Atari 800 freezing and space bar issue

[bernie]

I have an Atari 800 that I purchased on CL and had to replace the CPU board on.

 

I have since discovered two issues:

 

1. It seems to randomly freeze and have some random characters appear on the screen for example when playing pacman. I think this may be either that my cartridge connection is finicky or that the cartridge cover gets a bit loose. Does anyone have any suggestions of what else to test or how to isolate?

 

2. My space bar is very finicky and only responds when I press the key in a particular location. Any guides or tips on what I should do to repair?

 

Thanks!

 

[ACML]

If you have a Hi Tek keyboard (white plungers under the keys) then I have a pretty good idea what's up with your space bar. The Hi Tek is an excellent mechanical keyboard, but it suffers a common flaw. The space bar takes a lot of punishment and the load (force) is transmitted to the printed circuit board (PCB). the solder post at location 57 de-bonds from the PCB and causes continuity issues. Since yours still works intermittently, the pin is mostly likely still there. Carefully remove the keyboard and look at location 57 on back. If you see a hole or the pin is still there and the solder pad is loose, resolder the pad. If the pin has fallen out (hole), the fix is a bit more difficult. You'll need to replace the pin and position matters. Using a multimeter, you'll have to hunt around for the right spot that still makes continuity between the two pins when you press the key. Then without moving it. resolder the pin. If you have the Stack pole (yellow plunger) or mitsumi, then I don't have any good ideas.

 

The freezing and random characters sounds like bad RAM. Re-position the three RAM boards and see if that helps. Remember, the OS card has to be up front closest to the keyboard.

Edited March 30, 2017 by ACML

[bernie]

Thanks.

 

I will try reseating the ram. From testing (before I put the case back on) I didn't really experience this issue, so I'm guessing that reseating may help.

 

Is this what you mean by white cap?

 

Do you have a picture of the back of the keyboard so that I know what I'm looking for? I've never taken apart (any) keyboard.

Edited March 30, 2017 by bernie

[Kyle22]

Look for cracks in the corners of those square white plungers.

[vattari]

Look for cracks in the corners of those square white plungers.

The front of the plunger does look like it's sheared away

 

 

Sent from my iPhone using Tapatalk

[ACML]

No need to disassemble the keyboard. The area I'm talking about is on the back of the keyboard assembly (see photo).