Help disassembling and reassembling late model II plus keyboard

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I have a II plus keyboard that does not use individual switches. It looks like the top is moulded plastic with shafts on springs and a contact board underneath. I hope that's correct from what I see as I not see individual key switches. I have misbehaving rows of keys (according to the schematics). Some rows don't work and others "bounce" once or twice. I have contacted the person I bought it from, but if the are not helpful I will need to take it apart and check for shorts or misalignments. Can anyone share tips and tricks for this kind of keyboard. It has to be a bigger pain than individual switches since everything must align.

I am also planning on trying an eye dropper with 91% IPL on each keyswitch pushing it 20-30 times before I try to dissemble. I know that helps on the individual keyswitch versions.

Thanks in advance...
Corey

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speedyG's picture
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Re: Help disassembling and reassembling late model II plus ...

Up till today i have never seen a keyboard within an apple II that does not contain single swithes... probably before giving any advise it can be usefull to upload a very "closeup photography" with at least some of the keycaps removed to get a detailed view of the keyboard at the "carrier-level" - usually all keyboards i have seen ( also from third party manufacturers ) were switches that had been "clipped" in a steelframe ( with the notches for the screws to fix it to the main steel carrier of the "groundplate" of the chassis - to be exact to the wrinkled and bent up two sideplates fixed to the "groundplate").... there might be a second problem beside the corrosion of the kays themselves inside.... in the meantime after 20 to 25 vears and the fact that the old solderingleads always contained a large part of lead - the lead itself starts - depending from the storingconditions - corroding..... so it might be usefull to resolder all solderingpoints at the backside adding some new solder..

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Re: Help disassembling and reassembling late model II plus ...


Well I cleaned the using a dropper and 91% IPA and spent a very long conference call mindlessly hitting keys over and over again.... According to my multi-meter everything looks OK now, but I will wait till the morning for all the IPA to evaporate just in case before I plug in my encoder and see if that fixes it.

I dread taking this thing apart since it looks like you need to know tricks or something to get it back together and aligned correctly.

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Re: Help disassembling and reassembling late model II plus ...

Just thinking, If it does work out to be the encoder, are their special flavors of the AY-5-3600? Would any one off ebay work? The actual encoder is a SMC KR3600-070BI, but there appears to be a bunch of flavors of this one (including the IIe version) and it is supposed to be pin compatible with the AY-5-3600 (the number listed in the II+ keyboard schematics).

Thanks,
Corey

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Re: Help disassembling and reassembling late model II plus ...

well after im able to see the photographs this looks very muck like some very early typ od capacitative based keyboard ( this means if key is pressed a plate is lowered and changes the capacitative value at the pressed crossoverpoint - but this is just a "looks like" - on the other hand the mentioned decoderchip is only used in mechanical keyboards with real mechanical switches - so to judge my first guess will stay at the mechanical keyboard.....

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Re: Help disassembling and reassembling late model II plus ...

in the meantime i´ve checked out my sparechip board but it only bears AY-5 1013 - and that is for sure the chip for german keyboards.... so i wish you good luck with the "simple method" hoping that the decoder is OK... i agree that the keys seem to be fixed with some kind of "snap-mechanic" to the top carrierboard..... the other point that seems cute by viewing the Photographs, is the fact that at bottomside of the keyboard is not the solderingside of the PCB - in other words: how can the keyboard work - if there are no keyswitches soldered to the PCB ? It looks more like the fact that the PCB is just fixed with the screws to the rest of the top part of the keyboard and that the entire keyboard might only be working under pressure to the upper part of the keyboard which can only be removed and assembled back in one entire part from and back to the bottom part. In this case the keys must bear inside of some kind of tube, a piece of foam and a small contact-plate and pressing the key generates a shortcut by pressing the contact-plate to contact 2 contact-areas on the PCB. So probably although it might be just be a try - it could be a good chance to untighten the screws a little bit and just lift the bottom PCB a little bit to take a close look from the side and try to verify if these thoughts are correct. In that case it might be possible just to take of the entire bottom-PCB-board and place it back after cleaning without to much difficulties....

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Re: Help disassembling and reassembling late model II plus ...

Well it's getting better....

I have done the IPL thing once with hitting the keys a lot....

I also re-did the solder joints at the connector (this is a terrible design as the connector feels like it will break the solder joints so I also used a glue gun to stabilize the connector to the PCB)

Now all the keys work except I have a bounce on 9 and I get a 0 when I press space and it looks like shift is on as I can get <> but not a period. Strange thing is when I use a continuity tester the space bar seems to be correct if I'm reading the schematic right (pin 10 and 2) and the shift is correct (23 and 24). I tried a different encoder (The Vince Briel one) and it seems to have the same behavior so I don't think it's the encoder.

Anyone have any ideas what could cause this?

