KAYPRO-II U87 MODIFICATION FIELD SERVICE BULLETIN #4 Early Kaypro-IIs have a circuit design problem that can cause the corruption of data on the floppy disk. This design problem was corrected on later versions of the Kaypro-II. Kaypro issued a Field Service Bulletin #4 to detail how to fix the problem with Kaypro-IIs in the field. The information in this note applies ONLY to Kaypro-II models WITHOUT the main circuit board identified as PC81-240A in the front right corner. Check the integrated circuit identified as U87 in the front right corner of the circuit board. It should have two small wires on each side of the chip. If it does not have these wires, they will have to be installed according to the following instructions: 1- Remove IC U87 from its socket. 2- Bend pin 1 of the IC out from the body of the IC. 3- Cut off pin 9 of the IC near the body. 4- Solder a wire from pin 1 to pin 6 of the IC. 5- Solder a wire from pin 12 to pin 15 if the IC. 6- Reinstall the IC, leaving pin 1 out of the socket. 15 12 9 v v v --+---+---+---+---+---+---+---+-- | | > 74LS390 (U87) | | o | --+---+---+---+---+---+---+---+-- ^ ^ 1 6 Pin number I.D. is determined by the notched end of the chip. Remember, when working with IC chips, be careful of static electricity and use a heat-sink when soldering directly to an IC chip to avoid excessive heat transfer to the chip itself. Bill Crocker Detroit Metropolitan Kaypro Users Group