exxos's Atari, Amiga & retro forum

Howdy Fellow ST family...

I purchased the [4MB MMU TYPE RAM UPGRADE]
Long story short, ended up paying extra because I bought each needed piece separately.. (A different story)

To my surprise, I'm having problems. I had my Atari ST modded out as a teenager, however today re-living that is different on my
Atari 1040 STf (1MB) system.
From reading the instructions here;
https://exxosforum.co.uk/atari/last/4MBMMU/index.htm
I can't find a good video tutorial on this.
It seems opening resistors and adding voltage to them is not necessary w/ this specific MOD. Is that correct?

(Update) Noticed a short mention of removing old ram. Is that necessary? Can't connections be cut?

I pulled the MMU PCB mod off/on a few times now and would rather ask before pins get bent.
Everything looks alright to me, but obviously not.
Do I need to press the Board down all the way in?
Im getting 20 bombs at boot.

(Will upload pics via phone)
:?:

You need to remove all the old ram. If it doesn't work after then you likely have a bad connection somewhere.

Aside from what @exxos mentioned, I see you seem to have a side cartridge installed, so I'd recommend removing all mods so you have a standard mainboard and you make sure that works first. Then add the memory expansion and get that working before you add the Sidecart again. Trying to troubleshoot too much at once usually means you are fighting against things, so go back to the basics first.

BTW lifting resistors and applying 5v is the minimum as it disables the old RAM, ultimately removal of the old RAM is better, but only when the expansion works.

Also be 100% sure you have the MMU adapter correctly lined up with pin 1 of the MMU.

Good spot @rubber_jonnie . Indeed ALWAYS going back to a stock machine when troubleshooting.

It reminds me, I started a FAQ about this stuff. I just uploaded the updated page.

https://exxosforum.co.uk/atari/last/4MBMMU/index.htm

rubber_jonnie wrote: 20 Nov 2024 09:24 I'd recommend removing all mods so you have a standard mainboard and you make sure that works first. Then add the memory expansion and get that working before you add the Sidecart again. Trying to troubleshoot too much at once usually means you are fighting against things, so go back to the basics first.

BTW lifting resistors and applying 5v is the minimum as it disables the old RAM, ultimately removal of the old RAM is better, but only when the expansion works.

Thanks for the reply. I was afraid of that.. I have the full 1mb version..
I completely agree with bringing it down to "vanilla" when adding new..

Could someone point me to the resister lift / bringing them high method?

WilsonB wrote: 20 Nov 2024 19:51

rubber_jonnie wrote: 20 Nov 2024 09:24 I'd recommend removing all mods so you have a standard mainboard and you make sure that works first. Then add the memory expansion and get that working before you add the Sidecart again. Trying to troubleshoot too much at once usually means you are fighting against things, so go back to the basics first.

BTW lifting resistors and applying 5v is the minimum as it disables the old RAM, ultimately removal of the old RAM is better, but only when the expansion works.

Thanks for the reply. I was afraid of that.. I have the full 1mb version..
I completely agree with bringing it down to "vanilla" when adding new..

Could someone point me to the resister lift / bringing them high method?

If you look at the FAQ's at the bottom of the info page from the shop it goes into the resistors you need to lift and feed 5v: FAQ's

exxos wrote: 20 Nov 2024 10:07 I started a FAQ about this stuff. I just uploaded the updated page.

https://exxosforum.co.uk/atari/last/4MBMMU/index.htm

The FAQ helps

What Flux is that you use/recommend in your videos?

WilsonB wrote: 20 Nov 2024 23:45

exxos wrote: 20 Nov 2024 10:07 I started a FAQ about this stuff. I just uploaded the updated page.

https://exxosforum.co.uk/atari/last/4MBMMU/index.htm

The FAQ helps

What Flux is that you use/recommend in your videos?

Personally when I use flux I use Kingbo RMA-218. It works very well and is easy to clean up. I mostly use it for desoldering as I use flux core solder when I'm soldering components in place. It's good for SMD work particularly.

It's a gel type flux.

WilsonB wrote: 20 Nov 2024 23:45 What Flux is that you use/recommend in your videos?

https://www.exxosforum.co.uk/atari/store2/#0262

Ok, I have had it working 5 out of 8 re-seats.

The big question most customers will have when looking very closely, does the pins of the MMU daughter board go behind (farthest out) or inside between Chip and pins ?
Maybe I missed a close-up somewhere, but did not see it specifically.