Should you correct production mistakes?

Tony Duell ard at p850ug1.demon.co.uk
Thu Aug 26 13:45:30 CDT 2010


> 
> On Wed, 25 Aug 2010, Eric Smith wrote:
> > I think the way that I would state it is that just because the system is
> > working correctly (at the moment) doesn't mean that it isn't broken.
> >
> > Part of the reason I don't think we'd fix such a problem in the PDP-1 is
> > that the PDP-1 isn't doing anything criticial.  We can afford to have
> > downtime if a latent problem eventual causes a failure.  If we've
> > properly documented that latent problem, we can check for it when the
> > system does fail, and fix it if necessary at that time.
> 
> Your ability to tolerate downtime is significant, as also is your thorough

That would apply to me too i nthe case of this HP terminal. I am not 
depending on it working. Yes, I want to be able to use it, and I want to 
play about with it, but if it fails I am quite happy to open it up and 
grab the 'scope and logic analyser...

> documentation, so that the repair won't end up in the hands of board
> swappers.
> 
> 
> Y'know, it would be fun to see an entire set of exhibits explicitly about
> failure modes.   Remember the HUH S100 boards for the TRS80, where one of
> the entire early production runs was reversed, but could be used by
> soldering all of the components to the back side of the board?

:-). 

I am pretty sure there ws a DMM sold in the UK which sued as expensiv 
'custom' 40 pin chip. Turns out it was a 7107 or something mirror-flippe. 
You could use a normal one if you soldered it to the otehr side of the 
PCN (and there was enough space to do that.

Sinclar machines are knwon for such bodges -- ICs and/or transistors 
stuck on top of other comonents with kludgewires everywhere. Although 
wether those machines ever worked correctly is debatable :-)

-tony



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