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Hans23

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About Hans23

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  1. I ordered a whole bunch of M25P16's from different sellers at AliExpress. They were very cheap and all worked fine. I remember that Matt Haggerty mentioned other types that could be used but I could not find the message last time I was stocking up and then ended up on the Aliexpress route. If you figure out other types that work, please share.
  2. There seem to be quite some people who still want F18A's - I will be going to build a few more, but it won't be before later this summer before I get to it. I'll reach out to everyone who is on my list once I'm finished with the builds. -Hans
  3. This does not match my experience. Most chips that I bought from various suppliers are genuine parts. When it comes to older types, they are usually salvaged from old equipment and I encountered batches in which one or two of chips of a lot did not work, most likely because they were damaged in the extraction process. I have also heard of mass remarkings, but it seems that this practice is only economical for higher-priced parts, for example to sell a slower CPU as being a faster one. The most important advice when buying vintage chips from chinese suppliers is to test them as soon as they arrive in order to get refunded for those that do not work.
  4. Hans23

    WTB F18A

    I don't currently have any F18A's available, but I'll probably build a few more in later this summer if there is enough interest. I have a waiting list that you can get yourself onto to express your need in a non-binding form. I'll reach out once I have boards built.
  5. Jim contacted me by email as this seems to be a board that I have built. I would ask anyone who has problems with F18As that I have built to get in touch with me for support instead of asking Matthew Haggerty. I don't have a diagnosis for this board yet, but I'll probably send out a replacement board and look at the faulty one once it is returned to me. -Hans
  6. I'm away from the workshop now, but I did some measurements on the TIM9904ANL - It generates the four clock phases with 3 Mhz each, so I guess that the crystal is OK (it looks stock, same type as the one that clocks the VDP). As I have the VDP RAM in sockets now, I'll try swapping it as soon as I have some replacement chips. When I fitted the sockets, however, I swapped the chips around and that did not change the error behavior all that much, so I'm not quite hopeful regarding that. Anyway, thank you for your help so far, I'll spend some time with the machine next weekend and may get back with further questions or diagnosis results.
  7. I'm a bit further in, but no wiser: The machine exposes a weird timing behavior when and if it goes to the start screen and to TI Basic. The initial beep is delayed by several seconds (i.e. the start screen shows, but the beep comes much later). Likewise with selecting TI Basic - It seems to take longer to start than usual until the beep, but I can't get to the Basic prompt anymore. I have swapped the GROMs, the CPU, the VDP, the 9901, the bus mux chips and the RAM. I have also tested all the caps and they are nominal. Voltages are OK (I tried different PSUs), and the clocks all seem to be good as well. I found that the TIM9904 is incorrectly labeled as being an LS362 in the schematics and the pins are not correctly labeled, which was a bit puzzling at first. I'm now wondering whether there might be a source of interrupts or wait cycles that is slowing down the start process, but I'm more in fantasy land here Any further clues would be appreciated (but it will be a few weeks before I can dig deeper).
  8. Hi, does anyone recognize this failure mode? The machine starts into TI Basic, but it seems to take a bit longer then usual. The cursor quickly flashes for a short period, then stops flashing. Finally, the machine crashes, displaying just the empty blue screen: Thanks, Hans
  9. I bought the TMS9900 from Shop5037076, the TMS9901 from InShop Chip.
  10. I have bought several TMS9900NL and TMS9901 on Aliexpress and they worked fine. Always test your chips as soon as you receive them so that you can get a refund if they don't work.
  11. What happens if you try to go into basic? Do new characters appear on the screen at all, or does it stay blank?
  12. My PEB has a similar problem - It seems to be caused by the case breakout being a tight fit and the switch being mounted so that it bends easily. Other than replacing the switch (which I'd find a bit ugly), has this problem be solved by others and how? Thanks, Hans
  13. Nice, thank you both! I'll give the OSSC at try, I have one here and never tried it with the TI.
  14. The tms-rgb that I mentioned converts the YPbPr signal to RGB. This might not be necessary as YPbPr is commonly referred to as component video and there should be TVs that can directly display it. I tried with my Samsung screen but finally gave up and went the RGB route. Do you know of any working solution that converts the YPbPr output produced by the TMS9929A to a standard component video signal?
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