i meant an updated schematic


i have several 1 mb stick lying around

and now i KNOW it actually works im gonna put them in too

I have redrawn the mapper part of the image.

Thanks Erik!

The circuit diagram and the additional instructirons are now added to the diy page.

Erik,

I just made a Visio drawing based on your drawing and send it over to Hans. I could'nt find your mailadress so thats why i'm also posting it here.
Hope that you dont mind that I copied your drawing, otherwise please let me (and Hans) know.

Hi Luppie,

looks nice, no problem. I like yours better then mine.
Also I added another simm to this computer and now have 2mb in it

Erik

Unfortunatly my upgrade was not succesfull, so I removed the SIMM and placed back the original memory, but still no luck.
This evening I'm gonna remove all the added IC's and bringing back my 8255 in it's original state.

With turning the PCB many times arround I also pressed the service switch a couple of times and I dont know in what state it should be (pressed or un pressed)

cool will it olso work in a nms8220 or just the 8250,55,80?

the service button should be up (not pressed)
Do you have a mem expansion cartridge? That way you can also test if the machine still works

Yep I have a 512Kb mem mapper from MSX Club Gouda.

@app_en_koe44 :

NMS8220 upgrade to 128K

Place on top of the existing two 41464 on each another 41464. Dont connect pin 16.
Connect a wire to the pin 16 of both IC's and connector pin 35 of the M60003. Also move the bridgewire J2 to J43 to get a 128K report after startup.


Source : http://msx.retro8bits.com/memory-and-mappers.html

Does your machine work with the external mapper inserted? Did it work after you removed the ram ics and before you added the extra ttl logics?
This way you can backtrack your problem. Do you know if your ram ics are still working?

Hi Luppie I just noticed a fault in your drawing.
D3 of IC149 should not be connected to D4 of IC149B.
D3 comes from pin 11 IC 161 and D4 comes from pin 11 IC 176.
Maybe that is your problem

I'm gonna try tonight your supposed sollution.
I also bought 12 new ram modules and if the machine is working again, I gonna use this upgrade to 512Kb:

http://msx.retro8bits.com/msxdocs/nms512kmemory.pdf

This one is easier to implement. If the machine stays defective I have to buy a new one so then I got a lot of spare parts

Dont be fooled by the document. I also have a machine in which I put 16 41464 ics and that was not as easy as you think.
Getting the ram ics nicely on each other so that no pins of each stack connect to each other is not easy as it looks.
The SIMM implementataion was easier for me and also a lot cheaper as those ram ics are not that cheap.

I also sent you an email. If you want to discuss further offline

Hi Erikie,

can you post the necessary arrangements to connect 2x1Mb SIMM ?
I have been searching, but SIMMs > 1Mb are quite hard to get

Hi Mohai,

You can download that document from the website of Hans O
It is not so hard if you already did the 1mb job to modify it to 2 mb.
here you can find the document: http://msx.retro8bits.com/memory-and-mappers.html

Erik