26 Jul
2004
26 Jul
'04
9:38 p.m.
Tony Duell wrote:
None of the 1000+ ICs in my PDP 11/45 CPU (including
the MMU and FPU) are
socketed. This has not stopped me repairing it. Actually, I am not sure
what benefits socketed ICs provide for troubleshooting/repair --
desoldering and replacing the faulty IC is not a major job, and you
shouldn't need to remvoe ICs other than the faulty one (in other words
troubleshooting should not consist of replacing ICs until the thing
starts working).
Say, for example, you have multiple open collector outputs connected to
eachother, and for some reason the line is stuck at a certain level. Of
course there are other possible ways, but I think it's quite handy to
remove all connected ICs and find out which one keeps the line at said
level.
Or for example, the PSU prevents the supply voltage from coming up
because the circuit draws too much current. A quick inspection by
removing all ICs and reinserting them one by one is a convinient way to
find out where the problem lies.
If you know better ways than this I would really love to hear about it.
Bert