25 Aug
2010
25 Aug
'10
10:57 p.m.
Eric writes:
Tony Duell wrote:
> I could trivially desolder the IC, straighten the pin, and solder it
back
> properly. But should I? What would others do?
Had we found any problem analogous to that in the
PDP-1 restoration,
where the machine operated correctly despite a manufacturing defect, I'm
sure we would have had a debate on whether to fix it. I think my own
opinion in that case would be that we should leave it alone, but tag the
module (paper tag attached with a short loop of string) and document the
issue in the system logbook.
For something that isn't considered a museum artifact, I'd be more
inclined to fix it.
Whatever happened to "if it ain't broke, don't fix it"?
The ability of a robust assembly and QA process to result in working systems,
despite small manufacturing errors, is remarkable. If the board passed QC
and was released into the wild and is still working decades later, that
is a fact worth noting but I see zero reason to correct it. I don't doubt
anyone's soldering skill but there is still a small and nonzero chance
that any attempted "fix" would result in hassles.
When I was in college decades ago, I got to help a civil engineer who
had tried to build a Heathkit maybe 10 years before that but never got it
working. I looked inside, found a few diodes he had reversed, and said that
was the reason. He looked at me incredulously: "You mean a couple of
incorrectly assembled parts will stop
the whole receiver from working?". Yep. "If we designed bridges that way,
there wouldn't be a single bridge standing in the world!"
Tim.
26 Aug
26 Aug
6:32 p.m.
Eric writes:
I've always wondered where that idiotic saying came from. Do you wait
until your car engine seizes before you change the oil? Do you wait for
the timing belt to break voalves to hit pistons before you replace said
belt? Or do you do mainenance?
If you saw a tiny leak fro ma brake sylincer on your car would you carry
ion driving (it's working fine, I csan stop the car), or would you check
that cylidner, replace seals, etc before it failed totally and you ran
into somebody/something?
In the case of classic computers, I always do a visual inspection
inside, chgeck the PSU on dummy load, etc before poweing it up for real.
More than once that's saved me having to replace a lot of parts.
Tony Duell wrote:
> I could trivially desolder the IC, straighten the pin, and solder it
back
> properly. But should I? What would others do?
Had we found any problem analogous to that in the
PDP-1 restoration,
where the machine operated correctly despite a manufacturing defect, I'm
sure we would have had a debate on whether to fix it. I think my own
opinion in that case would be that we should leave it alone, but tag the
module (paper tag attached with a short loop of string) and document the
issue in the system logbook.
For something that isn't considered a museum artifact, I'd be more
inclined to fix it.
Whatever happened to "if it ain't broke, don't fix it"?
The ability of a robust assembly and QA process to result in working systems,
despite small manufacturing errors, is remarkable. If the board passed QC
and was released into the wild and is still working decades later, that
is a fact worth noting but I see zero reason to correct it. I don't doubt
anyone's soldering skill but there is still a small and nonzero chance
that any attempted "fix" would result in hassles.
I can;t think of anythign that could happen when repairing this which
would not itself be curable. If I wreck the IC, well 74LS221s are not
that rare. Alas it wouldn't have an 1820-xxxx numberm but it would work.
If I managed to lift traces off the PCB, I could repair them. It's not a
critical cirucit for layout.
-tony
5238
days inactive
5239
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