Electronics GOOF UPS you've seen - Page 1
Forum section: electronics / general

author: lordvader88
author_rank: Frequent Contributor
timestamp: December 28, 2016, 04:38:47 pm
content: I've not seen many since I'm pretty new to this (probably only 1). But looking at a multiband radio I own, on the PCB its clearly marked D11 and with the diode symbol on it, but they have 1k resistor there, it seems to follow from the antenna. Perhaps I'll upload the picture later.I also own a plasma globe that I don't think ever worked until I 1-2 years later I opened it and a 470uF cap was missing but clearly marked out on the PCB. Later that and a AC-DC mod later, and I did get working (I have question for another thread about that thing tho)

author: elecman14
author_rank: Unknown
timestamp: December 28, 2016, 05:59:49 pm
content: The part that is missing may or may not be a goof up. If a manufacturer thinks they can get away with it they may not populate all the part locations. It is easier to add a part to the PCBA if needed, if there is a spot for it. They also may use that PCB in multiple products. Depending on how the PCB is populated.

author: KhronX
author_rank: Frequent Contributor
timestamp: December 28, 2016, 06:25:38 pm
content: In fact, the "Chinese" way to manufacture at least switching power supplies is, copy a good / robust design, remove parts one by one until it doesn't work anymore, and put the last one backOr at least so i've heard...

author: dmills
author_rank: Super Contributor
timestamp: December 28, 2016, 06:40:54 pm
content: If that is the way it is done, then they learned it from the Americans, specifically one Mr Muntz seehttps://en.wikipedia.org/wiki/Madman_Muntz#Muntz_TVMy suspicion is that reality is more nuanced in that you can buy switchers at various price points where the only difference is the BOM cost, and having a common PCB saves cost when running those sorts of volumes.Regards, Dan.

author: Benta
author_rank: Super Contributor
timestamp: December 28, 2016, 07:19:15 pm
content: Here's the Bob Pease (one of my heroes) take on "Muntzing":http://electronicdesign.com/boards/whats-all-muntzing-stuff-anyhowApart from that, it's entirely normal to find unpopulated places on a PCB. Try opening an old VCR.Every market has its own needs, voltages, signals etc. and partially populating a circuit board is seen all over.

author: German_EE
author_rank: Super Contributor
timestamp: December 29, 2016, 02:52:21 pm
content: A Device that used 8 x 110V fans that also needed to be wired for 110V/230V operation. So on 230V they took four fans, wired them in parallel, then joined them to another block, something like this:L...........|110V FAN|................|110V FAN|.............................N|110V FAN| |110V FAN||110V FAN| |110V FAN||110V FAN| |110V FAN|See the problem? Suppose one fan fails short circuit, it immediately stops three other fans from working and, as a bonus, applies 230V to four of the remaining 110V fans. This little gem was discovered on an elevator controller by yours truly and I won a substantial reward for finding it.

author: SeanB
author_rank: Super Contributor
timestamp: December 29, 2016, 03:40:11 pm
content: I had a similar thing. Otis used a 3 phase circuit breaker to provide overcurrent protection on the retiring cam and the brake, using one pole of the breaker to do the protection, and one of the other poles to break the safety circuit. Used because a 3 phase breaker is a lot cheaper than a single phase breaker plus auxiliary block, or a single phase isolator. Now it worked fine, but would trip on the near top floor if you ran down, then went back up immediately. Measured the current and it was 6A, on a 5A breaker. So, stop half way up or down, or do it again going up, and it would not get enough thermal load to trip. Would not do it either till you did the full travel 2 times immediately, so was a fault not found in commissioning, only showed up a week later in hot weather.My solution was to draw a quick modification on a piece of cardboard, from a relay box, showing the modified circuit diagram for the ladder logic, and gave it to the tech to take past the installation engineer. Next afternoon he was back , with this cardboard now laminated into a plastic sheet, signed and approved by the engineer, to be included into the diagrams for this lift in the pocket in the motor room. Still there as far as i know, with the installed jumper to separate the load into 2 3A loads that I cut and installed there as well.I also had to explain to the Technician the difference between 180 and 320 V varistors, and why the 180v ones would occasionally explode when used in certain motors and brakes, which did not use a rectified and unsmoothed 115VAC supply, but used a 220VAC supply instead.Should have done that lift mechanician training I was offered once, I like riding above the car in the shaft.