After double-checking all connections I turned on the power to the ST. There was no smoke or loud pops so that was good
but the screen just stayed white. It never made it to the desktop and there was no PAK logo. I felt the chips on the PAK and nothing was hot, but I turned off the computer after 10 or 15 seconds. I did try a couple more times, but always a white screen.
So the first thing I did was remove the PAK and put the old 68000 cpu back in the motherboard to make sure the ST still worked. Sure enough it booted fine no problem. The issue was with the PAK it seemed. My first thought was to put the 68000 cpu in the PAK and set the board to run in alternate operating mode. But GAL U3 under the cpu socket was itself socketed which made it too high and there was not enough clearance to put the 68000 in.
This just required some 32pin SILs added to raise the 68000 up, but for the future, I would like to directly solder GAL U3 and the F86 to reduce the overall profile of the PAK. Also, jumper J5 was removed for alternate operating mode.
Unfortunately, the white screen remained. Looking at the manual, I saw that in addition to J5 being removed, jumper J6 also needs to be open.
Removing J6 and retesting resulted in disappointment as the screen stayed white. I removed and verified the PAK-TOS roms (and printed new labels with their board locations which I thought was better) and they were correct. So at this point I wondered if the previous owner had damaged the board since he had shipped me the board with the GALs reversed. Since I had intended to try 32MHz speed after the PAK had been set up I had the 68030RC33 and the oscillator at hand. I removed the old cpu and oscillator and fitted the replacements.
Placing the PAK back in the ST and powering on I was greeted with a nice PAK logo. Progress! Unfortunately, that was it...it never would move past the logo to the memory test or desktop.
I then tested it in alternate operating mode with the 68000 and it still was stuck at the logo. Making progress, but still not there. I removed the 68882 fpu and FPU-Enable jumper J3 and tried again. Still only the logo.
Since I was using Petari's improved TOS 1.04 on the mainboard, I considered maybe the PAK's boot patch was overwriting something and causing the hang. So I burned a straight vanilla TOS 1.04 and tried again. Still stuck.
Thinking about the problem, it seemed the switchover GAL was important for both the 68000 and 68030 cpu so I decided to change it. I was surprised to see a capacitor in the socket under the GAL. Not sure if that is in the manual, but I will need to read it again and see if it is mentioned.
After connecting the PAK back up and switching on the power I was happy to see the memory test and then the desktop!
This was a very encouraging development! However, all is not quite well as I will explain in the next post.
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