The calculations...

[Tony Allgood]

Ingo writes:... But look at commercial electronic devices, you'll often
find wires on the PCBs. And these are from series production, while
yours is the first prototype.

One project I worked on went to 7 iterations of a PCB before it went
into final production. Not my bit thank heavens, that only went to
four!! Part of the problem as well as engineering mistakes, which do
happen for sure, is marketing sticking their oar in too late in the
design stage. "But we wanted five flashing lights not just two..."

The other engineering thing is unforseen problems... "Where the hell is
that 10MHz oscillation coming from" Mmm, this happened to me very
recently (Thanks Jorgen!!). But mistakes are funny things, we feel like
kicking ourselves when we find them. How could have I missed that one?
But we do, and time and lack of experience are often to blame. That's
why it is always nice to have two people on a design. Get the other guy
(or girl?) to check the design before you put it to PCB. Most big
companies insist on this anyhow, but once again, time constraints often
cause this essential review to be missed. Of course, if it is all you
own work, you have to be especially careful.

It happens with music too. I have just had to redo some of my older
tracks to get rid of the uncleared samples from them. But for every new
mixdown I did, I would always find something I wasn't happy with... if
not then, but the day after. However, just like engineering, there comes
a time when you have to freeze the design/mix and put it to PCB/CD. And
just cross your fingers...

Regards,

Tony Allgood  Penrith, Cumbria, UK

Modular synth circuits, TB303 clone and Filter Rack

http://www.techrepairs.freeserve.co.uk/projects.htm