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Tandy 1000 HX

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Tandy 1000 HX
Tandy 1000 HX with monitor and printer (Jesster79)
A Tandy 1000 HX with monitor, joystick and printer, photographed in 1991 (photo: Jesster79, CC BY-SA 3.0)
Specifications
ManufacturerTandy Corporation, sold by Radio Shack
TypeCompact desktop personal computer (IBM PC compatible)
CPUIntel 8088, 7.16 MHz, can run at 4.77 MHz
Memory256 KB, expandable to 640 KB with a PLUS memory card
StorageOne or two 3.5-inch 720 KB floppy drives; port for an external drive
DisplayBuilt-in Tandy video, PCjr and CGA compatible
SoundThree-voice sound chip at U19 (SN76496 or NEC 8496)
PowerInternal switching supply
OS / FirmwareTandy MS-DOS 2.11R in ROM and Personal DeskMate 2
Model no.25-1053

The Tandy 1000 HX is a compact IBM PC compatible computer in the Tandy 1000 family, released in 1987 as an updated Tandy 1000 EX. It keeps the EX's architecture and PLUS expansion connectors, but has two 3.5-inch drive bays in the front panel, MS-DOS 2.11R in ROM, and a serial EEPROM that holds its configuration.[1]

History

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According to Wikipedia, the HX boots quickly because DOS is in ROM and the start-up memory test was removed, and it shipped with Personal DeskMate 2. Most later versions of MS-DOS run on it, but DOS 4.0 does not, and the installer for MS-DOS 6 can corrupt the EEPROM.[1] The TVDog model list gives catalogue number 25-1053.[2]

Hardware

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No technical reference manual for the HX has been found. The Tandy 1000 EX manual covers the shared architecture, and the details below come from it where owners' reports show that the HX uses the same part.[3]

Power supply

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The HX's supply appears to be the EX's 28 W design. A photograph of an HX supply board shows transformer T1 marked TO-4349, the transformer in the EX manual's parts list for supply 8790083, and the references printed on the board, among them D9, D11, IC1, C14 and SK2, match that supply's parts list.[4][5] One owner swapped the supplies of his EX and HX while fault finding, and an open hardware replacement board is designed for both machines.[6][7] Radio Shack's 1988 and 1989 catalogues give the HX supply's output as 25 W, against 28 W for the EX, so check the rating label on the supply in hand.[8][9] The EX supply's service data is on Tandy 1000 EX Troubleshooting Guide and Tandy 1000 EX Capacitor Replacement Guide.

Drives and storage

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The HX's 3.5-inch drives take their power through the data cable, so a standard drive must not be connected to that cable unchanged. The HX has a free bay that can hold a 3.5-inch hard disk, but no power cable for it, and a hard disk controller needs the DMA on the PLUS memory card.[10] Like the EX, the HX has a port for Tandy's external 360 KB and 720 KB drives.[10]

Configuration

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Settings live in a serial EEPROM and are changed with Tandy's setup program.[1][11] To boot a newer DOS from disk, the FAQ says to set the primary start-up device to DISK in the setup program; with the HX set to boot from ROM, CONFIG.SYS and AUTOEXEC.BAT on drive A: are ignored.[12]

Known faults

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  • A buzzing or hissing speaker whenever the screen is idle. One owner traced it to the NEC 8496 sound chip at U19; replacing it with an SN76496 removed the noise.[6] See Tandy 1000 HX Troubleshooting Guide.
  • Failed supplies. The same owner's HX arrived dead with a supply that needed repair.[6] See Tandy 1000 HX Capacitor Replacement Guide.
  • A corrupted EEPROM can stop the machine at the memory count; the FAQ gives recovery steps.[11]
  • Worn cooling fans. Owners have replaced the HX fan; one reports that it is a 60 mm part.[13][14]

Documentation

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References

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  1. ↑ 1.0 1.1 1.2 "Tandy 1000", Wikipedia (retrieved 2026-10-21). Sections "Tandy 1000 EX and HX" and "1000 HX".
  2. ↑ Jeff Hayes, "models.txt", TVDog's Tandy 1000 archive, 2005 (retrieved 2026-10-21).
  3. ↑ Tandy Corporation, Tandy 1000 EX Technical Reference Manual, catalogue no. 25-1510, 1986, hosted as File:Tandy 1000 EX Technical Reference Manual (25-1510, 1986).pdf.
  4. ↑ Blake Patterson, photograph of a Tandy 1000 HX power supply board, 2019, CC BY 2.0.
  5. ↑ Tandy 1000 EX Technical Reference Manual (25-1510), parts list for switching power supply unit 8790083 (T1: TO-4349), PDF pp. 102-104; schematic 3P-M1-0163, PDF p. 107.
  6. ↑ 6.0 6.1 6.2 "Tandy 1000 HX noisy speaker with idle screen", Vintage Computer Federation forum, February 2025, thread. Posts by Hamsterbasher (1, 2, 4 and 22 February 2025) and daver2.
  7. ↑ tgotright, "Tandy1000EX-HX-ATX", GitHub repository, 2021: "Drop in replacement Power Supply board for Tandy 1000 EX and HX computers" (retrieved 2026-10-22).
  8. ↑ Radio Shack, computer catalogue RSC-19 (1988), pp. 9-10, Tandy 1000 HX and Tandy 1000 EX specifications, page 9 and page 10 scans at RadioShackCatalogs.com (retrieved 2026-10-22).
  9. ↑ Radio Shack, computer catalogue RSC-20 (1989), p. 21, "The fast-loading Tandy 1000 HX", page scan at RadioShackCatalogs.com (retrieved 2026-10-22).
  10. ↑ 10.0 10.1 Jeff Hayes, "Tandy 1000-series FAQ", version 2.52, 25 October 2005, TVDog's Tandy 1000 archive (retrieved 2026-10-21). Sections II.C.2, II.C.4, II.C.5 and II.D.1.
  11. ↑ 11.0 11.1 Hayes, "Tandy 1000-series FAQ" (2005), sections II.K.8, III.A.1 and III.F.1.
  12. ↑ Hayes, "Tandy 1000-series FAQ" (2005), sections III.A.1 and III.A.3.
  13. ↑ "Is the power supply fan in the 1000SX really needed?", Vintage Computer Federation forum, March 2019, thread. Post by blackepyon, 8 March 2019.
  14. ↑ Blake Patterson, photograph of a Tandy 1000 HX with a replacement fan, 2019, CC BY 2.0.


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