XT Memory Expansion Card?

[Dallas_Green]

Hello community
I found this old card in my Compaq Portable while I was disassembling it. It seems to be a RAM expansion card from a 3rd vendor since it appears slightly different to the other parts.

I was wondering whether someone has a glue how this card is supposed to work? There isn't any vendor or model name marked, so its gonna be hard to find a documentation about. Also the jumper setting would be interesting.

I know, the card is in quite bad condition. I already removed the accumulator but the corrosion which it acid let behind already spreaded a lot. So I tried to give it at least a brush with Isopropyl alcohol. Guess it needs a way more attention later but first I wanted to ask you whether there is hope to get it back to work without any information about it?

 

[Dallas_Green]

Also I wanted to check what the Portable says about the presence of the card.
But the post stops with two messages. Then it stops.

4020 201

Then later:

PARITY CHECK 2

I just found this thread and comment to this parity check and it seams to be a not working Expansion memory card then. But this doesn't surprise me looking at the shape of some pins of certain ICs. Also some of the jumpers just rusted away. This is why I'm also looking for something like a documentation about.

 

[NeXT]

That looks like an EMS + RTC + Serial + Parallel multi card. (AKA a clone of the AST six-pack plus) It has what looks to be 384kb of ram installed on it as well, so I assume without that card installed you have 256kb of memory in the computer?

 

[Dallas_Green]

You are right, it looks quite similar to this. I found some details about here and also on minuszerodegrees there is a manual about the original card. Nevertheless it's not exactly similar. The jumpers are completely different, there is no joystick port and as far as I see it could handle more ram then the original one.

It's hard to find the manufacturer of the card if they can't put even a single little model number on it ^^

 

[jafir]

Also I wanted to check what the Portable says about the presence of the card.
But the post stops with two messages. Then it stops.

4020 201

Then later:

PARITY CHECK 2

I just found this thread and comment to this parity check and it seams to be a not working Expansion memory card then. But this doesn't surprise me looking at the shape of some pins of certain ICs. Also some of the jumpers just rusted away. This is why I'm also looking for something like a documentation about.

There is a doc here that explains the error: https://minuszerodegrees.net/manual..._Plus_286 - Maintenance and Service Guide.pdf

Here is a snip from the doc:


------------------------------------------------------------------------------
* Location of Failed Chip if using Alternate Bank 2 and 3.
==============================================================================
Table 5.4-5. COMPAQ Portable and COMPAQ PLUS Extended Memory Codes
==============================================================================
xx Code Beginning Address
------------------------------------------------------------------------------
40yy 201 256 Kbytes
48yy 201 288 Kbytes
50yy 201 320 Kbytes
58yy 201 352 Kbytes
60yy 201 384 Kbytes
68yy 201 416 Kbytes
70yy 201 448 Kbytes
78yy 201 480 Kbytes
80yy 201 512 Kbytes
------------------------------------------------------------------------------
yy Code Failed Bit
------------------------------------------------------------------------------
xx00 Parity Bit
xx01 Data Bit 0
xx02 Data Bit 1
xx04 Data Bit 2
xx08 Data Bit 3
xx10 Data Bit 4
xx20 Data Bit 5
xx40 Data Bit 6
xx80 Data Bit 7
==============================================================================

 

[Dallas_Green]

Thanks for this Link. Well, it explains then why it must have something to do with the extension memory card since the PCB has about 256k soldered and socked and from their on it was supposed to check the ram on the card then... what failed in the end.
Guess this is because of the missing jumper setting or some damage caused by the corrosion. :/

 

[modem7]

Guess this is because of the missing jumper setting or some damage caused by the corrosion. :/

More than likely, the bit 5 chip in the first bank on the card. And rather than the chip actually failing, it might just need to be re-seated in its socket. Swapping the bit 4 and 5 chips within the first bank would reveal which one.

 

[Dallas_Green]

Hello all
After some time I had some time left to give it another try. A saw that one of the net resister was physically broken and also the pin header for the jumpers needed to be replaced. The little bin bridges where already destroyed by the corrosion. Also I cleaned the rest of the corrosion with isopropanol.

Unfortunately now the card doesn't work at all anymore. The XT doesn't even POST with the card mounted and the AT just continues beeping without POST.
So it seams that I broke the card somehow. Maybe by soldering or since its an multi-layer board, the isopropanol got between the layers and destroyed something inside there, is this possible?
Is there any chance for this card? Quite hard to get further now.

Thanks and regards
William

 

[onre]

Isopropanol can't really destroy anything.

 

[twolazy]

I give it a good vinegar bath, then test again. If still errors, I foresee a bunch of de-soldering and adding sockets in your future.