Apple II+ Keyboard Problems

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Joined: Apr 5 2016
Posts: 32

Hi guys,

Been recently trying to also resurrect an Apple II+ from years gone by, and am stuck on the Keyboard.

Anyone have suggestions?

When I type various random keys like 12345 or QWERTY or 67890, I sometimes get the letter M in the mix. Happens randomly (once in a while) and doesn't matter the keys I hit. In addition, I do get a few "double" key hits on the letter T. Not sure if this is related or not.

Originally I had 14+ keys which didn't work at all, so I took the whole thing apart (see pictures) and did a solid cleaning. Now just the M key remains with problems (and the T) so I am close.

How do you troubleshoot? This model keyboard is not the older style switch type, is it even possible to use a multi-meter to test leads coming off the keyboard PCB? or should I test it at the encoder?

Most people have good examples of how to deal with older style keyboards, just not this type.

Any suggestions would be great.

Is this a keyboard problem or encoder?

I am excited to get this Apple II working, but the keyboard has frustrated me.

David

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speedyG's picture
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Joined: Nov 16 2011
Posts: 2377
Re: Apple II+ Keyboard Problems

Hello whynotpizza,

welcome to the community.

Just a point of logic:
the T key and the m key have no relation to each other.
You may therfor make the conclusion that it´s not related to the encoderchip.

It´s for sure that the problems are located at the keys themselves.

That keys are working with a steelspring contactblade.
So maybe the springsteel is just worn out a very little bit and maybe a very little affected by oxydation.
So i´d guess that careful cleaning of the contacts at the springsteel and bending it very slight little bit up wards
to tighten both contacts towards the PCB would solve the problems.

If you get "double keystrokes" it´s probably a problem related to the encoder.

That chip has a capacitor connected direct to 2 pins of the chip and that is
responsible for the so called "debouncing" of the keys. That capacitor might have been
struck by age and is fading slowly of it´s default value.
In such case it might be rquested to replace that capacitor.

But also in such case i´d recommend first to try and solve the problem by adjusting first the springsteel
contactplate.

sincerely
speedyG

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Joined: Apr 5 2016
Posts: 32
Re: Apple II+ Keyboard Problems

Hi speedyG,

Thanks for the reply.

I took the unit apart again tonight and tried a few of your suggestions (re-cleaned the gold contacts on the PCB board as well as very slightly bending upwards various contacts) and now the keyboard is slightly more messed up -- with other keys registering multiple or for other keys, and is still not working for the letter M. Last week when I was taking the keyboard apart and re-assembling, it seems I recall that the keys would do something different each time.

Hmm. Keyboard issue or encoder?

Earlier today I was able to purchase a replacement keyboard for the II+ which is supposed to be good and should hopefully solve that piece, but if I still have problems by swapping the whole keyboard out, where can someone get a replacement keyboard encoder board for the II+?

Attached are a few other pictures for more perspectives.

Did everyone else struggle with their old Apple gear, specifically around the keyboard?

David

speedyG's picture
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Joined: Nov 16 2011
Posts: 2377
Re: Apple II+ Keyboard Problems

Hello David,

the electrolytic capacitor is the wrong capacitor. It´s one of the small diskcapacitors.
I´d need a picture of the solderside of the encoderPCB.
In the meantime i indicated the realated pin.
The datasheet of the KR3600 encoderchip is availiable at my site at page:
http://www.appleii-box.de/D03_2_AppleIIKeyswitchesKeyboardsPage2.htm
Pay attention there are several datasheets of other encoder chips before you view the correct one !
You must scroll rather far down.
If you look for replacement please pay attention:
there are several versions of the KR3600 chips sold.
see the datasheet !

The bending was performed in a not very usefull manor....
You didn´t pay attention to the fact that the plates themselves must remain in parallel angle
and only violett marked contacts to be bent. I marked the contacts themselves in the scetch in light violett !
i add here some scetch for better explenation !
If you correct it should turn back to old state of problems
and maybe even solve the rremaining old problems themselves.

sincerely
speedyG

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In early days I had a lot of money but no time - now I have no money but a lot of time....
the second part includes less friends but a lot more joy on life....

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Joined: Apr 5 2016
Posts: 32
Re: Apple II+ Keyboard Problems

Ok, tried to bend the contacts properly this time (slightly upwards), but now when I plug the keyboard in and turn the machine on, nothing happens - screen is jumbled with lines and frozen. If I boot with the keyboard disconnected, the machine powers up ok.

So I thought maybe I bent too much, so I took it apart (again) and bent them back to the original state. Plugging in and turning on again, the machine won't boot.

I am in a keyboard la-la-land now! Smile

The design of this thing (in my opinion) leaves much to be desired. Not very serviceable.

Added a picture of the reverse side of the encoder board.

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Joined: Dec 20 2008
Posts: 203
Re: Apple II+ Keyboard Problems

Unfortunately, you've now probably plugged the keyboard connector in wrong and blown the chips. I did this before, it's an expensive mistake.

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Peter Rittwage
Apple II/II+ Registry - Register yours today!
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Joined: Apr 5 2016
Posts: 32
Re: Apple II+ Keyboard Problems

Possibly but I highly doubt it, since the ribbon cable seems to be permanently bent in such a way to make it difficult to plug in backwards. I am nearly 100% positive I did not plug in backwards.

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Joined: Dec 20 2008
Posts: 203
Re: Apple II+ Keyboard Problems

If the computer wouldn't power on with keyboard attached, you likely had it plugged in wrong. If not backwards, then off one pin which is just as bad...

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Peter Rittwage
Apple II/II+ Registry - Register yours today!
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speedyG's picture
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Posts: 2377
Re: Apple II+ Keyboard Problems

Hello whynotpizza,

in the picture below are the IC´s displayed that are related to the keyboard:

In case the plug was missaligned by shifting it from correct position 1 pin left or right
the most common damage is the killing of the 74LS04 at the encoderboard.
Repairing this chip is rather boring because it´s soldered and must be desoldered and this must be
doner very carefully avoiding to damage any traces at the PCB. If you have bad luck the 2 74LS00
chips must also become replaced. If you must replace any chip from the encoder board it´s a good idea
also to add sockets to the PCB so in case of future needs the task gets more easy.
The chip itself is rather cheap and easy to get from most electronic component shops
like for example in USA from Jameco.

Some times also the 74LS257 chips at position B6 or B7 on the mainboard get damaged too.
In more rare cases also the 74LS74 at position B10 might also be damaged.
these 3 chips are rather cheap and easy to get from regular electronic supplier
and they are rather easy to swap at the mainboard because that chips are placed in sockets.
sincerely
speedyG

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In early days I had a lot of money but no time - now I have no money but a lot of time....
the second part includes less friends but a lot more joy on life....

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Posts: 32
Re: Apple II+ Keyboard Problems

Thanks for the additional info, great detail on how the encoder board is setup!

Turns out this is not an encoder board issue at all.

I was able to score big the other day and pickup a brand new replacement Apple II+ keyboard (still in the box from Apple). It had been sitting on a shelf and was in top condition!

Anyway, when I connected it last night to my control board, the system booted OK, and ALL keys work properly on the board now!

This replacement keyboard is slightly different than mine (no weird "tin" back-plane underneath the keys), instead each is a micro-switch I believe, a much better design.

So I am up and running! Thanks for the help throughout the process. Smile

David