Apple II+ character ROM

[Arn_K]

Hi everyone,

Yesterday I bought an Apple II plus, it is a European model, but the label is for a regular plus, not the europlus. Possibly an early model?

But unfortunately, it is missing the character ROM. It is a rev 4 board, so it uses a 2513 ROM instead of a 2716 like in later models.
I have tried to use a 2513 from my apple I replica, and it does show some signs of life. I can blind type a basic program and that seems to work,
but the characters are wrong because I think the character set is different.

I did find an 2513 to 2716 adapter on GitHub, But I'm not sure if this could work.

GitHub - bbenchoff/2513CharGenAdapter

Contribute to bbenchoff/2513CharGenAdapter development by creating an account on GitHub.

github.com

I need some advice what to do next, is it best to buy an original character generator or possibly make an adapter, so I can use a 2716?

 

[nijssen]

I created a Character Generator Tester (see https://8bitflux.com/#character-generator-tester).

I could not see a different in font between a Signetics 2513 IC from 1977 and a RO-3-2513 chip from 1979, the first can be used in an Apple 1 and the second I have in my ITT 2020 (should be the same as early revision Apple ][ I suppose). So I am curious why you say the character set is different, do you have any pictures?

Maybe the schematics of my tester are of any help to you as well.

Edit: I attached a picture for clarification, I referred to the IC in the bottom left and the right.

View attachment char-generators-examples.JPG

 

[dorkbert]

AFAIK, the EuroPlus are made in Ireland. A EuroPlus should also have a modified logic board (a few jumpers change)
If your logic board does not have those changes, it's possible you have a stock II Plus fitted with a EuroPlus lid.

 

[nijssen]

The EuroPlus came with an 2316B character generator (top left in the picture I posted earlier). Dorkbert is correct that the EuroPlus has modifications on the board. Some pictures of the problem Arn_K has would clarify things.

 

[Arn_K]

I have attached some photos of the Apple ][+

Isn't made in the USA, and the label just says "Apple ][ plus" not "Apple ][ europlus". And the power supply is a 230v only model.
So I'm not sure what happened to this Apple II, maybe it was made in the US and adapted for the European market before the europlus was made of mabye to meet demand for the europlus?
Or maybe someone just made an apple II from spare parts.

There is also a photo of the video output. This is what I get with the apple 1 character generator. There seem to be characters display at the correct position on the screen, but it's displaying the wrong characters.
For example, a blank space has been replaced by an `

I thought the 2513 was basically a masked ROM. And I think the content of the apple 1 ROM is different from the apple II version.
That is why I wanted to replace the original 2513 mask ROM with a UV erasable 2716 if possible.

The motherboard is a rev 4 version.

 

[nijssen]

Strange behavior indeed. I doubt your ROM to be an Apple 1 character generator. It shows characters that are not in an original 2513, like the arrow pointing to the right, or the `. For example, the apostrof sign is a three pixel completely vertical character for the Apple 1.

I think an adapter for an 2716 (like the one you pointed out) would work, never tried it though. Make sure to double check voltages before insertion. The 2513 uses +5V, -5V and -12V, while the 2716 only makes use of +5V.

 

[Wayne Stewart]

Reactivemicro has these

Apple II/+ 2513 Character ROM, Apple PN: 341-0036

The 2513 Character ROM was also used in many other computer and terminal systems from the period.

www.reactivemicro.com

 

[Arn_K]

Thanks for the tip, but I believe Reactivemicro is based in the US, and I am in Europe (Netherlands).
So the shipping cost and import cost will result in a grand total of about €100 to €150.

So I want to try the EPROM adapter, if that doesn't work then I will buy an original 2513.
But still, thanks for the tip.

I'm not sure what could be the issue with the apple 1 character generator. I got the chip with the empty clone motherboard, but I never finished that project.
I'll get to it someday...

I have ordered the PCB's for the EPROM adapter. I'll send an update if they work (or not) when they arrive.