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Model I, Level II keyboard repair

sanchezman

Member
Joined
Aug 12, 2013
Messages
13
Location
Arizona/Michigan
So I recently had the incredibly good fortune to pick up a TRS-80, Model I, level II computer with manuals, cassette programs, and accessories for just $2 at a local electronics swap meet.

Everything about the computer works well. Everything, that is, except for the 'e' key. Pressing it does not register anything. I know that it is a problem with the switch inside, because by shorting the solder contacts behind the key, I can make the computer recognize a keypress. Incidentally, the 's' key also registers two presses for each time I press it, but that is easily remedied by deleting one of the s's.

Anyway, I was looking to examine the switch beneath the key to repair/replace it, but the switches are sandwiched between a metal plate and the circuit board. How can I get to the key in order to fix it? My electronic skills stop at crude soldering (and I lack a soldering iron), so if anything more than unscrewing/detaching is required, I will not be able to do it. If such steps are required, is there somebody in the United States who offers such services for a reasonable price?

It is a shame that such a wonderful unit is rendered virtually unusable because one of the most used letters in the English language is unavailable. I can't even make a simple program, because RETURN (RET.) requires the letter E.

Thanks in advance for any and all help.
 

Chromedome45

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Jul 6, 2009
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Central Florida
$2.00 lucky! I never have that kind of luck. :( Where was this anyway?

Ok onto trying to fix that key problem.

Take a paper clip one of the thick ones. Bend a tiny hook at the end. Place the hook under one end of the key cap in this case the "e" key and place your finger gently on the opposite side. This will keep it more centered as you pull up. May have to use a little force to get it to lift.

This should lift the key off the cap.

Look inside the key switch. If you see what looks like 2 metal fingers you can spray some WD-40 on the fingers and start pressing down on the key a few times.

Now power on the TRS-80 and see if the key registers. If it does than repeat for any other flakey keys. I have done this many times on my own Model 1.

Only valid if you have the older style keyboard.

Now if it is the updated keyboard than I beleive you may have to replace the switch. Or sometimes just reheat with a soldering iron to reflow the solder joints.

Either way good luck.;)
 

sanchezman

Member
Joined
Aug 12, 2013
Messages
13
Location
Arizona/Michigan
Thanks for your reply. The WD-40 worked on both keys. However, do you know the best way to reattach a key that snapped off the plastic cross thing that attaches it to the switch? I was a bit overzealous in my removal of the E key (I figured that if I couldn't get it off, it was as good as broken anyway).

I live in Arizona, and every third Sunday of the month, some local boy scouts run an electronics fair/swap meet. While the usual vendors offer some interesting things, it is the scouts themselves who have the best deals. They collect (lots of) old electronics from willing donors and sell them at the event. Anything they don't sell, gets recycled. Since the scouts don't need to make a profit, their items are ridiculously cheap. Normally, they don't offer much interesting stuff, but it is that "once in a blue moon" that makes me keep attending. If you thought I was lucky, my friend (who told me about this event) picked up TWO Apple ii+ computers, with software, documentation, hardware, and peripherals... for $5.
 

Chromedome45

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Central Florida
Darn I need to move to Arizona!

Anyway IMHO the best way might be some expoxy. Get the 1 or 5 minute loctite with the mixing tube at lowes. Usually sets in in about a few minutes. But don't pound on it for a few hours. Just don't use to much don't want it dripping down onto the key plunger or it might get glued as well. Super glue is good for something that is stationary. A key cap is not. That's just my 2 cents worth.
 

johny_2k

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Joined
Aug 21, 2013
Messages
36
I am glad you was successfull gettig the keys back to work withy a few spray of WD40. However, I heard that will bring lots of dust on the contacts.

I had to repair my Model 4 keyboard, but man, I got to remove all the key caps, desolder, disassembly the keys, clean up some, add conductive glue on anothers, test them with multimeter, solder everything again and finally assembly back the computer.
It was worth, the keys are working fine, so is the computer.

By the way, I got this on a blog just in case anyone's interested.
Roni.
 

Chromedome45

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Messages
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Location
Central Florida
If you don't use to much of the WD-40 and clean off the excess should be ok.

Johny_2k you most likely had the Alps keyboard. Those you do have to remov the key by desoldering 2 contacts and then gently pry open the
key switch after you get it out and slightly bend or clean the contacts. Had to do only one key on one of my model 1's and what a pain! Can't imagine doing all of them.
 

johny_2k

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Joined
Aug 21, 2013
Messages
36
If you don't use to much of the WD-40 and clean off the excess should be ok.

Johny_2k you most likely had the Alps keyboard. Those you do have to remov the key by desoldering 2 contacts and then gently pry open the
key switch after you get it out and slightly bend or clean the contacts. Had to do only one key on one of my model 1's and what a pain! Can't imagine doing all of them.

It was almost like you said... almost, because this keyboard has 4 soldered contacts for every key, not 2!!
And I have just noticed that I forgot one key: the up arrow. It is working only after pressing for a loooong time!
:)
 

johny_2k

Member
Joined
Aug 21, 2013
Messages
36
I have not, but if you do let us know.
I have also a model I level II but the keyboard came already working just fine, did not have to work on it.
 
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