A hair away from boom, or what concerning stuff you found inside devices? - Page 1
Forum section: electronics / general

author: Artlav
author_rank: Frequent Contributor
timestamp: November 22, 2016, 08:11:49 pm
content: I recently bought a 24V to 12V converter. It turns out the output was 13.5V, which is a bit too high, so i changed the resistor divider, and was trying to track the undervoltage lockout issue that this produced.As i pocked the circuit with the continuity probes, i saw something that looked like a bodge wire.Except it didn't really made sense to put one there - it connected the 24V input with the IC's 10.5V regulated input.As i tried to probe it, it wasn't actually conducting unless touched.The whole board was conformally coated, so what this "bodge" actually was a naked copper hair with the micron-thick conformal coating layer between it and the pads that would cause the thing to go boom if connected.Good thing i had to change that voltage...So, what disasters waiting to happen have you found inside your newly bought stuff?

author: Ampera
author_rank: Super Contributor
timestamp: November 23, 2016, 07:03:41 am
content: Probably inside my own creations. There used to be a post with "Your finest bodge" a while back, probably could find it if you went looking.My dad has a 230 to 115v step down converter he made by literally taking a case with a Shucko in/out that contained (Idk if it was a power filter or what) something, plopped a big o'l power transformer in, and wired it up. He might have had a fuse, but yea....Probably my worst instance of this was a close call with an 80486 gaming PC I was building, stuck the board in the case, and was spending 3 days trying to figure out for the life of me why it wouldn't test memory.As it turned out there was a standoff I had in the case literally making contact with the board, and not only that a built in, un-removable standoff was ALSO touching the board. Yeap, glad it's ticking fine now, or that would have been 90 bucks down the friggin drain, not to mention a load of time while it stumbled its way to the US from Russia.Check out Big Clive, he has all sorts of embarrassing shugar from Chinese tat.

author: Muttley Snickers
author_rank: Unknown
timestamp: November 23, 2016, 08:49:16 am
content: My big arse arc welder, a quality name brand which I purchased new and have had for many years but only used occasionally, on a rainy day recently for no given reason I decided to open it up and have a look inside and found just about every screw loose including all the electrical connections, I applied Loctite to all of the fixings and connection screws and avoided a potential catastrophic event, I deserved a medal for that one but didn't even get a pat on the back.

author: Halcyon
author_rank: Unknown
timestamp: November 25, 2016, 12:55:08 am
content: As a young computer repairer, I once found a dead mouse inside the case of a customer's computer. It had been there that long that it was more dehydrated rather than rotten. It wasn't large, just small enough to squeeze through the rear I/O slot holes.

author: BradC
author_rank: Super Contributor
timestamp: November 25, 2016, 01:16:41 am
content: Quote from: Muttley Snickers on November 23, 2016, 08:49:16 amI heard a great quote the other day that said basically anything from China should be treated as a kit which is supplied completed purely for shipping convenience. The first thing I do when I get a new bit of cheap tat is disassemble it, check it over and re-assemble with threadlocker. Also replace all the bearings as a matter of course.

author: SeanB
author_rank: Super Contributor
timestamp: November 25, 2016, 06:24:01 pm
content: With the arc welder is is very likely the screws were all tight originally, but have loosened from both the thermal cycling of use and the vibration of the transformer and wiring under current.OTOH I had a Chinese box where I had to get out the hex bit and the socket set as well, to persuade any of the screws holding the case together to come out at all. they were all tightened up to just short of stripped.

author: VK3DRB
author_rank: Super Contributor
timestamp: November 26, 2016, 11:59:49 am
content: Quote from: BradC on November 25, 2016, 01:16:41 amI have a mate who imported a shoddy Chinese made milling machine from Hare and Forbes. Rather than turning it on, the first thing he did was tear it down, replace all the Chinese bearings with qaulity Japanese bearings, clean out all the swarf, and rebuild the machine with some improvements. He also added his own design electronics, stepper motors, and some software so he would port a Solidworks design onto his CNC controlled milling machine. In the end, it was a work of art. Not bad for a 70 year old retired engineer!

author: Artlav
author_rank: Frequent Contributor
timestamp: November 26, 2016, 04:42:19 pm
content: Quote from: BradC on November 25, 2016, 01:16:41 amAh, that reminds me of the accident that got me into a habit of doing the same.I once bought a cheap variable PSU.Goes from 0 to 30V, 0 to 5A. Nothing complicated enough to screw up, you would think?It worked fine, but something was rattling inside.So i took it apart, and there was a loose screw in there. Metal screw among sparsely insulated boards and wiring.

author: SeanB
author_rank: Super Contributor
timestamp: November 27, 2016, 09:50:04 am
content: Quote from: VK3DRB on November 26, 2016, 11:59:49 amChinese production equipment, I have been slowly replacing the wear parts from the cheapest material they could buy to more durable ones. However, some parts I have never been into, so the original grit and polish residue is still in there. One thing I am slowly buying is a full set of adjustable reamers as I replace bushings, as I always deliberately make the replacement parts both oversize on the outer diameter and undersize by 1mm, so I can get a better fit to the shafts than sloppy like the original fit. Does mean an hour or more of work per hole getting the fit correct, but worth it in consistency. Vesconite Hilube is also a lot better wearing and a heck of a lot cheaper than bearing bronze as well, especially in larger pieces.However with the one thing, as it arrived I was not happy at all with the power cable, as it arrived with a Chinese plug on it, and the cable was that lovely thin stuff, with 3 green, white and pink cores in it. Took off the cover, and found the wiring scheme was white for ground, pink for line or neutral (double pole switch) and green for line or neutral, and the cable restraint was simply a knot in the 3 wires ( not the sheath) to hold it in the bare hole cut in the metal case. 20mm hole saw and a proper cable gland later, and the nasty cable was replaced with a donor, made by taking an old IEC power cord and cutting the IEC end off it. Had plenty of those around, as every computer came with one, and I put in dedicated sockets for them and needed the right cables instead.