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Tandy 1000 HD Capacitor Replacement Guide

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Tandy 1000 HD Tandon TM250 drive board silkscreen (Service Manual p. 3)
Tandon drive logic board. The electrolytics C11, C12, C17, C20, C28 and C39 to C43 are marked with their polarity.

Tandy's supplement for the Tandy 1000 HD publishes parts lists for three of its assemblies: the early HD main logic board, the 10 MB Tandon hard disk and the Western Digital WD1002S-WX2 controller.[1] It has no list for the power supply. See Capacitor Failure Symptoms for the signs of a failing part.

Power supply

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The HD's main assembly list names the supply board as "Outline PCB Power Supply (54w P.S. Stuffed)", part 8489073. The original Tandy 1000 supply is 8790070, and Tandy published its full parts list in the 1000 service manual; the HD supplement has none for 8489073.[2] The 8790070 values are in the Tandy 1000 guide. Check the number on your board: if it is 8790070 that list applies, and if it is not, read and record each capacitor's markings before ordering.

Early HD main logic board (PCB 8709556A)

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"Tandy 1001" main logic electrolytic and tantalum capacitors (pp. 32-33)
Ref Capacitance Rating Type as listed Tandy part no.
C13, C51, C82, C104 22 µF 16 V Axial 8316221
C26, C85A, C107 10 µF 16 V Axial 8316101
C101, C103 2.2 µF 16 V Axial electrolytic 8315221
C108 10 µF 10 V Radial tantalum 8336101
C124 100 µF 6.3 V Radial tantalum 8337100
"J14B-R81" 10 µF 25 V Non-polarised electrolytic 8396101

The positions and Tandy part numbers match the original 1000 board, but the HD list gives C108 as 10 V and C124 as 6.3 V where the 1000 list gives 16 V for both, so fit 16 V parts in either position.[3][4] The last line is printed with the location "J14B-R81", which is not a normal designator; J14 is the board's dual RCA phono jack. The HD board also lists a 0.25 A Pico fuse, F1.[3] Machines built on the cost-reduced 1000A board need the 1000A list.[5]

10 MB hard disk logic board

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10 MEG Fixed Drive polarised capacitors (p. 23)
Ref Capacitance Rating Type as listed Part no.
C11 10 µF 16 V Radial electrolytic CC-106MDAP
C12 1 µF 25 V Radial electrolytic CC-105MFAP
C17, C20 2.2 µF 50 V Radial electrolytic CC-225MJAP
C28 47 µF 16 V Radial electrolytic CC-476KDAP
C29 4.7 µF 16 V Radial tantalum CC-475MDTP
C39, C40, C41 22 µF 16 V Radial electrolytic CC-226MDAP
C43 4.7 µF 35 V Radial electrolytic CC-475MGAP
C44 0.47 µF 50 V Radial electrolytic CC-474MJAP

The rest of the drive board's capacitors are ceramic: chip capacitors and one radial 100 pF part (C42).[6] The drive's head and disk chamber is sealed; Tandon says it must not be opened.[7]

WD1002S-WX2 controller

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WD1002S-WX2 polarised capacitors (p. 27)
Ref Capacitance Rating Type as listed Part no.
C1 4.7 µF 15 V Tantalum CC475MDTA
C18 47 µF 35 V Not stated CC476MGAP
C19, C20 22 µF 10 V Not stated CC226JCAA
C32 10 µF 25 V Tantalum CC106MFTA
C33 1 µF 35 V Tantalum CC105KGTA

The list does not say whether C18, C19 and C20 are aluminium electrolytics; read the parts on the card.[8]

Procedure

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  1. Back up the hard disk and park the heads before removing the drive.
  2. Remove the controller by its single rear screw and lift it straight up; note the SW1 jumpers first.[9]
  3. Work on one board at a time, noting the polarity of every part before removing it.
  4. On the drive board, take care not to strain the connector to the sealed head and disk assembly.
  5. After reassembly, measure +12 V during drive spin-up and check the main board and supply as in Tandy 1000 HD General Maintenance.
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References

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  1. ↑ Radio Shack, Tandy 1000 HD Service Manual, catalogue no. 25-1001, Tandy Corporation, 1986, hosted as File:Tandy 1000 HD Service Manual (25-1001, 1986).pdf. Parts lists, pp. 23-33.
  2. ↑ Tandy 1000 HD Service Manual (25-1001), "Tandy 1001 Main Logic Main Assembly", p. 31.
  3. ↑ 3.0 3.1 Tandy 1000 HD Service Manual (25-1001), "Tandy 1001 Main Logic Sub Assembly", pp. 32-33.
  4. ↑ Radio Shack, Service Manual: Tandy 1000 Computer, catalogue no. 25-1000, 1985, hosted as File:Tandy 1000 Service Manual (25-1000, 1985).pdf. Main Logic parts list, pp. 94-96.
  5. ↑ Tandy 1000 HD Service Manual (25-1001), Introduction, p. 1.
  6. ↑ Tandy 1000 HD Service Manual (25-1001), "10 MEG Fixed Drive" parts list, p. 23; component layout, p. 3.
  7. ↑ Tandon Corporation, TM252 Rigid Disk Drive product specification, document 179050-001 Rev. B, section 3, reprinted in the Tandy 1000 HD Service Manual (25-1001).
  8. ↑ Tandy 1000 HD Service Manual (25-1001), "WD1002S-WX2" parts list, p. 27.
  9. ↑ "Adding a second (external) hard drive to the Tandy 1000HD", t1khd.txt, TVDog's Tandy 1000 archive (retrieved 2026-10-21).


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