Atari 800 XL Repair Help?

[Nick Prince]

Short version: I replaced the 4051's, and the keyboard membrane and I still can't type, any advice on how to fix a keyboard with only silver/OS keys working?

Long version: 
 

Spoiler

Hello, I purchased a Atari 800 XL at a yard sale for 30$ years ago, the console was covered with a towel in the box along with 2 floppy drives, a printer, a modem, a touchpad, and 2 wireless controllers..

It sat for many years, I have it finally setup now I have only seen less then 10 random characters typed on it... I am unsure on how those characters showed up ngl..

I have always had major issues with the keyboard since I've purchased it, I have never been able to type a single letter purposefully, in the entirety of me having it.

When I purchased it years ago, I put it away in my collection and I have just taken it out of the box. 

The power cord originally worked initially when I first got it but after taking it out of the box after years it wasn't working correctly, giving me a waving screen with jumbled tiles. The Waving looked like something wasn't syncing with the TV, since I tried it on 3 different TV's and only 1 showed a reoccurring screen. 
      

I went out and got a new USB powercord, now the system functions* again like it used too, the test screen for the keyboard isn't green but slightly blue for some reason though.

The OS/Silver buttons work*, so I ran the tests and all the tests pass besides the keyboard... The test only activates the Option, Select, and Start button on the screen test.

I only have the carts if Basic, a Helicopter game cart, and a sio2sd tape emulator.. 

I only have been able to get into the Helicopter game, which works..


I have replaced the keyboard membrane because it looked like it had corrosion on it, I tried to clean it then bought a new one, I still have both. 

I replaced both the 4051's, I still have the original 2 as well..

I am unsure on what I can do from here..

Help would be apricated, I'm unsure if this is the correct forum though, if it's not please lmk, typing this was a bit long..

 

[StickJock]

Is the board socketed?  If so, try pulling out the POKEY chip and reseating it.  This will help to clean up any corrosion between the legs & the socket.

 

Edit:  Also make sure that the keyboard connector is clean & the contacts aren't bent.  I cleaned mine (on a 130XE) by using an index card.  I cut it to the right width, and then stuck it in & out of the connector until it stopped coming out dirty.

Edited January 6, 2022 by StickJock

[Nick Prince]

1 hour ago, StickJock said:

Is the board socketed?  If so, try pulling out the POKEY chip and reseating it.  This will help to clean up any corrosion between the legs & the socket.

 

Edit:  Also make sure that the keyboard connector is clean & the contacts aren't bent.  I cleaned mine (on a 130XE) by using an index card.  I cut it to the right width, and then stuck it in & out of the connector until it stopped coming out dirty.

It is socketed. I just pulled out the pokey chip, swapped it in iso with a qtip, nothing was on the qtip after a while, I did the same with the keyboard connector port/ribbon.. Still the same, only the silver buttons work..

 Long shot, @allpeople is there a point on the board that I can short that would cause letters to be inputted?

[StickJock]

Here's the keyboard matrix.

 

If you short a row & column pin together, you should get that key.  For example, shorting pins 5 & 13 together should produce an 'L'.

If this works, then the problem is upstream of the point that you are shorting the pins (presumably at the keyboard connector).  You can also try shorting the pins at the 4051s.

[Paul Westphal]

HA HA! Timing is everything!

I have done a TON of these and I'm stifled right now.( but do have answers )

I'm using the Retronics one.

This may apply to the Best Electronics one , but not sure.

Try using the original plastic insert over the one provided.

Try it without the plastic insert altogether.

Test the mylar without installing it and hit the buttons to make sure that it is operational.

I'm also going to try using both plastic inserts if none of the above yields any results.

 

This 800xl is fully socketed, and passed ALL Official Atari Testing Station tests before I even attempted this operation.

 

I reseated all of his chips.

 

I tried my own mechanical keyboard in his 800xl, and it worked.

 

I thought it was going to be a quick and dirty out the door job just like all the others but.. at one time when hitting the spacebar, it was resetting the computer ( while the real reset button still worked ) -WTF?

 

During all of this the side silver buttons all worked...

 

Also -try removing the RF shield - top and bottom - It may be shorting something out - run the board bare. I've done this many times.

 

I'm going to do all of my tricks tomorrow.

 

I'll keep checking in..

Edited January 6, 2022 by Paul Westphal

[+Nezgar]

Try swapping in a POKEY from another computer if possible...

[Paul Westphal]

This is with 2 keyboard plastic inserts. The original and the Retronics one.

This is without the ground wire for the keyboard. Not all motherboards had these. Most just had the cart port ground.

Next up I will try 2 mylars with the ground wire.

I thought halloween was over

 

I'm throwing the book at this today -Arrrrggg...

 

If anybody has any ideas - I'm game

 

Edited January 6, 2022 by Paul Westphal

[manterola]

I think is an excellent idea to first determine if the problem is in the keyboard part or in the computer. If it is in the computer and you have changed the Pokey and 4051s, a common cause of headaches are the old sockets.

