INSTALLING A 1571 DRIVE BOARD IN C128D (PLASTIC CASE)    4-20-2022

     The C128D in the plastic case uses a standard C128 motherboard with some modifications to allow the use of a built-in 1571 disk drive. That drive board is different than a stand-alone 1571 drive. Although the two are electrically similar, trying to diagnose one with an alternate schematic is frustrating. I did eventually find a print for it and made some corrections but still had no luck in diagnosing my 128D drive. 
     I tried many times to repair the original drive board in my European C128D computer but the board had been "worked on" before and I never could diagnose and fix what was done to it. I did have a few spare boards from stand-alone 1571 drives since many are unrepairable with bad heads. The replacement board is a bit larger than the original so fitting it is a bit tricky. I'll describe how I did it here with a few photos included.
     The 1571 board will just fit inside the 128D and the drive connections will plug in just fine. I had to make an adapter cable to supply the new board with power. Another adapter was made to connect the serial port of the computer to the drive board after removing its serial connectors. The head wires were a bit short so I had to cut the tie that held them to a metal post and this still allowed enough flexibility for the head to move. The drive LED must be plugged onto the connector offset, as shown in the photo. Mine didn't work at first but resoldering the intermittent connections on the tiny LED board corrected that problem. 
     There was no easy way to mount the new board. Because it has a metal shield on the bottom, I thought it safe enough to just set it in place where the old board was installed since there is nothing underneath for it to short out. I did have to break off the metal stub that held the old board to allow the new one to sit lower. The wiring to the new board will not allow it to move very far inside the case but I put a foam pad on top of the board which is compressed when the top cover is reinstalled. That pad further keeps it from migrating around when the computer is moved. There wasn't enough room to put the metal cover over the drive mechanics unless I did some hacking but I thought it unnecessary to put it back... same with the shield over the drive board. 

Ray