Atari 800 keyboard schematic

[Umberto]

Looking for Atari 800 keyboard schematic. I have some dead keys and need to trace down the open. I have eliminated the MB by substitution. Its the PC board with mechanical keys, no Mylar.

 

Thanks

Edited November 7, 2018 by Umberto

[Rybags]

https://www.atarimax.com/jindroush.atari.org/atkey.html

 

The Szebola schematic set is probably a better resource though.

800xl.zip

 

800.zip

 

The exact schematic shouldn't matter insofar as keyboard traces. The layout of the common keys is always the same.

The differences of course are the header pin assignments on different machines, no Help key on 400/800, 1200XL the only with F1-F4 by default.

 

Andas you'd probably know the console keys are independent of the matrix.

Edited November 7, 2018 by Rybags

[_The Doctor__]

???

use your meter and check each key, when you find a resistive one touch up solder joints, use a key puller on the 800 keys, or the shaft will split. pull the key cap off with tool and use de-oxit in or on the switch/leaf reassemble and use the key alot while still damp...

 

It will be fine, no need for all kinds of schematic work, which will just be a standard grid...

 

800 not 800XL correct? pretty much the same..

Edited November 7, 2018 by _The Doctor__

[Umberto]

I appreciate the response. Should have guessed that the array was the same as the other 8bits. I really haven't worked on the 800's that much, the one I have was my very first Atari and it has worked perfect since 1981 when I bought it new. The 800 i'm working on right now is a Frankenstein unit put together from two dead units I have acquired. One was a water damaged unit that has some sort of soapy material in it that corroded all the solder joints and most of the circuit board traces but the case is in almost perfect shape. The other one, has a messed up case but the MB is in perfect shape, just rebuilt the power board and it fired right up.

Every key on the 14th pin(on the mother board connector) is dead, but I have perfect continuity on every key, down the line, all the way to the motherboard. Its not the 4051's decoders because I can fire every dead character by jumping the keyboard connector pins on the motherboard. I'm probably missing something completely obvious but its getting late and I'm getting stupid. Anyways any suggestions would be appreciated, so I can have one of those "Doh" moments.

 

Thanks Rob

[Rybags]

The easy diag on the mux chips is to just swap them, if one is faulty then the key behaviour should change.

 

If you know a given line or two is suspicious the continuity test along it - I believe most have resistors ?

I do remember at least from the 400 that the header for the kb can accumulate a lot of oxide and crud so moving the ribbon up and down mutliple times can help there.

 

I do suspect the Pokey is probably fine - as it's using groups of 3 pins the send the row/column values during the scan, if one pin was faulty then it'd have affect on more rows than you're having problems with.