Jump to content

AwkwardPotato

Members
  • Posts

    159
  • Joined

  • Last visited

Profile Information

  • Gender
    Male

Recent Profile Visitors

4,992 profile views

AwkwardPotato's Achievements

Chopper Commander

Chopper Commander (4/9)

134

Reputation

  1. Yes, the audio coming out of the tape recorder is fed into the audio input on the sound chip. If you can find the tape recorder cable for the 4A, you can mix the audio from practically any device with a 3.5mm jack into the output of the computer. The audio input line is also present on the side I/O port of the computer; that's where the Speech Synth accessory's audio gets mixed into the computer's output.
  2. To second what Stuart said, I think you may find salvaging 4116s to not be worthwhile when they can be found inexpensively online. Removing the DRAM on these boards with solder wick/a manual vacuum tool is a right pain in the neck; the less desoldering you have to do with these, the better. The joints for the power pins especially sink a lot of heat, and it's easy to accidentally destroy the through-hole plating. An oft-recommended approach for the DRAM is clipping each of the IC legs and pulling them out one-by-one with the soldering iron.
  3. Just for the record, those green parts are film capacitors, and it is *incredibly* uncommon for those to fail in these types of applications. If any of the capacitors are going to fail, it'll be the red/black aluminum-can electrolytics (and even those generally seem to be fine in the QI power supply). Also, if the replacement capacitors are ceramics, be aware that some types of ceramics' capacitance will change significantly depending on the DC voltage applied to them. This absolutely can influence circuit operations, the film caps on the other hand are immune to this effect.
  4. Verify that all the voltages coming off the power supply are still within spec. I mention this not because I think it's the root cause of your sound issue, but because RV1 may be an adjustment for one of the power supply outputs (I don't have one ATM to verify this). The sound IC is right next to the large hole in the motherboard that one of the case standoffs protrudes through. Chances are that it's the fault, rather than the power supply.
  5. AFAIK the datasheet for the TMC0430 GROMs has never been located. If you want to verify the pull-up/pull-down circuit, probe the collector of Q500. It should swing between 0-5V and follow the DBIN# signal. If the low level is greater than a couple hundred mV, the transistor is bad, or its base resistor is open. If the high level is significantly greater than 5V, one of the diodes/R520/R521 clamping the collector voltage is open.
  6. Meant to specify, "where the larger composite tips really shine." Fine tips, some improvement. Chisel/bevel/knife, great improvement.
  7. Having used the FX-888 in school and the FX-951 at home, both with fine tips, there's for sure an improvement when using the 951's composite tip. That said, it's not a night-and-day improvement. IMO where the composite tips really shine is e.g. soldering the tabs on beefy surface-mount power transistors to copper pours with arrays of thermal vias. Just for the record, not trying to imply that the FX-888 is a bad soldering iron. My only qualm with it is that it's remained at the same ~$110 price point for years and years now -- the competition has come a long way
  8. Two models of soldering iron you'll often hear recommended for hobby work are the "classic" Weller WLC100 and Hakko FX-888D. The Weller model is power-adjustable (not the same as temperature-adjustable) unlike the old Radio Shack irons, is more than adequate for working on boards like the SAMS, and is fairly inexpensive. I used that Weller for several years, can definitely recommend, although I've upgraded again recently. The Hakko model has a leg up over the Weller, as the FX-888D is temperature adjustable. This particular Hakko isn't a great deal in 2022, though, and is outperformed by a long shot by Chinese-manufacture soldering irons like the Miniware TS100/TS80P (which are less expensive, and still reasonably well made). Also note that the market is flooded with counterfeit FX-888Ds. If you think you might get into slightly more "involved" soldering projects later, the Hakko FX-951 is pretty nice (that's what I'm using now). Unlike the WLC100/FX-888D, the FX-951 and the aforementioned Miniware models have combined heater+tip setups, and that allows the soldering iron to heat up waaayyyy faster (especially helpful when soldering to large components).
  9. 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?
  10. Would it still be possible to purchase a bare 4000B board?
  11. 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.
  12. 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.
  13. 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?
  14. 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.
  15. 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!
×
×
  • Create New...