KFs STFM Ultimate STFM Upgrade Odyssey

[krisfeigl]

Another update.

Carefully removed the 2 old 28 pin TOS sockets and soldered in EXXOS Dual Bank ROM board and I think its in 1.04 TOS mode and the board is in GLUE mode so it should POST okay but NO CHANGE with either original CPU or the 2.3 booster in the tested CPU socket on my SM124.

I then stupidly recalled that I had never tested this setup with anything but the Monochrome screen in Hires mode. I plugged in my 15khz syncing Samsung flat panel and lo and behold I was always getting A DARK RED(BURGUNDY) SCREEN in color low med res screen mode. From what I understand this indicates BAD RAM which might imply that my 4mb ram board is actually the problem and that I didnt test it for long enough b4 I had continued with the mods.

I have the TOS jumper in the lower position which I think is TOS1.04 rather than the 2.06 bank which I know cannot work EXXOS?

When I put in the 2.3 booster I have just left it as is with no wiring as I think Exxos said it defaults to 8mhz that way anyway I THINK?

How am I best to proceed with this RED SCREEN. Should I remove the 4MB RAM Board and put in 16 sockets and put in 512kb of ram to see if that gets the unit to POST again? I have already tried resoldering the points on the underside of the board and I definitely had the 1mb/4mb coming up and ran 3 or 4 mem tests successfully b4 I continued with this project. Maybe the stress of pulling and pushing on the TOS and or CPU sockets are what started all of my problems.

Any suggestions appreciated but this RED screen at least gives us something to go on

[exxos]

Have you metered out the ROM lines back to the CPU as previously suggested ?

[krisfeigl]

How would I go about metering the rom lines back to the CPU?

The service manual available for the ST suggests that a failure of RAM is what will produce that dark red screen at power on.

I need to get a hold of a diagnostic cartridge or remove your RAM board and put in a bank of dram.

I knew I should have put in dram sockets and placed your board carefully into the sockets to facilitate troubleshooting.

Ahh well the red screen is understandable considering the initial flakiness of the 4mb RAM board installation. I should NOT have proceeded with just the 3 or 4 RAM test passes.

Anyway if you can describe metering the rom lines I will try and do that to eliminate further possibilities

[exxos]

You need to continuity check all the address and data lines from the ROM to cpu. You also need to check all the signals to the ram check out from the MMU & DRAM etc.

It will make diagnosing hard work as you swapped 3 things at once and there is no easy way to trouble shoot a dead board. Diagrom may well be the only option to trouble shoot. The Atari diagnostics software does at least need a attempt to boot from ROM to boot the diagnostic cartridge. Diagrom is stand alone.