SNYDERS@process.com (John Snyders) (03/19/91)
I just purchased a used spectre GCR. When I started using it in mac mode it would crash. I looked in the documentation and it says that some Mega2s had some marginal chips in them and the solution was to replace them. I checked my machine and sure enough I have the bad chips (SGS 74LS373). I am thinking of doing the work myself and would like to hear from anyone who has had this problem and can offer any advice such as. - Replacement chips used. I would hate to put in new chips that have the same problem. - Tips on soldering. My main concern is heat damage to other chips and the new chips. I have done soldering before but not on a pc board. - How difficult is the job. Is there any thing else I should know. Thanks, John Snyders email: snyders@process.com
s37837k@saha.hut.fi (Jari Lehto) (03/21/91)
In article <28122@dime.cs.umass.edu> SNYDERS@process.com (John Snyders) writes: >I just purchased a used spectre GCR. When I started using it in mac mode it >would crash. I looked in the documentation and it says that some Mega2s had >some marginal chips in them and the solution was to replace them. > >I checked my machine and sure enough I have the bad chips (SGS 74LS373). > >I am thinking of doing the work myself and would like to hear from anyone >who has had this problem and can offer any advice such as. > >- Replacement chips used. I would hate to put in new chips that have the same >problem. Non-SGS 74LS... OR: For improved handling 74HCT373 or even better 74ACT373. They are 100% compatible, but much more faster and reliable. They are essential if you are planning to install an accelerator later... I changed my 1040 to Mega4 and first thing was: 74LS's out and 74ACT back... >- Tips on soldering. My main concern is heat damage to other chips and the new >chips. I have done soldering before but not on a pc board. Small enough tip and keep it well cleaned! Not too hot. Loose the old chips one pin at a time, warm the pin and pull it up with a small screwdriver. If you have IC desoldering tip, use that. Vacuum tin-removers are not reliable for taking ICs off from a pc board... The holes are so small. >- How difficult is the job. Is there any thing else I should know. Not very, but takes a little time... Don't burn your fingers! >Thanks, > >John Snyders email: snyders@process.com Jartsu *** Jari Lehto, jartsu@otax.hut.fi, s37837k@saha.hut.fi ***
wilko@idca.tds.PHILIPS.nl (W.C. Bulte) (03/25/91)
It is not too difficult to replace these chips. I have done this quite a few
times.
What to do: get a good soldering iron (approx 25 watts max)
cut the pins of the LS373 chips
now use the soldering iron and a pair of tweezers (sp?)
to pull the cut pins one by one from the pc board
now use a solder sucker (sp?) to suck the old solder from the
holes.
put in GOOD ic sockets and solder them to the PCB
place the new chips
Off course, as with all good PCB soldering, do it fast. Allow time for the
board to cool in between these operations.
The chips: I use 74F373 chips in my Mega 1, but HCT373 should work allright.
Anything but SGS Thomson should work (so I am told)
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