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Re: Help disassembling and reassembling late model II plus ...

there was a thread just few days ago with some similar points....
one of the issues not on the keybord - but on the mainboard itself - is the timing of several chips related to the communication of the keyboard... there are some circuits that are located at (B6 = 74LS257 ), ( B7= 74LS257 ), ( B10 = 74LS74 ), ( C11 = 74LS04 ) and ( A12 = 74LS02 )..... - it might be part of the problem and up to my experience i prefer to make sure that all chips came up with same manufacturer ( preferably Texas Instruments ) and in some rare cases its usefull to exchange the LS-chips against F-chips that have faster timing ( espacially the 74LS74 and the LS04 and LS02 ) ...
the location marks (ie like B7 ) refer to the location matrix marks at the mainboard ( white numbering at the outside border of the board )...

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Re: Help disassembling and reassembling late model II plus ...

Could be a miss-match but I'm using the keyboard on a Mimeo Apple I. I guess I'll have to ask on the Apple I side if I can't figure this out later. Meanwhile I just did the eyedropper thing again and I'll let it sit till tomorrow to try it. The other thing i'm thinking is that there is some residual IPA and when I move the keyboard it is changing the matrix.

Thanks,
Corey

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Re: Help disassembling and reassembling late model II plus ...

in that case it make sense to request infos in the Apple I pages.... after all the logik from Apple 1 to Apple II did not change to much - but the layout was changed entirely so that of course the location marks are in this case useless.... but several people at the Apple I thread can give precise info to the correct location of that chips....
but i guess Mike Willegal tried to keep the choice of the used Chips as close as possible to the original Apple I....
- this means that no F-Typ chips have been used and it is advisory to the Mimeo to stay at that position...

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Re: Help disassembling and reassembling late model II plus ...

Think I figured out what is going on, now I have to fix it....

looks like pin 4 on the keyboard is shorted to the ground (pin 23) somewhere...

This messes with the shift and other encodes....

Unless I'm wrong and pin 4 is tied to ground because there isn't a numeric key pad.

Cheers,
Corey

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Re: Help disassembling and reassembling late model II plus ...

Well I reviewed the schematics and checked for shorts, apparently these keyboards are the opposite of the normal ones with switches. They get stuff stuck on and not that switches don't work.

Pin 4 and 23 should be shorted (sort of) if the bulb is in...

I have pin 13 and 16 always shorted "<-" back arrow
and pin 14 and 15 always shorted the letter "I"

Guess I'm cracking open the keyboard to see if the metal tabs are misaligned.

Cheers,
Corey

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Re: Help disassembling and reassembling late model II plus ...

I have a working keyboard!!!!!!

For future reference for anyone with this type of keyboard.

To disassemble remove the metal support bar screws, then start at the inside screws on the PCB then the outside and carefully lift up.
Take the plastic sheet and put aside... Clean with 91% IPL spray and a dust free towel.

Carefully check all keys and tabs. Rebend the supply tabs for the rows using a toothpick underneath to keey the shape and a small screwdriver to push down and re-create the "bow". I'm guessing they bend over time. One other thing I noticed was that some of the "bows" intentionally don't touch contacts and must be there to push the plastic in place so they don't short for some reason.

To re-assemble...
use toothpicks in the outer screwholes to help align everything.
Spray the PCB with 91% IPL and place and align the plastic sheet. This should hold it in place as you assemble with the PCB on top and the switch/metal tab area on the bottom. Don't assemble on a table you will push the switches down and mis-align. I found the best was was with my knees on the sides of the KB. Also as you start aligning keep lifting the PCB to make sure you don't snag a metal tab's top on the plastic as things slights move around.

Finally remove one toothpick at a time and assemble. Insert the outside screws that had toothpicks first, then all the inside then finally the metal support bar....

Grab a continuity tester and make sure nothing is shorted on the connector by checking every line for shorts, you can do this from the top solder joints or put the encoder back and use the pins.
Note: If the bulb is in you will have a short from 4 to 23.
If the encoder is in you may have shorts also between 20 and 23, 4 and 20, 21 and 3 (depending on the position of the reset switch)

The schematic really from "Understanding the Apple II" really helps to know if the short is should be there or not when you have the encoder card in.

One more thing what also complicated the situation was I had a stuck bit on my Apple II to Apple I keyboard adapter. I fixed the insulation by replacing one wire that wasn't touching when I first tested it for shorts but I must have bent it in a way that bit 6 and 7 were touching intermittently.

Cheers,
Corey

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Re: Help disassembling and reassembling late model II plus ...

Old thread.. but thanks muchly for spelling this out. Man, this is one complicated keyboard!

When you mention testing each of the solder joints or encoder pins for shorts.. you're testing each against the other, right (ie. 1 against 2, 1 against 3, etc?)

Also the pieces you suggest bending (I think you called them supply tabs).. is that the metal square tab itself, or the thing under it that acts like a spring?