Tandy TRS-80 Model 4

[Michael B. Brutman]

Tony Duell wrote:
> This sounds as thought it might be slightly differnt to my keyboard. I 
> only rememebr 2 contacts per key. On the other hand, when I ordered a 
> replacement keyswitch for my Model 3 (about 20 years ago), I did have to 
> specify the brand of the keyboard PCB (Radio shack apparently bought 
> these in). The keyboards in oth my M3 and M4 are ALPS brand, FWIW.
> 
> The reason I mention this is that dismantling the switches themselves 
> will vary between brands.

This is an ALPS keyboard.  Somebody at Erik's site mentioned that it is 
possible to coax a single keyswitch out of the unit by desoldering, 
squeezing some tabs near the top, and then lifting through the metal 
plate.  As things stand now it looks like I need at least 30 key switch 
mechanisms ..  it might be more practical to construct a replacement 
keyboard and hand wire it.

(I'm naively thinking some new Cherry switches, a sheet of plexiglass, 
and a lot of wire.  Not a pretty modification, but it gives me a new 
keyboard with switches that I can replace.  Has anybody done something 
like this recently?)

> I don;t know what drives you have (Tandon TM100s were fairly standard), 
> but if you take them significantly apart, you'll need an alignment disk 
> and 'scope when you come to put them back together. Again, something that 
> doesn't worry me _at all_ now, but it might be a problem for you.
> 
> If you want to take the drives apart to clean them, let me (us?) know the 
> model number (or any markings on them). I can then give you an idea what 
> what you can take off without losing the alignment.

Texas Peripherals 10-5355-001.  The inside of the case was fairly good, 
thanks to all of the extreme shielding that Tandy put in.  I cleaned the 
drive head and rails, and lubricated the rails with a teflon impregnated 
oil.  They are quieter now.

I'm not going to go much further than that without a scope and alignment 
disks.  If these drives go bad I have double sided drives from the PC 
family that I can use, or I will convert to use double density 720KB drives.


MIke