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A couple of Texas Instruments TI-99/4A Home Computer repaired

I have repaired nine motherboards of the Home Computer Texas Instruments TI-99/4A for a dear friend. Below the description of each repair.

Texas Instruments TI-99/4A Repair (1 of 9)

Defect:

  • Blue Screen with tiny Vertical lines and deafening sound … and then garbage screen.

Replaced parts:

  • 1 x 1501392-27 ROM (U611)
  • 2 x 4116 RAM (U102 / U105)
  • 1 x 74LS245 OCTAL BUS TRANSCEIVER (U614)
  • 1 x 74LS03 QUAD 2-INPUT NAND GATE (U506)

Texas Instruments TI-99/4A Repair (2 of 9)

Defect:

  • Blue Screen with tiny Vertical lines and deafening sound.

Replaced parts:

  • 1 x CD3227A ROM (U611)
  • 1 x CD3226A ROM (U610)

Texas Instruments TI-99/4A Repair (3 of 9)

Defect:

  • Garbage Screen.

Replaced parts:

  • 4 x 4116 RAM (U105 / U106 / U108 / U109)

Texas Instruments TI-99/4A Repair (4 of 9)

Defect:

  • Blue Screen with tiny Vertical lines and deafening sound.

Replaced parts:

  • 1 x MCM 6810P RAM 128×8 (U609)

Texas Instruments TI-99/4A Repair (5 of 9)

Defect:

  • Blue Screen with tiny Vertical lines and deafening sound.

Replaced parts:

  • 1 x MCM 6810P RAM 128×8 (U608)
  • 1 x 1501392-27 ROM (U611)
  • 1 x 74LS138 1-OF-8 DECODER/DEMULTIPLEXER (U504)

Texas Instruments TI-99/4A Repair (6 of 9)

Defect:

  • Blue Screen with tiny Vertical lines and deafening sound.

Replaced parts:

  • 1 x CD3226A ROM (U610)
  • 1 x 74LS138 1-OF-8 DECODER/DEMULTIPLEXER (U504)

Texas Instruments TI-99/4A Repair (7 of 9)

Defect:

  • Blue Screen with tiny Vertical lines and deafening sound.

Replaced parts:

  • 1 x TMS 9900-NL CPU (U600)

What happened to the other two motherboards ?

  • The eighth motherboard was used for spare parts.
  • The ninth motherboard has all components burned (Power Supply problem?)

  1. fedepede04
    January 18th, 2015 at 18:56 | #1

    I do envy you a little when it come to your skills in repairing of retro stuff

  2. fedepede04
    January 18th, 2015 at 18:57 | #2

    keep it comming :)

  3. METTA ROBERTO
    February 18th, 2015 at 10:12 | #3

    HO UN ESPANSIONE MEMORY 32 K PER IL TI 99 NON FUNZIONANTE

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