Fixing a Radio Shack TRS-80 Model 1

This is a little description of the repair of a Radio Shack TRS-80 Model 1 for a Friend.

The computer comes with several problems.

  • Some IC are dead or in shorted state.
  • Keyboard flat cable.
  • One key “L” is dead.

Finding the cause of the fault has not been easy, i had to ask for a help to Ian, this dude is an expert of TRS-80 repairs.

How you can see from the photos, i had to replace a number of IC.

  • 4 x Video RAM 2102 (Z62 / Z63 / Z46 / Z48)
  • 1 x Z80 (Z40)
  • 1 X 74LS157 (Z31)
  • 1 X 74LS93 (Z32)

Stage of the defect (before and after):

Before repair After repair Replaced components


Keyboard repair (replacement of internal contacts):

Repair Keyboard Repair Keyboard Repair Keyboard


Micro Computer Technical Reference Handbook:

Download: TRS-80 Micro Computer Technical Reference Handbook (1254)

  1. Rob Clarke
    March 22nd, 2013 at 11:57 | #1

    Hi there, just looked at your interesting blog entry regarding repair of a TRS-80 model 1. I would be interested to know about your experiences repairing the key. I have a model-1 keyboard on which 4 keys are currently non operational and I was about to tackle them. Are the individual key’s easy to dismantle? What did you replace the contacts with or were you able to clean up the original contacts?

    ragards, Rob

  2. March 24th, 2013 at 00:49 | #2

    Hi Rob,

    Not easy to repair these keys, the better way is replace it with a spare parts, from other keyboard for example (with the same mechanism).

  3. Michael Weare
    February 5th, 2017 at 12:09 | #3

    Hello, recently acquired a TRS-80 model 1…works well apart from the space bar not working at all. Previous owner says it was working fine, but when I received it (well packed Aussie Post) space bar doesn’t work.

    How would I determine that the keyswitch itself is faulty. I’ll also need to put a meter on the ribbon cable to ensure that there are no issues there…they certainly look a bit frail. All other keys work fine.

    Appreciate your help.