I have not completely ceased working on the XF551 board. Contrary to my earlier announcement. Damn thing has a hold on me. My last board has yielded some positive results.
I went back to square one so to speak. I decided to design a board with just the bare essentials necessary. Hopefully to eliminate possible complications due to the mods I wanted to incorporate. It reduced the board space needed and therefor also the cost to manufacture.
On the last test my previous board had failed the drive power on test. I had the data cable on wrong and the cable itself was not made right. I replaced the cable. Then after retracing the board traces I found some mistakes. That’s when I decided to go bare essentials. A few weeks later new board in hand I proceeded to solder in parts. Soldering complete, I inserted my chips. Did a fast power on test and no billowing smoke or loud pop. Good…. Then I attached the new data cable and drive and powered on. I was able to get the drive to spin up briefly when powered on, just like the original.
I began to get encouraged. I plugged in the SIO cable from an functioning 800XL. Powered the drive and then the 800XL and the drive light comes on and stays on. The 800XL beeps and displays ‘Boot Error’. Well… not exactly success, but it tells me that the computer is seeing the drive and communicating with it. At least to some degree. The drive is not spinning, or attempting to seek.
So now I start looking for possible problems with chips and drive. I replaced all the chips except for the ROM and now the drive attempts to load. It gets about a third into the load sequence and then the drive starts chunking every few seconds. Okay, a little further down the road. What if the drive is bad? So I replaced the drive and now it’s singing.
I just about fell down and kissed the ground. So for the record I have a very basic mainboard using a modern power supply and it is loading a DOS 2.5 disk. Here’s the YouTube videos I made.