PCB patches in commercial products, how common are they?

Thread Starter

cmartinez

Joined Jan 17, 2007
6,462
I had to open a small device I bought a few weeks ago to make an adjustment in its internal jumpers. The device in question is a step motor driver that sells for $158.00 usd.

To my surprise, I found that it had a small patch in its circuitry in the form of a hand crafted jumper cable. It looks kind of ugly, but it does the job.

262f4d82-663f-4b6d-ba03-c090dcd8ec53.jpg

As far as I'm concerned, I couldn't care less how it looks, as long as it functions properly and doesn't affect functionality nor durability. But I would've guessed that a company as respectable as this manufacturer would've been more careful in its design. I guess we're all human after all, and every once in a while someone screws up, no matter how prestigious or technologically advanced.

How common is this kind of mistake in the industry?
 

Thread Starter

cmartinez

Joined Jan 17, 2007
6,462
And here's another interesting bit I've just noticed. One of the smt resistors in the above pic is mounted on its side!

upload_2019-3-17_21-28-19.png

 
Real estate is expensive. Side mounted resistors generally have a lower inductance,
e.g. A single value resistor won't work in some designs. Three resistors in series mounted on the edge has less parasitics.
 

AlbertHall

Joined Jun 4, 2014
8,358
I worked for a company that made oscilloscopes. One model ended up with 31 modifications which was the limit for the mod label so they called those 31 mod 1 and started again. It got up to mod 5 on the new scheme. Not many of those were extra wires and one of them reversed the action of a previous mod. I wonder if the design team still got their bonus.
 

SLK001

Joined Nov 29, 2011
1,504
And here's another interesting bit I've just noticed. One of the smt resistors in the above pic is mounted on its side!
I wonder if that was just a 0ne-off. Most pick-and-place machines can't place a part on its side like that. It probably was pulled up like that during the reflow process. Placing it like that makes it very vulnerable to damage (usually taking the PCB with it).
 

dl324

Joined Mar 30, 2015
8,891
When I worked building computers back in the 70's, HP allowed a certain number of wire jumpers (to overcome defects in multilayer boards) before boards had to be scrapped. There was a specific way that the wires needed to be soldered and routed and a maximum number of jumpers allowed. Sometimes the jumpers were needed when traces were lifted; other times, it was an inner layer open.

Quality should be better now.
 
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ElectricSpidey

Joined Dec 2, 2017
688
Over the years I have purchased many a surplus board to harvest the parts, and many of them had patches on them.
 

dl324

Joined Mar 30, 2015
8,891
I had some boards for a homebrew EPROM programmer. One revision had a short and the person who made them repaired each board before selling them. In my case, I got some boards in a parts swap and I needed to do the modification.

Since it was his mistake, it made sense to repair them.
 

Ian Rogers

Joined Dec 12, 2012
662
A lot of my commercial products have patches.... I'm rubbish at getting it right first time... I'm getting good at masking them though.. Try and make it look like the patch goes there...
 
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