Thanks! REXT Diagnostic ROM and POSTcard

Andrew Lynch wrote: The DRAM I could probably figure out myself, but how did you determine the 74LS245 was at fault? (I, too, have a 5150 that won't boot) -- Jim Leonard (trixter at oldskool.org <http://www.classiccmp.org/mailman/listinfo/cctalk> ) http://www.oldskool.org/ Help our electronic games project: http://www.mobygames.com/ Or check out some trippy MindCandy at http://www.mindcandydvd.com/ A child borne of the home computer wars: http://trixter.wordpress.com/ -----REPLY----- Hi, The old fashioned way; I used an oscilloscope to compare the inputs and outputs of the bus transceiver. One of the buffers was dead and all of the outputs on one side looked "funny" so I desoldered it and replaced it with a new one. Of course, the IBM PC/XT motherboards have few sockets so desoldering and replacing the chip was awful. I tried to nicely desolder it but ended up destroying the chip and cutting it out. One thing I really like about VG, NorthStar, Kaypro, and Heath is almost their entire motherboards are socketed. Yes, I know direct soldered chips are technically more reliable but they are a PITA to replace when they do fail. Thanks and have a nice day! Andrew Lynch