who came up with the silly rule that a mod that doesn't quite work is preferable to a wire budge that works? if that is really the rules the fix is scrap the boards
You know what the rule is and you know why. The rule is to not allow wire modified boards in the field. Wire modifications are not up to snuff in many regards including reliability and EMI for starters.
That's why I thought the leaded resistor was a good idea. Technically it's not a wire, it's a component with a bit of insulation added to one lead. /;)
What tosh. A wire is as much a component as a leaded resistor. Well applied 'bodge' wire will have little effect on reliability - costs more in production and aesthetics for sure.
You'd have to take a view on whether it is likely to affect EMC, but you wouldn't normally have gone through final EMC without a fully tested product would you?
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Not sure how you can claim a wire is as reliable as any other component. That's a big reason why we have printed circuits and not wired chassis. A leaded resistor may not be any more reliable, but it might serve as a way past the "rules" was my point.
As to EMC, bugs can be found at any time. There is no such thing as a "fully tested product". As we all know, testing can show the presence of errors, but not the absence.
I would expect any seasoned engineer to understand that. Tosh indeed! ![Roll Eyes ::)](https://www.eevblog.com/forum/Smileys/default/rolleyes.gif)
I think you might have gotten the wrong end of the stick - here's some slightly condescending tosh:
A bodge/mod wire should be thought of as a component. It will have resistance, inductance and may introduce undesirable effects (noise pick-up, radiated noise, etc), but a well applied wire is no more or less reliable than a leaded resistor.
There's the problem. You keep comparing a wire to a leaded resistor. No one is saying a leaded resistor applied in the manner of a fixup wire is a reliable component. Please read what I write.
We have printed circuit boards to allow greater complexity and speed up manufacturing. In certain products they still use hand-wired components (valve/tube amps, high-voltage systems, heck even the insides of fairly modern washing machines have relays, sensors that form part of the 'circuit' that are off-board).
PWBs allow much higher reliability in the end product. When I was a kid Zenith advertised their TVs were highly desirable because they were "hand crafted" and "no printed circuits", but the reality was that "hand crafting" was less reliable and printed circuits dominated after just a few years of commercial production.
In mil/space applications printed circuits very quickly became the rule, again because of the reliability.
There is literally no comparison. The lower production cost is just a bonus.
Disagree with the "EMC bugs can be found anytime" argument.
Not what I said. i talked about bugs being discovered after EMC testing was complete.
A well tested product (stable casing/hardware/firmware/software) should test the same regardless of when it was made and where it was tested. So if it's compliant in Lab A on Day B it should be compliant in Lab X on Day Y - there is no spooky action. As usual, the devil is in the detail, and the quality/thoroughness of the testing should ensure this. If the device fails at a later point it should be possible to do a root-cause-analysis and discover what as changed.
EMC results can be changed by any mechanical or electrical changes. I see EMC issues fixed this way, they can also be caused this way. The point is a bug in the system can be found after EMC testing is complete and often is. Adding a wire to fix a bug is much more likely to impact EMI than is a change to the PWB. Traces on the PWB are in close proximity to the power/ground planes so as to minimize radiation and pickup. A flying wire is much less so.
I think we have beaten this issue to death.
![Flogging A Dead Horse :horse:](https://www.eevblog.com/forum/Smileys/default/DeadHorse.gif)