 810 sideboards, they did not have the 810 Data separator board plug in upgrade daughter board (the WD 1771 disk controller chip plugged directly into the side board). The second known problem was the single rear 810 power board. Both were known to cause all kinds of problems with early Atari 810 disk drives and the only way to fix them was to add the 810 Data separator board and install the 810 improved rear power board. The Atari 810 disk drives without the Data separator board had all kinds of Read and Write 810 Head problems. The single 810 rear power boards had all kinds of speed problems that seem to change all of the time without making any kind of speed adjustments on the single rear 810 power board. Both known 810 problems we latter fixed in the Atari 810 production run with a new plug in 810 Data Separator board (which cured most of the 810 Read and Write electronic data problems). The second Atari 810 Major problem was cured with what is known within Atari Engineering as the Atari 810 Grass Valley board set below (where in California it was designed). This Atari Engineering Grass Valley 810 new board set cured all of the Atari 810 speed problems. It consisted of a new redesigned / improved replacement 810 rear power board and a second daughter board (sat over the 810 Disk Drive mech. and was connected to the rear 810 board with a 10 pin wire harness and to the 810 Head wire harness). The second Grass Valley 810 daughter board helped to separate and boost the Atari 810 disk drive Head signals. Also the Atari 810 Disk Drives that used the Tandon 5 1/4 internal Disk Drive mechs, had a very high failure rate of the Tandon access front Lift door (like a garage door opening) white pivot pens breaking. The second Gen. improved Tandon 810 lift door assemblies in stock.
  11. Thanks for posting the article! My first experience with computers and BASIC was in my high school lab of TRS-80 Model 1's. I would stay after school to play Star Trek and mess around in BASIC. The next year they updated the lab with Apple IIe's. My electronics teacher had a system in his office that I think was S-100 based, but I can't remember which system he had.
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