exxos's Atari, Amiga & retro forum

Hi all

So the Atari 520stfm arrived from eBay. I began work on recapping the power supply.

Second job; rom upgrade. I have a C070789 revision B. I find atari in their cost saving measures don't include jumpers to select if 256kb or 1 meg tos roms are installed. I later learn two chip (1mb) version of tos 1.04 is rarer than hens teeth.

Out comes the soldering iron. 1mb bridges on A17, A16, and above the one above the MMU are desoldered. Then disaster; I lifted one rightmost 1mb pad above the MMU.

Iron I had at 350 degrees. The assembly line sure like their solder blobs and flux mess which was never cleaned up.

Lifting that 1mb single pad is more of an annoyance than an inconvenience as it won't effect anything once I converted the machine to use 256kb roms via the t48 eprom burner.

Fixing that lifted pad my OCD cries out to fix still. I guess things happen when the universe wants you to learn a new skill, so post those suggestions for pcb pad repair :)

I keep you posted how the other upgrades go. Exxos kindly dispatched my 4 meg upgrade, promptly and am now waiting for a GoEx gotek drive to arrive.

Work and 12 hour shifts mean I not get much time to work on hobby projects, but am glad I find this place, and the likes of Exxos and the community I have already learnt a great deal from.

Nice diary. Keep us posted. Good luck

Pictures please :)

Work on progress...

Still waiting on the set of 256kb eproms to arrive in the post from an eBay seller. Then I shall post some more details on the progress.

Other news; the GoEx arrived today (a newer version of the GoTek that uses a thumb wheel and SD card) so no bulky rotary encoder or usb stick will be sticking out the side.

Help !

l now have the 6 eprom sockets fitted with 6x TOS 1.4 programmed EPROMs (each 256kb).. I now need some help !

Upon powering up with the floppy and keyboard attached, I'm now getting 4 bombs on screen. Tried taking out the EPROMs and reseating them, but still the same problem.

Checked continuity on the dedolder 1mb pad bridges on the board. They are open circuit as they should be after desoldering them. The 256k pads I bridged for using 256kb Eproms are beeping on continuity test with the multimeter so things should be working but they are not (still getting 4x bombs on powerup).

Could it be the RAM? I only got 512kb of on board RAM... Does TOS 1.04 need more RAM to work?

Awaiting for your suggestions !

Did you change all 3 solder blobs on the motherboard?

Yes, all three solder bridges changed. That includes two near the rom sockets, and the other near the MMU. 3x 1mb solder bridges desoldered and 3x 256kb bridged with blob of solder.

On powerup, power LED illuminates, yellow keyboard LED comes on. Red disk drive light illuminates and disk drives checks if their a disk in the drive, and then white screen and four bombs onscreen.

Any help on this please?

I'm not particularly knowledgeable about such things but some photos of the jumpers/soldering might jog a few minds :D