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2 x Texas Instruments TI-99/4a Repair

Texas Instruments TI-99-4A Repair #1

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

Defect:

  • Wave/Raster Lines.

Replaced parts:

  • 1 x Variable Inductor 2 -> 4.5 μH (L100).

Gallery of repair:

 

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

I should point out that someone has already tried to repair, without success.

Defects:

  • Black Screen (no raster, no sync) short circuit between 12v and 5v . . . and then . . .
  • Wave/Raster Lines.
  • Blue Screen with tiny Vertical lines and deafening sound.
  • Garbage Screen.

Short Circuit Note:

  • The short circuit was due to a malfunction of the IC: TIM9904ANL (U601)

Replaced parts:

  • 1 x Variable Inductor 2 -> 4.5 μH (L100).
  • 1 x TIM9904ANL (U601)
  • 2 x MCM 6810P RAM 128×8 (U608 – U609)
  • 1 x 74LS245 (U614)
  • 1 x TMS9929 (U100)

Gallery of the repair:

  1. nameles
    September 9th, 2017 at 18:38 | #1

    Hi !
    Where I can buy this capacitor C101 12pF
    I have only a small. I dont know how search it

  2. September 9th, 2017 at 18:50 | #2

    @nameles

    Hi Nameles, i have wrong to write in both repairs (now correct) this is a Variable Inductor 2 -> 4.5 μH (L100), you can choose the right one on this range.

  3. nameless
    September 9th, 2017 at 20:00 | #5

    Great !
    I havent got a 3.3uH but I have only 10uH and I connect inductors in parallel.

    Another TI-99/4a comes back to live.

    THX !

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