First post, by majestyk
From my heep of unrepaired mainboards I recently pulled a FIC 486 SC-P that´s based on the "Symphony Haydn" chipset.
I ran some tests and to my surprise everything seemed to be fine. But after a while the thing started acting absolutely crazy. It either wouldn´t POST at all or give some random AMI BIOS beepcode like defective RAM, missing video adaptor, defective video RAM, CMOS read error and many more- some of those might even not exist. The next day all was fine again.
During some further troubleshooting with coolant spray I found the culprit: As soon as the chip that handles all the peripheral stuff like RAM and ISA-bus, a "SL82C362", was cooled before startup, the system worked in about 95% of the cases.
First I checked each and every pin of this chip but all solderings were still in perfect shape. So replacing the chip it is!
This is the original situation:
My usual "strategy" is as follows:
1. cut all the pins where they come out of the chip with a Dremel.
2. carefully remove the remaining ends of the pins with a regular soldering station
3. clean all the flux and dirt carefully
Here´s the mainboard after I did this:
and here´s the old chip:
4. carefully position the new chip and solder all pins the oldschool way.
Problem in this case is I cannot find a new replacement for this chip today so I will have to use a chip from a donor-board. I´m quite sure I have some damaged Haydn board in the basement.
But how do I safely and carefully remove the chip without damaging it by overheating or mechanically?? I have never done that before because I was always able to find new chips for replacement or I had to deal with far smaller QFPs thad could be desoldered easily.
Any tips welcome here!