Sounds like a good example of a non-technical person participating in the design. We would get crazy stuff like that from sales all of the time...what seems logical to others can really play havoc with electronics design. That is why a lot of distributors have an engineering staff - to keep their sales department from making promises they can't keep.
The other downside is that the assemblly line workers learn nothing! So when a decision has to be made it will be the same one over and over again since that is the way it is always done. No thinking. No initiative.
It would be nice to allow the assembly line workers to grow in their craft. Reading resistors and capacitors is a very good start. That way when a mistake on the drawing is made, someone can catch it before 1000 boards have to be reworked or thrown away.
I agree that replacing the name "R1" to "10K" would remove some ambiguity during assembly, but isn't that what a BOM is for? Plus they have 1 letter of silk screening or printing of whatever sort. Not sure if they are paying by the letter. Plus schematics, if drawn properly, have all the info needed per component, right?
When the PCB shrinks and populates the boards to the point where silk screening will not help at all, what do we do? What will human hands do then? I worked at a place where they have one person "who was good at the little parts." They would handle surface mount components. After seeing their not-fantastic job are rebuilding, I just printed and placed another board.
Oh yeah... R1 may change in the future... all the "10K" printed boards would be an issue.
There are two purposes for silkscreening component numbers on a board - to populate the board with the correct components, and to be able to troubleshoot the board at testing. The second is where the system described here failed miserably.
Let's say you have a board with 3 capacitors labeled "C1" and 10 resistors labled "R1". Your schematic shows two different "C1"s connected to five different "R1"s. If one of your "C1" capacitors has popped, how do you find it on the schematic to troubleshoot it?
Another reason to use "R1, R2..." and not the component values on the PCB silkscreen. As soon as a design revision or a new configuration requires one of the component values to change the silkscreen will need to be changed. All the existing bare PCBs will need to be re-labeled or scrapped.
As component sizes shrink and physical density increases, silkscreening the reference designators becomes impractical. We were spending many hours re-arranging the CAD-generated text so it was not covered by components or superimposed over a solder pad. The result was almost unusable in crowded areas of the PCB. Everyone in the design/ manufactuing/ support chain agreed the pain exceeded the gain so most of the silkscreen was deleted. That said, we have online tools that link BOM, schematic, and assembly drawing. Click on one, and it highlights the item in the other two.
@takochip- Yes, understand the motivation and "requirement" that led to it. My point was that if, for example, a location marked as "10k" needs to be changed to a 15k value, the silkscreen is now wrong. That means modifiying each board or scrapping them. Special work instructions could be generated to pull from the 15k bin and install it at that location which is marked "10k". You can imagine the potential mistakes that will result !
There are pros and cons for doing it any of the ways mentioned, all have drawbacks and advantages, it all depends on who's driving the bus (usually bean counters these days).
Obviously, these boards were labeled with assembly in mind and not repair, it was not mentioned whether or not these units were intended to be throw-aways or not, if they weren't, then this decision was not particularly wise.
As to the trouble shooting aspect, I have a VHS deck which is in need of recalibration, I have the full service manual and schematics, the calibration procedure is given in full, the problem being is that there are no test points on the board labeled and the calibration procedure does not indicate where to put your probes to monitor the signals for adjustment. This makes it very difficult to do the calibration. I've done this calibration procedure a great many times over the years with quite a few different types of video decks and this is the first one I've come across with this kind of stupid fowlup. Maybe the manufacturer had a test bed for this during manufacturing but nothing in the way of test fixtures are called out in the manual. This is just plain dumb from beginning to end. These decks require calibration every so often and not providing the proper information causes problems and expense at the consumer end.
Personally, I don't like tossing something that should be repairable and useable for a good long time, obviously a lot of manufacturers don't view this as a plus, our throw away culture that has developed over the last 20 years is going to come back and bite us in a very bad way in the future.
I've got a lot of tube equipment which was designed and built to last, something most of the junk being peddled today can't do. I have equipment still working just fine that is 40, 50, 60 years and more old that will probably still be in use while the junk yard fills up with today's cheap trash, no matter how the PCBs are labeled.
I think we've made a lot of bad decisions in the name of cost and profit, they will come back to haunt us in a bad way.
Colorado Native--You have just indicated one huge problem in some manufacturing areas, at least in the appliance business;"beaners" are driving the bus. Cost accountants provide definite "value-added" but there are times when solid engineering must rule the day, especially when quality and safety are concerns and they are always concerns. One of the biggest problems we had a GE was substitution of parts when the part moved to low cost producers (LCCs). The qualification of vendors is difficult at best but when half way around the world it's really tough.
I'm surprised that most of the comments have missed the point. The assemblers did not have a problem. Putting part A from a bin marked A into every spot marked A on a board is a very reasonable assembly process. If every assembly works and never needs to be repaired, it is a way to possibly save money. But 100% yield and no repairs ever needed is an unlikely situation. Steve discovered the problem when he tried to repair a board with several 10K resistors all marked R1. If you want to measure the voltage on the 10K resistor at the output of a circuit, where do you put your probe? You have several different R1 choices and no way to tell the difference between them. You are then forced to trace the copper connections by hand to figure out which resistor is which, because the labels don't differentiate between them. This is an insanely expesive way to troubleshoot a board which is why component designators on a board are always (except at this crazy company) unique.
As a "greybeard" I've come across many poor design decisions that have much in common with this example. Any design decision is an attempt to solve a problem and is always a compromise between many competing tradeoffs. Poor decisions usually result from a "small-picture" view of the problem due to ignorance of the impact the decision might have somewhere on the "puchasing-manufacturing-end user" chain. In this case a slight improvement in the assembly process made troubleshooting almost impossible. A fact which the designer seemed blissfully unaware of.
The best one I've seen so far is a large board with NO designators or markings of any kind! I've seen this on really old boards, but this was something under 5 years old. I guess they decided to leave the silkscreen off to lower board costs. That one was a pain to troubleshoot from a schematic.
My guess is the lack of silkscreen was not a money saving decision, but one to make reverse engineering more difficult. Working on a board like this is not difficult with the "dolly sheet" in hand.
In fact, it is much easier to generate the "dolly sheet" (wow, after using it a few times I really dislike that term) than place reference designators in locations that are easily read after placement.
I worked at a company that used no silkscreen and only placed part numbers on schematics. The idea was to keep the design proprietary... and it meant you needed the schematic, BOM and "dolly sheet" to do anything.
If a product is not considered to be worth repairing then all of that labelig is a waste, since boards that don't function correctly may not be repaired anyway. It certainly does come down to the manufacturer's attitude about the whole product being worth repairing. This applies not only to really cheap consumer items, but also to quite expensive automotive electronics as well.
I have as most of us have, been the new guy. Sometimes a new perspective shines light on a bad practice. Keeping it to yourself, as I did and you did, does not always fair well. I know how it is to be the new guy and not rock the boat, but when things can be done better and safer, I wish it wasn't so hard to do. I finally did it and I got a lot of resentment for it. Was it worth it...not sure..I ended up quiting.
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