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About AwkwardPotato

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  1. The disk controller responding only to even-numbered CRU writes is normal behavior. As for why DSR access breaks with the FinalGROM, I'm not sure. While it's possible that the electrolytic caps in the video amp went bad, chances are they're not the issue at play here. Couldn't hurt to change them, but the caps on the motherboard have proven to be rock-solid compared to many other devices of the time, and you'd be hard-pressed to find reports of them failing. The audio coupling into the video signal almost sounds like a grounding issue. Happen to be able to take a photo of the inside of the DIN plug on the video cable?
  2. Would it still be possible to purchase a bare 4000B board?
  3. Oh, yeah, and on writing TI disks using a PC with a 5.25/3.5" floppy drive: I've tried three different PCs manufactured between 1991-1999, and not one of them had a floppy controller capable of writing the SD disks required by the stock TI disk controller. AFAIK standard density/FM encoding was never really a thing on the PC, as such YMMV.
  4. Rube Goldberg Approach for TI File Transfer in a Pinch (STEPS 1-5 ONLY NECESSARY THE FIRST TIME): (requires XB, RS-232 card, a "straight-through" serial cable, cassette cable, and possibly a USB-to-RS232 adapter) Download MagicFM, a file transfer program written in XB, available on WHTech and elsewhere (Note 1, see below) Use Fred Kaal's Ti99Dir to extract the LOAD and MAGICFM files from the above disk image to a directory on your PC (Note 2) Use CS1er to convert the extracted LOAD and MAGICFM files (they're in FIAD format by default) to .WAV format Connect the TI to a PC/smartphone with the cassette cable. Start the TI in XB Play back both of your converted .WAV files, one at a time, load them on the TI, then save them to a blank disk, once again as LOAD and MAGICFM. You now have an auto-booting MagicFM disk. Connect the TI to your PC via a straight-through serial cable (a null modem cable will NOT work), using the USB-to-RS232 adapter if necessary Reset the TI with the XB cartridge & MagicFM disk still in Transfer files (in TIFILES format) as needed with XMODEM mode in your PC terminal emulator of choice NOTE 1: Arcadeshopper already has a MagicFM disk in stock, which saves an incredible amount of hassle NOTE 2: Several members have reported success transferring MagicFM from an emulated TI (MAME) to a real TI over RS232, rather than using a cassette cable. I was never able to get this to work, however. NOTE 3: Getting an HDX or TIPI will save you an even greater amount of hair-pulling. The most difficult part of the above method is finding the right terminal settings to use on the PC side by trial-and-error. If you're doing this on a semi-modern Mac, be prepared for a USB-to-RS232 driver nightmare. The above mess is how I prepped my TI for file transfer when I first got my PEB. I'm drawing this from several-year-old notes, and posting it here mainly in case future passerby already have most of the above hardware and want to transfer files with the least additional expense possible.
  5. Doubt this is directly relevant to @videofx's problem, but the E/A manual does state that different 4As handle XOP 1 differently (granted I'm not familiar enough with assembly yet to know how this is significant). In other words, perhaps not all 4As with the 1981 GROMs are created equal?
  6. AFAIK bad DRAM can't cause this issue -- if it was the only fault, there wouldn't be a steady beep, and you'd likely get a corrupt title screen. I'd first suspect the 16-to-8-bit multiplexer, it's made up of the three LSTTL parts above the CPU and next to the GROMs (74LS244, '245, '373). If any of those fails (mainly thinking of the '245 here), the CPU will be unable to read from the GROMs and the system will lock up before it ever touches the VDP RAM.
  7. From what I've gathered reading around here, four of the most popular v9938/v9958-based VDP upgrades for the 99/4A are the AVPC, EVPC(2), TIM, and the Mechatronic 80-column card. Are there any differences in function/implementation among these upgrades (besides mouse support being limited to the 9938), or are they all largely software compatible with one another? Thanks!
  8. Double-checked my TI's board and yes, the damaged part on yours is a 1uF 25V tantalum capacitor. A suitable replacement can be found here on Mouser, and it appears that the same part can be found here on eBay too (not affiliated with seller). Note that this capacitor is polarized, so the rounded-off/tapered side needs to face the TIM9904 chip.
  9. Hard to say whether that VDP will work or not. While the listing photo looks like it could be a genuine part, finding working VDPs on eBay seems to be extremely hit-or-miss nowadays. May be worth a shot, and perhaps other members here will be able to share seller recommendations.
  10. If the damaged component is the black one, right of center, in between the two blue wires, I *believe* it's a 1uF tantalum capacitor. Just to double-check: is the beep on your system a short tone, or one that continues as long as the system is turned on? If it's a short tone, check that your video cable is good, then try resoldering all the pins of the video connector on the motherboard. If you still don't have any video afterwards, it's likely that the VDP has failed.
  11. I missed the heyday of the TI and its contemporaries by a couple of decades so my main PEB (older push-button style) is permanently set up, noisy fan and all. No modern amenities here! It's a basic 32K, RS-232, two disk drives setup, although it may get an HRD in the future to make E/A use a little more comfortable. Also have a spare push-button PEB: cheap local pickup with 32K and disk controller, but missing the RS-232, flex, and drives. Sitting around in case I happen across a Geneve or an entire set of SNUG cards. I can dream
  12. It's a symbol found on many bottom-of-the-barrel phony TI parts. Seems that they only bother engraving one half of the TX...
  13. Do other programs accessing the 32K cause the system to lock up too? If not, it might be worthwhile to try one of the memory test programs out there.
  14. The LS257s on the 32K card are used to multiplex the row and column addresses onto the 4116 DRAMs. If any of the LS257s' outputs fails (hi-Z/floating in my case), reads and writes to certain parts of the 32K expansion will also fail. For a card like yours that locks up the TI at startup, I'd suspect one of the parts closer to the edge connector. The 74LS245 buffer comes to mind, and the voltage regulators are also worth checking just to rule out the obvious. The schematics for the 32K card can be found on Mainbyte.
  15. For sure! This PEB's disk controller was afflicted with a bad LS245 buffer several years ago.
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