Atari 800XL keyboard inop except silver buttons

[bytebinge]

I recently refurbished and upgraded this 800xl and was excited to put it back together. Turns out the keyboard does not recognize the majority of the keyboard keys, only the silver buttons on the right side (reset, options, select, etc). 

 

I swapped the keyboard: same result.

I swapped the Pokey chip: same result.

 

Does anybody have any troubleshooting advice? 

[bytebinge]

It was this U24 chip. It was corroded. Cleaned and replaced...guess I should remove every IC and clean....

[+Stephen]

Nice job bringing one back.  Thanks for sharing the resolution.  So many people ask a question, but never share the answer!

[Beeblebrox]

Yup, I fixed a 600xl the other day that exhibited exactly the same. This time it was the 4051s themselves. Replaced both 4051s and all keys came back. 

 

With XL and XE keyboards (excluding the 1200XL), it's generally one or more of the following :

 

-Bad mylar (if a mylar/membrane keyboard) if whole rows on the same matrix aren't responding. Either damaged/cracked/oxidised or dirty mylars. Either fix, clean or replace. 

-Bad 4041s if random keys don't work but others work next to each other in the same matrix. Replace chips

As illustrated above also sockets for these chips can clearly cause issues. 

-Bad key switches if the odd key doesn't work on mechanical condition switch types

-Cold solder points for mechanical switch types.. Reflow solder. 

-In XEs with some function keys not responding and the mylar is ok, if applicable there is a resistor fix you can use. (Can't recall the exact explanation but it think it's something to do with a resistance overtime with the circuit and or mylar that stops the signals getting through, and adding resistors helps). 

-Failing pokey or pia chips - swapping out (if poss) into another A8 will see if these are the culprits. 

 

-For some XL mechanical switch type keyboards sometimes keys which haven't been used for decades can simply be brought back to life by repeatidly pressing them 50 to 100+ times. 

 

-For the 800 computers it depends on if you had a stack pole or hitech post style. Here non responsive keys can be bad switches, bad solder points. Reflow solder. Sticking keys can be cracked posts collars. There is a rubber o-ring method fix or a 3d printed version, but it depends on whether stack pole or hitek. 

 

-The other type of mylar (mitsumi made) based keyboards which you get with all 1200xls and occasionally, if you are lucky, on some 800s,  exhibits failure due to a build up of residue on the fingers of the pcb that connect with the mylar. Fjc has a video that shows how to fix these. I've fixed several 1200xls and one 800 this way. Relatively easy and straightforward. 

 

Alternately best electronics sells a kit for it. Personally the DIY costs nothing and might take an hour. 

 

The 800xl and 600xl keyboards are interchangeable between the two machines, although because there are 4 or 5 types, some mechanical switched and some mylar, what I've noticed is that where you have a heavily upgraded machine with lots of upgrades like u1mb, VBXE, stereo, etc, sometimes the top casing won't close. Especially on a heavily upgraded 600xl. Here, the mylar keyboards with the metal backplate are usually an issue. Swap em out for one which is mechanical with a pcb and you get more clearance. Just make sure nothing is shorting. 

 

Sorry, realised I've somewhat hijacked this topic, but it's all related.

 

Edited December 21, 2023 by Beeblebrox

[bytebinge]

Interesting point about some of the keyboards being interchangable but possibly not fitting correctly, due to various types. I actually swapped this refurbished/upgraded 800XL keyboard for a spare I had from another unit, because the keys bounce back better. 

 

This was my first Atari 8 bit system restore project. Got it inop on Ebay: recapped, swapped RAM, installed UAV board from Brewing Academy, and last step turned out to be removing and cleaning all the ICs. I did not know to look for "Made in Hong Kong" when I got this, so I got lucky on all ICs being socketed. 

 

I opted to not do the 1mb memory upgrade. I don't care about all the OS options and such. If I really want to play programs with higher RAM memory needs, there is an upgrade kit that just plugs into the parallel port. I guess there is some Atari XE and XEGS SW content that can be accessed through such an upgrade, but the 1mb upgrade seems too troublesome, with not much additional game options for that extra effort, when I can just slap in a memory upgrade to the back port and access XE AND XEGS dev content. 

[Beeblebrox]

Yup, Hong Kong made = fully socketed.

 

U1mb is a pretty easy install, especially for a fully socketed machine. 

 

Just out of interest you rarely need to recap an A8. I've fixed many many a8s and only had to replace 1 x cap in one machine. The A8s seem very resilient in that respect. 

 

BTW there is an existing thread on as about the various 800XL and 600XL keyboards:

 

 

Generally Alps made ones are great, as is one of the awc ones. Some are awful and impossible to comfortably type on. 

Edited December 21, 2023 by Beeblebrox

[bytebinge]

I will check out this keyboard thread. 

 

I'm am genuinely interested to hear your take on why 1mb of memory is valuable. I sincerely couldn't find anything other than "Atari Blast" and "Space Harrier". I only care about games, not visual demos or whatnot. 

[Beeblebrox]

Ah, well I love demos. The 1MB Rewind demo is amazing. 

 

Tbh it's not so much about the full 1mb.

 

For example for me, if u1mb costs £80, and a rambo xl 256k up costs me say £30 by the time you buy the board and ram chips, the cost for u1mb is IMHO justified because:

 

-U1mb has built in spartados x with battery back out real time clock. 

-It gives side3 full atr support with a PBI hard disk drive

-Has plugins which allow me to control, for example, my Sophia 2 and stereo configs

-Is actually easier to install than some stand alone ram only upgrades. I've installed countless rambo xl boards in mostly non socketed 800xls. You have to remove all the ram chips, install sockets, socket the 74ls158 chip and the pia. U1mb requries sockets for 2 x chips and 4 x wire connections. 

-Flashable os rom slots 

 

It's not for everyone but again it's not about just having 1mb of ram. Because as you say not much software out there uses 1mb.

 

The good thing is there are loads of ram upgrade options, both internal and external. 

 

Like with anything to do with retro computing it pays to read up and do your research, then go for what best suits you. 

 

 

Edited December 21, 2023 by Beeblebrox