Atari 1040 ST Ram expansion for C070523-001 (anyone?)

[AA_ron]

Has anyone performed this project?

 

I have 2 of the 2M boards, and chips (from a SIMM) and intend to up my 1040STF to 4MB.

I'd prefer some official instructions & hear someone's experience before attempting it.

 

For example, the shared project says to replace 2 capacitors, but no other detail about that.

 

https://www.pcbway.com/project/shareproject/Atari_ST_Ram_expansion_for_C070523_001_66a501cd.html

[TZJB]

11 hours ago, AA_ron said:

Has anyone performed this project?

 

I have 2 of the 2M boards, and chips (from a SIMM) and intend to up my 1040STF to 4MB.

I'd prefer some official instructions & hear someone's experience before attempting it.

 

For example, the shared project says to replace 2 capacitors, but no other detail about that.

 

https://www.pcbway.com/project/shareproject/Atari_ST_Ram_expansion_for_C070523_001_66a501cd.html

 

I have not tried this method of DRAM expansion, but the 514400 1MB SOJ lead DRAM is often used to replace the DRAM in Atari STs with existing SOJ lead DRAM.

 

Looking at this project and although they are not included in the BOM, I think the author Meinrad Duepre is talking about the two large electrolytic capacitors for the 5V supply. Ignore that unless they seem damaged.

 

Once installed it should provide a very reliable 4MB memory expansion.

 

If you can recover the 41256 DRAM without damage they may be used elsewhere.

 

Best of luck!

[AA_ron]

10 hours ago, TZJB said:

 

I have not tried this method of DRAM expansion, but the 514400 1MB SOJ lead DRAM is often used to replace the DRAM in Atari STs with existing SOJ lead DRAM.

 

Looking at this project and although they are not included in the BOM, I think the author Meinrad Duepre is talking about the two large electrolytic capacitors for the 5V supply. Ignore that unless they seem damaged.

 

Once installed it should provide a very reliable 4MB memory expansion.

 

If you can recover the 41256 DRAM without damage they may be used elsewhere.

 

Best of luck!

Now that I look more closely, the board does have labels for "MAD9 from MMU", a hole for "from or to another Rambank", and R1, C1-C4 which are in the BOM.

I'll add the standoff leads and follow the board & BOM.

 

Thanks for the opinion that the side suggestion was just a standard re-cap.

Not sure exactly when I can jump into this, but I'll try to come back and provide results.

 

[TZJB]

7 hours ago, AA_ron said:

Now that I look more closely, the board does have labels for "MAD9 from MMU", a hole for "from or to another Rambank", and R1, C1-C4 which are in the BOM.

I'll add the standoff leads and follow the board & BOM.

 

Thanks for the opinion that the side suggestion was just a standard re-cap.

Not sure exactly when I can jump into this, but I'll try to come back and provide results.

 

 

You are correct. The MAD9 needs to extend from the MMU pin 64 to both 2MB banks of memory via R1 in order to provide Address9 to all of the DRAM memory.

 

Connectivity is normally to the MMU pin 64 underneath the motherboard for reliability.

 

Shown here with the 33R resistor that will already be on your memory expansion PCB. Note that MMU Pin 1 is the square solder pad at the bottom middle of the chip in this case:

 

 

As you already have a 1040STF with two 512kB banks of memory, the resistors from the MMU for the second memory bank will already be in place, minus the MAD9 connection of course.

 

You might consider an alternative 4MB upgrade from @tf_hh. Jurgens' devices are well designed and pre-tested. They also require soldering but probably not as much as you are already considering.

 

https://www.van-radecke.de/STUFF/tfhh_HW_info.pdf

 

Download manual / instructions here: http://www.van-radecke.de/ST/ST4MB.pdf

 

Best of luck whatever you decide.