Opening a 99/2

[+FarmerPotato]

I'm posting this here for the eBay seller. Please, add your own knowledge.

 

To open the 99/2:

 

First observe the bottom, metal side.

 

 

In the left and right edges, you should see metal clips engaging under some plastic tabs. There appear to be 4 metal clips on each side. On mine though, on each side, only two of the metal clips are engaged.

 

Now I flip the machine upright. I raise it about an inch off the table, grasping it with a hand on the left and a hand on the right. I bend one edge of the plastic case outward and put pressure on a key. Do this where each of the four metal clips are. Do it gently!  If you succeed, the bottom will begin to fall out.

 

Move to the other edge and repeat there.

 

Here it is when the last clip is disengaged. The rubber keyboard will stay put, but the plastic keyboard cover is loose. Lift the plastic case (and keyboard cover).

 

 

 

It's not necessary to remove the rubber keys. If you do, you will see a film underneath-- it's all guided into place by holes and pegs, not too complicated. But you don't have to disturb the keyboard. Above all, don't mess with the ribbon cable that connects the keyboard to the electronics.

 

 Just take pictures of the electronics.

 

 

Here are my inside photos:

 

 

          

 

 

 

 

 

To reassemble:

 

Notice that the keyboard cover has a lot of plastic pins. These will fit into holes. 

 

Place the top plastic cover lightly in place but don't press down yet. Make sure the keyboard cover is correctly placed and flush with the larger plastic at all edges. Making sure the pins are going into their holes.

 

Now press down and the metal clips should lock in place.

 

 

 

 

 

[matthew180]

What are the U5 and U8 ICs?  Admittedly I know very little about the 99/2.

[+mizapf]

One of them is the Video controller, the other is an I/O controller (keyboard, cassette, Hexbus).

[matthew180]

What are the actual part numbers?  Searching for any of those numbers is resulting in nothing related.

[Gary from OPA]

3 hours ago, matthew180 said:

What are the U5 and U8 ICs?  Admittedly I know very little about the 99/2.

they are basically custom chips, similar to how the 99/4 QI model had everything reduced to one controller chip for all the previous /4A glue logic.

[fabrice montupet]

Typically the kind of computer impossible to repair if one of these custom chips die...

 

Here is the I/O and Video ICs of my 99/2 early prototype:

 

 

 

 

[Gary from OPA]

56 minutes ago, fabrice montupet said:

Typically the kind of computer impossible to repair if one of these custom chips die...

 

Here is the I/O and Video ICs of my 99/2 early prototype:

 

 

 

 

 

Yes, hard to repair, unless we can find a pre-prototype, the engineer sample, see those red pin headers on both sides of the custom ic's, they would originally had a pcboard plugged in them, with a normal board make with 74ls chips and the AVDP, and the other one similar a bunch of 74ls chips, and the 9901 or similar chip.

 

If that model shows up, then people can reproduce the custom chips and document them how they work... Hopefully someday it does!

[+mizapf]

It may be possible (although I have no experience in that) to reconstruct the behavior from my MAME emulation of those two custom chips. I cannot really prove that I got their behavior by 100%, but sufficient enough so that the emulation works.

[matthew180]

When was the 99/2 produced?  Is there even any software available for it?  The little I could find online indicated it was intended to come before the 99/4A, but since it uses the 9995 I suspect, if it was complete, that it came after?

[+FarmerPotato]

I think the March 1983 99er reported it from the CES. Find the BYTE article too. It was intended as a low cost computer for teaching Basic, while the 99/8 would fill the high end. However the 4A price was cut to where there was no market position for the 99/2.