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Tandy 1000 SL General Maintenance

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Tandy 1000 SL2 main logic board layout (Installation and Operation Manual p. 24)
The SL/2 main logic board from the owner's manual, with the jumpers and sockets labelled.

Routine care of the Tandy 1000 SL and Tandy 1000 SL/2 covers opening the case, the power supply, the drives, memory and other main board options, the jumpers and the EEPROM settings. The procedures come from the SL/2 owner's manual, the only Tandy document for the pair that could be obtained; the SL's technical reference manual (25-1516) could not.[1] Check each step against the machine, because the SL has a 5.25-inch drive in the upper bay where the SL/2 has a 3.5-inch drive.[2]

[3][4]

Opening the case

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  1. Turn off the computer and everything connected to it, and unplug the computer from the mains.
  2. Remove the two cover mounting screws at the back.
  3. Pull the cover outward to release it, as the manual's drawing shows.
  4. When refitting, replace and tighten the two screws before switching on.

Source: SL/2 owner's manual.[1] Photograph the cables before unplugging anything inside.

Power supply and cooling

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The SL's supply is rated at 67 W output.[3] Tandy's voltage limits and component data for the SL supply are in the technical reference manual, which could not be obtained. With the machine running, check for +5 V on the red wire and +12 V on the yellow wire of a drive power connector, and inspect the supply and main board for leaking or bulging electrolytic capacitors.[5] One owner has a dead SL main board with corrosion from leaking capacitors.[6] The serial EEPROM sits at U17 beneath the supply, so it is easy to disturb when the supply is removed.[6]

Another owner reports that his SL's chassis is affected by zinc whiskers and needs clearing from time to time.[6]

Floppy drives

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  • The SL uses standard 360 KB 5.25-inch drives.[7]
  • On the SL/2, drive A: is a Tandy-style 3.5-inch drive that takes power through the data cable, on pins 3, 5, 7, 9 and 11 (+5 V) and 29, 31 and 33 (+12 V). A standard drive on the unmodified cable can damage the drive and the computer.[7]
  • The floppy cable is straight, not twisted, so each drive's select jumper sets A: or B:.[7]
  • A second drive goes in the 5.25-inch slot. Break out the plastic panel by pushing it down, fit the mounting rails using the lower left hole marked A-B, and secure the drive and its two grounding clips. A second 3.5-inch drive needs adapter bracket 25-1076. Run SETUPSL2 afterwards.[1]

General drive cleaning is covered on Floppy Drive Repair.

Memory and main board options

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Memory expansion
Model Standard Maximum Chips to add
SL 384 KB 640 KB Eight 64K x 4 DRAMs, 120 ns
SL/2 512 KB 640 KB Four 64K x 4 DRAMs, 120 ns

Neither model has a jumper to change after adding memory.[8][3]

  • The maths coprocessor socket takes an 8087; Radio Shack sold the 8087-8 for the SL.[9]
  • The 8086 can be replaced with a NEC V30.[10]
  • The optional SmartWatch clock (Dallas DS1216E) has its own socket on the SL boards, not under a ROM.[11][1] Its battery is built into the chip, so a SmartWatch that has stopped keeping time is replaced as a unit.[12]
  • Expansion cards must be no longer than 10.5 inches.[2]

Jumpers

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SL/2 jumpers
Jumper Default Change to
Microphone/line audio, on the audio control satellite board E2-E3 (microphone) E1-E2 for a line-level source
Video interrupt, on the main board E2-E3 E3-E4 if a PCjr or Tandy 1000 game stalls

Source: SL/2 owner's manual.[1][13] Wikipedia confirms the microphone/line jumper on the SL's satellite board.[2]

EEPROM, setup and DOS

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The SL family keeps its settings in a serial EEPROM, not CMOS, and removing a battery does not clear them. Settings are changed with the model's setup program (SETUPSL or SETUPSL2).[14][1]

  • SETUPSL /F writes the factory defaults to the EEPROM. The /A and /B options reach settings that can leave the machine unbootable.[14][6]
  • To boot from a hard disk, set the boot device to DISK with MS-DOS as the start-up program.[15]
  • The FAQ warns that DOS 5 or 6 can scramble the EEPROM on Tandy 1000s with DOS in ROM, and that running a DeskMate program outside DeskMate can also corrupt it.[16]
  • Note the settings before changing DOS versions.

