Hey guys,
I am an old school apple II guy who recently decided to buy some old machines (used the library machines when I was a kid, couldn't afford them), but my apple //e platinum is having some keyboard issues. I am hoping to get some insight or assistance troubleshooting it.
My "2 w d x c" keys do not work. I have a suspicion that it is the UE14 IC (in this case a KR9600-PRO), but I can't really be sure. C70 looks ok, but who can say. I think that would only cause issues with timing anyway, not a group of keys never working at all.
1) Is there a way to determine if its the keys or the decoder (maybe with an ohm meter?) with any certainty?
2) Could it be something else?
3) Where can I get a replacement keyboard decoder, if I need to replace it?
Kevin
hello kevin,
under normal circumstances it´s not the decoder at the 2e.... the decoder is mostly damaged at the II or the II+ because if that keyboard cable to the mainboard is plugged in wrong way the powersource hits the wrong lines...
at the IIe the cable containes mostly only the lines from the keyboardmatrix.....
so mostly in this cases the issues are by bad switches or bad matrixlines of the keyboard.....
its easy to decide which problem is yours... if all keys belong to one matrixline its the line to be examined... your case seem to match with this case ...( vertical matrixline 2,w,d,x )
if the keys belong to different matrix lines its the keyswitches themselves.... ( that would match to the c-switch )
usual issues are, dirt in the switches, bad solderingpads due to age or corroded lead.....
if you have the circuitplan and a multimeter you can unplug the keyboard from the mainboard and measure from plug to the keys the lines for interruptions ( i.e. no contact at all ) that cause the matrixline to fail....
and you might also measure - if the keyboard is unplugged the function of the keys themselves with proof of shortcut ( key pressed down ) or no shortcut ( key released ).
here are several threads here where detailed cleaning procedures for the keyswitches themselves have been explained....
if corroded laed is the problem then resoldering is the solution to the issue...
sincerely speedyG
Yep, just trace out the bad key's lines. Look for cracked solder pads. Right where the trace enters the round pad area. You can do this without a schematic. Be aware the the traces may go through other keys, so you want to start at the suspect key (each one of the failures) and work back to the connector. Inspect each joint and pad area. A DMM helps, but is not required for this part of the troubleshooting. Believe it or not!
The Platinum keyboards have had too much cost cutting, no reinforcement. They couldn't take the banging by kids as well as the prior models could.
Ok, so this appears to be the layout of my //e platinum keyboard: http://www.applefritter.com/node/7257.
When testing from continuity from the keys to the cable end:
Key----Switch #------pad 1---------pad 2
2---------------3---------14-------N/C (4)
W-------------18---------18-------N/C (4)
D--------------33---------16------------2 (seems to work, doesn't type though...might be dirt)
X--------------45---------20-------N/C (2)
C--------------46---------20-------N/C (4)
So the 2 W X keys all run on pin 4 of the keyboard connector, but don't work, however, S (switch 32) DOES work.
The D and X keys run to pin 2 of the keyboard connector, and although D tests for continuity, it doesn't work.
Looking at the board layout, it appears that all of the non working keys pass very close to switch 33's position,
but they all don't touch switch 33s contacts.
There was some yellow colored resinish(probably flux) stuff surrounding the area of 33 and its neighboring switches,
but alcohol and a little pressure seemed to remove it. There were no changes in continuity after it was cleaned from the board.
I don't see any broken or cold solder joints from inspection.
As Speedy suggested, it appears that the keyboard itself is an issue. If the decoder is bad...its also getting bad data from the keyboard as well.
Any ideas? Should I just resolder the pins of the switches that aren't working? I can't trace the lines, it makes me
crosseyed before I get more than 3" away, even trying to use my meter probe as a vantage point...
Kevin
hello kevin,
as explained each single switch itsef can be tested if the keyboard is unplugged from the mainboard - otherwise internal parts of the decoder make measurements faking to you ...
each key is just nothing else but e switch so you could even test the keys with very simple material:
+ 6 volt battery----wire ----6 volt lamp from bycicle ( light on or off ) other pole of lamp ---- wirepoint
key pole - key pole ---- other wirepoint - wire -- minus pole of battery....
if connection between keypole and second keypole is closed the lamp will ignite light if the contact remains open the lamp can´t show light.....
its just go or no go....
if the keyswitch works correct the connection is closed when the key is pressed and it must be open when the key is released...
another commen reason for malfunction is caused by spill of drinks like coke or coffee in the keyboard...
the keys with malfunction are close together and this could turn out to be the "bad-boy".....
i don´t remember exactly the correct thread - but there is one with very detail description of opening the switches and cleaning them and putting them together again.... probably you might find it with the "search" function and the phrase "cleaning the keyswitch" or similar.... the time since that thread was issued is at least 6 months or more....
edit: i found it - the thread is from corey986 "Help disassembling and reassembling late model II plus keyboard "
end of edit
and as far as i remember is was related to a Apple II+ keyboard... but the switches are similar and the cleaning procedure is similar too....
if you have a solderingiron it is surely a good idea to resolder the points because coke and coffee cause solderinglead to corode and you might not be able to view that just from outside view... but resoldering and adding a little new soldering lead solves that issue...
that would be the simple solution ... the tough task will be to clean the keyswitches inside.... or to replace them with keyswitches from another damaged keyboard with correct-working keys from there...
a replacement of the keyboard decoder only makes sense if all keys have been checked out to work correct and still a mistake remaining....
sincerely speedyG
I have a decent hakko iron, I'll see what I can do. I don't think I'll worry about a replacing the decoder until I know the kb is good.
I won't worry about pulling the switches apart unless the solder job doesn't work out, but I'm going to go through the thread either way...
Thanks Speedy!
I'm not sure if my old post will help. The late model II plus RFI keyboards did not have individual switches but had a sandwich kind of design with a PCB and a metal frame to make key contacts and a plastic cover with sprigged plungers to push the metal frame.
Before taking out the soldering iron and risk melting the insides of switches...
If the IIe has separate switches, I would suggest reviewing Mike Willegal's site (willegal.net) on keyboard repair. But basically ISP in an eye dropper and a lot of spare time can revive a lot of switches. I think I have saved about 50 or 60 datanetics switches this way and only had about 15 out of 2 keyboards worth that needed real replacement.
Good Luck...
Cheers,
Corey
just to complete the mail of corey986 the link to the mentioned page is:
http://www.willegal.net/appleii/appleii-keyboard.htm
.....
hello corey986,
this thread again indicates to me that those of us, that are more common with repair tasks, should pick up again a idea that has been published here several times to discuss with Tom Owad.... :
it realy turns out to be a good idea to create some kind of DIY-help-pages with some kind of hierarchic structure like this:
computertyp - computermodel - mainboard/paripherial - partname - subpartname - referencepage
i.e.
Apple - AppleII - keyboard - keyboardpcb - keyswitches - decoder - related capacitors
and filling the stuctures with pages illustrated by pictures and repair in detail...
at the end of the next week my recovery from the surgery will be continued that far that i´m permitted to stay for longer time without the bondage fixing the left arm to the body and i intended anyhow to continue my own thread "hardware and special topics" and it seems to be a good idea to add this on the todo-list in the next 3 or 4 months to make an example-page how such a reference page might look alike by making a page with explosion-drawings of the common different types of keyswitches used in the applekeyboards and how to open and close them again and explaining the way how they work....