patten@uhccux.uhcc.hawaii.edu (Brian Patten) (03/28/90)
I'll quickly summarize my problem: I have a Mac Plus whose logic board decided to fail. The local Apple dealer "tested" it and said the board was bad. I asked them exactly what was wrong and they said they couldn't tell me. A new board, with labor, is $450. No way! When I got the machine home, I decided to remove my 1 meg SIMMS and put them in safer storage until I decided what to do. While looking over the logic board, I noticed that one of the chips near the CPU was discolored and had a bubble on the top, near the middle of the chip. The chip has a dark brown, burnwed look to it, and I could barely read the numbers. Okay, now for the questions: 1) The chip calls itself MMI 341-0519-A 747418. It has printed on the board beside it the name "CAS". It is copyrighted to Apple 85,86. Can I get one of these chips? 2) Is this burned chip the cause, or the symptom? Did something else fail and throw lots of current through this poor chip, or is this truely the reason for the failure? 3) If I try to replace this chip, what kinds of things should I take precautions against to protect the rest of the board? I have never attempted something like this. Advice on this problem is very much appreciated. I might also add that on trying to power up the machine, all I get is a screen with alternating black and white vertical bars. The machine does nothing else. Brian M. Patten Institute for Astronomy University of Hawaii patten@hubble.ifa.hawaii.edu
patten@uhccux.uhcc.hawaii.edu (Brian Patten) (03/29/90)
Thank you one and all who took the time to send me advice on what to do with my bad Mac Plus logic board. I am having problems with the local e-mail, so I am unable at the moment to send personel replies to those who sent me advice. In case you are wondering, I have decided to order a replacement for the burned HAL chip and will replace it on the board myself. We have a lovely electronics shop downstairs from where I work, and several people in the shop have offered to help me with the work. The adventure continues... Brian M. Patten University of Hawaii Institute for Astronomy patten@hubble.ifa.hawaii.edu