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Tandy 1000 RLX General Maintenance

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Tandy 1000 RLX hard drive model, front (Jim Leonard)
Front of a Tandy 1000 RLX hard drive model (photo: Jim Leonard, CC BY 3.0).

Routine care of the Tandy 1000 RLX and RLX/HD covers the fanless power supply, ZIP memory, the 1.44 MB floppy drives, the XT IDE hard disk, the clock battery and the EEPROM settings. The RLX shares its case and supply design with the Tandy 1000 RL, so Tandy 1000 RL General Maintenance also applies. The notes below cover what is different. Tandy's service manual for the RLX (25-1452) could not be obtained.[1]

Power supply

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The supply is rated at 25 W and the RLX has no fan.[2] Its connector pins and parts are on Tandy 1000 RL Capacitor Replacement Guide. An RLX/HD owner planning a modern replacement was advised that a 50 mA -12 V rail should be enough, as -12 V is probably used only by the serial port, and that 18 AWG wire is adequate for a short harness.[3] Measure the machine's actual draw with the original supply before choosing a replacement.

Memory

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Model Standard Upgrade
RLX 512 KB Four 256K x 4 ZIP DRAMs, 100 ns, in U23-U26
RLX-B 512 KB Four 256K x 4 ZIP DRAMs, 100 ns, in U2, U4, U5 and U9
RLX-HD, RLX-HD-B 1 MB Fitted at the factory

Source: Tandy 1000 FAQ.[4] The FAQ names the Samsung KM44C256AZ-8 as a suitable ZIP chip; Radio Shack sold the upgrade as kit 25-1083.[4][5] With 1 MB fitted, 384 KB is available as extended memory; if HIMEM.SYS does not find it, use the /M:2 option.[4]

Floppy drives

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  • The RLX's controller takes only high-density drives, and its 1.44 MB drives take their power through the data cable. Replacements must be Tandy-style drives, or the cable must be modified.[6]
  • An owner who fitted a Gotek floppy emulator needed a Tandy adapter board because of the way the cable carries power.[3]

General drive cleaning is covered on Floppy Drive Repair.

Hard disk

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  • The SmartDrive interface is XT IDE; Tandy's 20 MB (25-1047) and 40 MB (25-1048) SmartDrives were installed with HINSTALL from DeskMate.[7]
  • Only Western Digital MFM or RLL controllers work in the RLX; the Silicon Valley ADP50T AT IDE card also works.[7]
  • To boot from the hard disk, set the boot device to DISK in SETUPRLX.[7]

Clock battery

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The RLX has a DS1215 clock chip and a CR2032 cell in a holder.[1] Replace a flat cell with another CR2032. The setup settings are in the EEPROM, not backed by this cell.[8]

EEPROM and setup

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  • Settings are changed with SETUPRLX. The serial EEPROM is at U3, in an 8-pin socket.[8][1]
  • If the BIOS reports an invalid configuration, run SETUPRLX and save the changes so that the EEPROM matches the hardware.[9]
  • The PS/2 mouse port must be enabled in SETUPRLX.[10]
  • The parallel port's bidirectional mode is set in the setup program.[11]

Expansion

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  • The single slot is 8-bit; cards must be 10 inches or shorter, and space inside is tight.[12]
  • There is no coprocessor socket, and the 386 and 486 daughterboards made for the TL do not fit.[13]
  • The RLX-B and RLX-HD-B have 8-pin mini-DIN joystick ports; Tandy sold adapter 26-0284 for 6-pin joysticks.[14]

Maintenance checklist

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  1. Check the rating label before connecting the mains.
  2. Inspect the main board for burnt tantalums and the supply for leaking capacitors.
  3. Replace a flat CR2032 clock cell.
  4. Use only Tandy-style 1.44 MB drives on the floppy cable.
  5. Note the SETUPRLX settings before changing anything.
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References

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  1. ↑ 1.0 1.1 1.2 Tandy National Parts, bill of materials 250-1452 "Tandy 1000 RL-286", January 1995, 25-1452.txt, TVDog's Tandy 1000 archive (retrieved 2026-10-21). Lists service manual 25-1452.
  2. ↑ Radio Shack, computer catalogue RSC-23 (1992), p. 8, "Home office and family PCs", page scan at RadioShackCatalogs.com (retrieved 2026-10-22).
  3. ↑ 3.0 3.1 "Tandy 1000 RLX/HD power supply replacement (6-pin connector type, wiring gauge, etc)", Vintage Computer Federation forum, July 2026, thread. Posts by TandyDean and Plasma, 18 July 2026.
  4. ↑ 4.0 4.1 4.2 Jeff Hayes, "Tandy 1000-series FAQ", version 2.52, 25 October 2005, TVDog's Tandy 1000 archive (retrieved 2026-10-21). Sections II.A.1 and II.A.5.
  5. ↑ Radio Shack, 1993 catalogue, p. 164, "512K Zip Memory Kit", page scan at RadioShackCatalogs.com (retrieved 2026-10-22).
  6. ↑ Hayes, "Tandy 1000-series FAQ" (2005), sections II.C.1, II.C.2 and II.C.5.
  7. ↑ 7.0 7.1 7.2 Hayes, "Tandy 1000-series FAQ" (2005), section II.D.1.
  8. ↑ 8.0 8.1 Hayes, "Tandy 1000-series FAQ" (2005), section II.K.8.
  9. ↑ Hayes, "Tandy 1000-series FAQ" (2005), section III.F.3.
  10. ↑ Hayes, "Tandy 1000-series FAQ" (2005), section II.G.2.
  11. ↑ Hayes, "Tandy 1000-series FAQ" (2005), section II.H.2.
  12. ↑ Hayes, "Tandy 1000-series FAQ" (2005), sections II.A.4 and II.I.3.
  13. ↑ Hayes, "Tandy 1000-series FAQ" (2005), sections II.F.1 and II.F.2.
  14. ↑ Hayes, "Tandy 1000-series FAQ" (2005), section II.J.1.


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