It happened to me 3 times: changed a chip to repair and solve a problem, and suddently the computer does not boot-up or have another problem. Then I went pin by pin measuring continuity b/w the chip shoulder and the solder point in the bottom side of the PCB, and found connectivity problems in one or two pins.

[Paul Westphal]

As stated above, I have tried a mechanical keyboard in it and it worked fine.

 

I have reseated all the chips as well.

 

It also passed ALL Official Atari 8 bit Testing Station tests, which is not common these days.

 

I can touch up the solder points. Thanks!

[bfollowell]

I have two of Best Electronics new mylars and I've had trouble getting them to work after reassembling the keyboards. I've read of others that have said they've had to go back and loosen the screws a little bit after reassembling a mylar keyboard assembly. You know the machine works with a good mechanical keyboard, so that rules out the computer. If you've checked the mylar by itself and it seems good, you may have a similar issue.

 

[Paul Westphal]

You know what? I have used the Best Electronics ones many times and when they don't work the first time, I take out the inner plastic.

 

This is the first thing I tried with this Retronics mylar. No dice.

[djglish]

I had mentioned in another thread that not tightening the screws all of the way helped get my mylar replacement working.  Having the screws all of the way tight must have put the mylar connectors too close together.

 

[bfollowell]

2 hours ago, Paul Westphal said:

You know what? I have used the Best Electronics ones many times and when they don't work the first time, I take out the inner plastic.

 

This is the first thing I tried with this Retronics mylar. No dice.

 

1 hour ago, djglish said:

I had mentioned in another thread that not tightening the screws all of the way helped get my mylar replacement working.  Having the screws all of the way tight must have put the mylar connectors too close together.

 

 

I couldn't remember who had said that, but I definitely remembered having read it before. When I get the time to play with my 8-bits some more, I'll try loosening the screws a little. If that doesn't seem to help, I'll give removing the inner plastic a try.

 

[Paul Westphal]

I've been at this way to long. Good thing I opted not to charge him for the service after I realized how much trouble this was becoming. We try to save people dough when we can.

 

The video is the result of 1 mylar and loose screws.

 

Observations:

The feet of the mylar are almost TWICE the size of the original.

Also - The ribbon cable does not fit snug in the slot. There is room for it to slide lateraly in the slot. There might be 1 tooth's worth of lateral movement I can get out of the connection.

 

So I'm thinking the wide feet are shorting out on the connector. When looking at my connector I noticed his was not as wide as mine... that's why I almost tanked my Alps ribbon cable.. it scrunched the ends when I put it in his 800XL. ( it worked fine ). I had to do a delicate straighten and super glue to fix it.

 

I'm ready to just order a mylar from Best when I get more dough. I can at least get those to work.

I'll keep tinkering.

 

Keep throwing some ideas at me..

[_The Doctor__]

which mylar are you using and is the middle layer insulator sheet in there with the holes for the keypads lined up in the correct position?

can not see your mylars, the assembly, nothing, so we can't say based on just the keyboard and the ghost keys we see on the screen...

it looks like the traces are contacting each other shorting the matrix across keys...

 

that leave mylar shorting, or cable alignment issues...

Edited January 7, 2022 by _The Doctor__

[Paul Westphal]

I am using the Retronics mylar.

 

There's only one way the insert can go in.

 

I'd blame the Mobo if it wasn't for the fact that it passed all Supersalt Station tests.

 

 

 

 

Edited January 8, 2022 by Paul Westphal

[_The Doctor__]

the retronics mylars... do you have the isolation sheet in between the folded mylar? if the included one isn't there - that's an issue, if it is there but is too thin try use the original middle sheet from the bad mylar...  I wanted to see the mylar while it wasn't installed to see if the middle sheet was there and correct... look at it for possible defects... and to see the keyboard internals...

[Sugarland]

Have you tried the 'bad' keyboard on another machine to see what happens?

[Paul Westphal]

I replaced the 4051's and the pokey from my 100% perfect 600xl - No Joy.

 

Sugarlands idea was great but it too had the same problems on said 600xl.

 

I have the parts to assemble another keyboard so I'll put the mylar in that and give it a shot.

Edited January 8, 2022 by Paul Westphal

[_The Doctor__]

because it's not the machine... and we can't see the mylar or what you've done with it.

[_The Doctor__]

mylar with trace, insulating mylar with holes an no traces, that same mylar with traces folded over the insulator... it's a sandwich...

 can't follow you... 1 mylar, 2 mylar, etc.

 

If you would actually let people see the mylar with a stable clear picture , and the keyboard type from the side that connects to the mylar, there would be a chance of help and discovery. It's very clear that it's shorting in a few places...

 

If it works with another known good keyboard and the problem follows the keyboard your trying to fix... things are pretty evident....

 

nothing more to say or do... punching out of here...

[Paul Westphal]

Sometimes I meant insert when I said Mylar. I misstated. There is only one new Mylar, and two inserts. I have the original insert and the new retronics one. Apologies. I was frustrated when typing. 
Adios Doc - thank you

Edited January 8, 2022 by Paul Westphal