<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta content="text/html;charset=ISO-8859-1" http-equiv="Content-Type"> </head> <body bgcolor="#ffffff" text="#000000"> To add to this story a bit, I had just started working (engineer in the Ham Radio department) at Heathkit in the summer of 1977 and purchased one of the very first H-89s off the production line. After waiting for what seemed like a jillion years (actually about 3 or 4 weeks), they started shipping them and I picked mine up at the store at the main plant in St. Joseph. But it didn't have a disk drive (i.e. it was effectively an H-88 with only a tape interface) because there was some sort of a problem involving the disk drives and they were holding them until the problem was solved. After several weeks (?? not sure how long it took but I did learn to really, really appreciate disk drives after coping with a cassette tape drive), the mod kit and the drives were finally released. It seemed that, as Lee commented, the disk drives (only 40-track, SS SD) were being corrupted by electrical noise from teh HV, CRT, et al. The solution was a mu-metal shield. Didn't know about the 80-track problem but I ran DS DD drives in mine with nothing but that mu-metal shield. Memories! Bob Groh Heathkit Engineer 1977 to 1981 Lee Hart wrote: <blockquote cite="mid44297CBE.B3CAFBFB@earthlink.net" type="cite"> <pre wrap=""> Heath was actually rather brave (or ignorant) to put a computer in the same box with a CRT, without any of the usual shielding around the CRT. The CRT, flyback transformer, and associated high voltage wiring can cause corona, arcing, and electric fields that wreck havoc on sensitive circuitry. The disk drives were the most sensitive to CRT noise. 80-track double-sided drives were the worst offenders. Heath finally came out with the H88-9 kit to totally enclose the disk drive in a steel box, which was carefully bypassed and grounded to keep CRT noise out of it. </pre> </blockquote> </body> </html>