Atari 64K 400/800 Card CA061435 ?

[KLund1]

I found this with other 16K cards.

Is this the card that would have come with the 400 48K upgrade kit pictured? The box is empty so I can't check.

Or is this some other unknown card? I did a google search for the Atari part number and got only one hit for a thread in here.

[+kheller2]

What the difference between this card and CAO61553 ?

[Paul Westphal]

Yes that card goes with the box. Best Electronics has them for $25.

[KLund1]

kheller2 I do not know.

Paul, Many thanks!

[ClausB]

Your board differs slightly from the 400 48K board I documented in the thread below. So I'm not sure it would work in a 400. Could you post a photograph of the reverse side of the board?

 

http://atariage.com/forums/topic/185500-using-the-atari-400-48k-board-in-the-800/?do=findComment&comment=2335665

[KLund1]

I have a working 16K 400. I put the jumpers on the back of the 400 MB according to the 48K upgrade kit instructions, and fired this up. It did not work. Just a blank screen.

I swapped out the 74xx128 IC's from the working 16K just to check, still blank screen.

Here is a picture of the back.

Also the color of the PCB is much lighter green color them all other Atari 400/800 cards I have seem.

I was told this was from a Atari research engineer. He had many unusual items. And I am working through them.

 

[ACML]

I have this same board and always assumed it was the official Atari 48K upgrade board that goes in that box. What else could it be?

Edited July 9, 2017 by ACML

[KLund1]

I have the one from the box working and installed in a 400. I'll dig it out and open it up and take a look.

If they are the same, then this pictured card is bad. If different, the sky's the limit of 64K...

[ClausB]

Thanks for the photos. I'll try to trace the circuit to figure it out. At first glace, it's similar to the CO61550 but it is missing the 74LS32 chip that handles the cart select signals for access to RAM above 32K. I think it could be made to work in an 800 at least.

[+kheller2]

Going through the master item list found this:

 

CA061434 PCB SUB-ASSY - 64K RAM REV B

CA061435 PCB ASSEMBLY - 64K RAM REV A

CAO61552 PCB SUB-ASSY - 64K RAM REV A

CAO61553 PCB ASSEMBLY - 64K RAM REV A

CO61550 P.C.BOARD (FAB) - 64K RAM REV A

CO61551 SCHEMATIC, 64K RAM CARD REV A

CO61559 P.C.BOARD (FAB) 64K RAM ADAPTER REV A

[KLund1]

This top card is the one in question. the bottom card is from the 48K Expansion kit box above. The board layout is different, as is the part number.
I put int board in question into this second 48K working 400, and it still did not work. Just for kicks I put in an 800 only the OS card and got nothing.

Then I did some 'one at time' chip swapping. All socketed chips worked in the working 48K board. So one of the soldered IC is bad, possible but unlikely, or this board needs other changes to the MB to work correctly.

Any other thoughts about this board?

[+kheller2]

Have pics of the solder side as well? 1553 looks like a later design with an additional support chip.

[ClausB]

The lower board is the one I posted a schematic for in my link above. The upper board is very similar except for the LS32, as I mentioned above. Give me a few days to trace the circuit in your photos.

 

I have a suspicion it might work as a 32K board in an 800. Try it in slot 2 with a 16K board in slot 1 (and the OS board in slot 0 of course).

[ClausB]

Oh I think I see it now. It is a 48K board for slot 2 of the 800 but it needs a loopback board in slot 1, which would connect pins 18 and P together and pins U and M together. Can you find such a board in your collection?

[ClausB]

The loopback board would probably be smaller, with no chips on it, just those connections.

[KLund1]

I just tested with a 16K in slot 1, then the 64K board. and the 800 Booted!!

So it is a 32k Board But with 64K chips. would the other 32K be bank switchable? Seems a waste to just loose/forget the other 32K

[ClausB]

OK but I still think it's a 48K board as I posted above. Have you looked for a loopback board?

 

If you can't find it I could come up with a simple board mod to work without it.

Edited July 13, 2017 by ClausB

[KLund1]

Thanks ClausB, but I think I'm done with this board, for now. It is part of a large Atari lot that I'm fixing for some one else. I am going through it and identifying, fixing, and test what I can.

I pretty sure this will end up on evilbay. If so I will post here when it dose.

Thanks everyone for all you help. Much appreciated!

[ClausB]

OK. In case anyone else has such a board without the loopback, here's a mod to get 48K. As far as I can tell from the photos, the same mod in the link below will work here. Just ignore the part about U15 and R14, since they aren't on this board.

 

http://atariage.com/forums/topic/185500-using-the-atari-400-48k-board-in-the-800/?do=findComment&comment=2669222