Keyboard, monitor and printer

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  • Use an XT keyboard, or an XT/AT switchable one set to XT. AT and PS/2 keyboards need a converter.[17][18]
  • Ctrl-Alt-Shift-V switches between colour and monochrome monitors and stores the choice in the EEPROM.[19]
  • The printer port is a card edge, so use a Tandy 1000 printer cable and check its orientation.[20]

Maintenance checklist

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  1. Check the rating label before connecting the mains.
  2. Unplug the machine before removing the cover.
  3. Remove dust from the supply, fan and drives.
  4. Inspect the supply and main board for leaking electrolytics, and the chassis for zinc whiskers.
  5. Check that the EEPROM at U17 is seated.
  6. Clean the floppy heads and check the drive select jumpers.
  7. Note the setup program's settings before changing DOS versions.
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References

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  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Tandy Corporation, Tandy 1000 SL/2 Installation and Operation, 1989, hosted as File:Tandy 1000 SL2 Installation and Operation Manual (1989).pdf. "Options for the Tandy 1000 SL/2", pp. 21-30.
  2. ↑ 2.0 2.1 2.2 "Tandy 1000", Wikipedia (retrieved 2026-10-21). Section "1000 SL and SL/2".
  3. ↑ 3.0 3.1 3.2 Radio Shack, computer catalogue RSC-20 (1989), p. 19, Tandy 1000 SL specifications, page scan at RadioShackCatalogs.com (retrieved 2026-10-22).
  4. ↑ Tandy Australia, computer catalogue no. 293 (1990-91), p. 4, Tandy 1000 SL/2 specifications, page scan at RadioShackCatalogs.com (retrieved 2026-10-22).
  5. ↑ Hayes, "Tandy 1000-series FAQ" (2005), section II.C.3, drive power cable colours.
  6. ↑ 6.0 6.1 6.2 6.3 "1000SL Err I/O of port 378h, not booting", Vintage Computer Federation forum, February 2021 to November 2024, thread. Posts by keenerb (18 February 2021) and Cloudschatze (16 November 2024).
  7. ↑ 7.0 7.1 7.2 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 and II.C.5.
  8. ↑ Hayes, "Tandy 1000-series FAQ" (2005), section II.A.1.
  9. ↑ Radio Shack, computer catalogue RSC-21 (1990), p. 17, "Intel math coprocessors", page scan at RadioShackCatalogs.com (retrieved 2026-10-22).
  10. ↑ Hayes, "Tandy 1000-series FAQ" (2005), section II.F.1.
  11. ↑ Hayes, "Tandy 1000-series FAQ" (2005), section IV.G.
  12. ↑ Hayes, "Tandy 1000-series FAQ" (2005), section III.E.2.
  13. ↑ Tandy 1000 SL/2 Installation and Operation (1989), "Troubleshooting", p. 35.
  14. ↑ 14.0 14.1 Hayes, "Tandy 1000-series FAQ" (2005), sections II.K.8, III.E.1 and III.F.2.
  15. ↑ Hayes, "Tandy 1000-series FAQ" (2005), section II.D.1.
  16. ↑ Hayes, "Tandy 1000-series FAQ" (2005), sections II.K.8 and III.A.2.
  17. ↑ Hayes, "Tandy 1000-series FAQ" (2005), section II.E.1.
  18. ↑ "Need help with Tandy 1000SL keyboard problem", Vintage Computer Federation forum, June 2024, thread. Post by keenerb, 8 June 2024.
  19. ↑ Hayes, "Tandy 1000-series FAQ" (2005), section II.B.5.
  20. ↑ Hayes, "Tandy 1000-series FAQ" (2005), section II.H.2.


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