JGRAHAM2

Mine was different as well. I did the same as you and remapped it. I believe he had a note not to depend on the colors.

Looks like one was made in the US and the other in Taiwan. The US one had a darker shade on the Help key.

One did not have the plungers and the circuit boards were a different color. Of course someone could have replaced the keyboard with a fully populated XE keyboard....

One did not have the plungers and the circuit boards were a different color.

Looks like they sometimes used regular XE keyboards with all the function keys.

After cleaning it up, it looks like this. It was very crusty, like someone really used it, food crumbs and all. I think I’ll keep the badge as it is. A computer that was really used shouldn’t look like it just came from the factory.

The thing to remember is you have to choose to boot from your SIO connected device, the same as you choose to boot from the ram disk.

I used a dual dip switch and filed the existing toggle switch hole out to fit. I wanted to use my nibbler tool, but it it wouldn’t handle the thickness of the plastic. I haven’t secured it, but it is a press fit and seems secure enough as it is.

I bought this computer as a lot with some 1050s and a couple XLs from a guy’s son who inherited them. I wish I had asked what he did with them. I’m sure there is quite a story behind them. Two of them were upgraded with memory and the Expander OS that allows multiple RAM disks and to boot from one of them. Someone suggested a BBS in a post I have on this site.

It is the standard and the Expander OS. I have an XL with the same OS. I don’t know what he did with it. He had a very high socket of a type I’ve never seen for the OS. It looked to be high quality, but I couldn’t fit the 4 in 1 OS that I got from you under the keyboard. I removed it and replaced it with a precision socket. I had to add 4 bodge wires connecting to the BASIC ROM as I did damage the board removing it. (Works great, thanks!) It looks to me like this computer was wet at one time. See the picture of the lower shell. Posted a dump here:

What do you think he as doing on U21?

Has anyone seen this upgrade? Switchable from 128 to 512

I probably could now!

I like the discussion. There is a story to my first 400. I bought it at a Montgomery Wards warehouse store. I learned BASIC on the machine and how to fix it when I broke it. (Actually, a bar code reader called Oscar broke the SIO.) It got me started in an IT career. Now I work in the building where I bought it.

I can see your point, but this was what I wanted to do on my first computer in 1982. I tried to buy the keyboard, but couldn’t find one. I couldn’t afford the memory upgrade. It is a nostalgic thing.

By the way, the keyboard was made by Cherry. I was surprised at that.

Need to clean it up, but it works 100%! That little board to the left was to press on the four wires from the Mosaic board to the back of the cart port. I didn’t like that so I soldered them.

You are right. I was following the text when I soldered it and looked at the pictures when I checked it.

I found in another post on this site that you must use external power on S-Drive Max or FujiNet. I have both on the S Max and sure enough, it works!

So, after rechecking my soldering I confirmed the problem to be between the soldering iron and the chair. I had soldered wire “7” to pin 9 of the RAM chip instead of pin 8. Now it works with BASIC and other carts. It no longer works with the UNO cart. It also will not boot off of S-Drive Max OR FujiNet. PIA or Pokey?

Here it is Mosaic 48K RAM Upgrade.pdf

Thanks, I’ve never seen that before. I know the Mosaic documentation refers to it as a capacitor.

I have it working... kind of. Comes up as a black screen. If I hit reset, it will run a cartridge. It will even run the Uno cart. If I select a cart on the menu, it will start after another reset. Buck Rodgers will start without reset. Basic will produce a Ready prompt and will take input, but freezes after one line. It did all of this after I rotated the RAM chips. I believe it’s just a bad chip.

One thing I notice is one of the solder points goes to a diode on this board. It is a resister on my other 16K board. (C523)

I appreciate the offer, but I have installed the Mosaic and right now, it isn’t working right. I’ll be troubleshooting it tonight.