View Full Version : TRS-80 Model 1 Keyboard

April 29th, 2012, 06:21 PM
Can you debug a CPU board without the keyboard attached ?

My keyboard cable is poorly oxidized and is de-laminating.

Has anyone tried to upgrade this ?

I was thinking you could replace it with
a ribbon cable and a IDC connector on the PCB(s).

Ribbon cable has a small AWG, is it enough to
make a sufficient connection ?


April 29th, 2012, 10:59 PM
Mav, in Australia has replaced the ribbon cable with an IDE one. He wrote an article in TRS8BIT on how to do it. It's available as a free download at trs-80.org.uk

May 2nd, 2012, 06:39 PM
I converted my kybrd connector to IDE.

I'll post pic's when I'm finished.

Can anyone confirm if the TRS-80 Model 1 CPU
will boot normally with the keyboard disconnected ?

It's a PIA to work on the PCB with the keyboard
tethered to the CPU board.


May 2nd, 2012, 08:02 PM
Thanks for the mention Dusty. Yes, I am Mav.

Todd, if the computer is working properly you can power it up with the keyboard disconnected and it will display MEMORY SIZE? then some numbers which quickly scroll off the screen. When I'm repairing a M1 thats what I look for, then I proceed to attach the keyboard via an IDE cable and strip header.

Hope this helps.


May 4th, 2012, 06:14 PM
Here's a few pic's of my conversion.


Two keys don't respond, one will, if you tap it hard (sometimes get multiples)
and the other (break) does not. B4 I tear into the actual switch(s), any pointers
first so I don't destroy anything ?

May 5th, 2012, 12:58 AM
Those keyboards on the orangy-browny PCBs suffer from dry solder connections, have a look under your break key where it solders to the board. That's nearly always the reason for non-responsive keys on this type of keyboard.



May 6th, 2012, 04:19 PM

A few cold solder joint's touched up
and as good as new !

Thanks !

May 7th, 2012, 03:42 PM
Wow two out of two correct guesses! All of this stuff gets checked over on the refurbished Model 1s I sell, if people are wondering why I ask so much for them...


May 7th, 2012, 04:28 PM
I'm familiar with cold solder joints, I see them allot when
I work on 80's pins & vids. Normally it's due to over stressed

It never occurred to me...

But now that you mentioned it, the keys do
take a bit of pounding. I'll watch for it on
the next one I work on.