VCR Teardown: apparently Orion manufacture WTF moments. - Page 1
Forum section: electronics / general

author: cprobertson1
author_rank: Frequent Contributor
timestamp: February 20, 2014, 03:10:29 pm
content: So I was tearing down an old VCR I found in the loft - and apart from finding more gears than you program a stick to shake at, I found this bizarre little blob of solder full of SMD resistors*Apart from that I also found a little serrated-edge of solder on the border of the mains voltage section.any ideas?*I thinkCan anybody tell me what these are... and why on earth there is a blob of resistors?Attatchments:1- Resistor-blob2- Resistor-blob - seriously... why3- Resistor-blob - seriously... why... wtf...?4- Serrated solder near mains voltage section5- Is that an inductor/choke? (10mm grid on background)(there are a large number of inductors in the product; but this particular component is unique on this particular board (marked as L17 incidentally - other inductors were also designated with an 'L'))

author: sacherjj
author_rank: Frequent Contributor
timestamp: February 20, 2014, 04:28:18 pm
content: There was only a pair of resistors when that was made, but they breed like rabbits.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 20, 2014, 05:26:59 pm
content: I didn't know components could metastasize...I would have to guess, some of those MELF components rolled loose (they're supposed to be glued down on assembly, before soldering), and just happened to glom onto that point. What is it, the mounting terminal of a metal can or something?That type of circuit is wave soldered, so.. if they came loose, they could kind of just end up anywhere I would think, most likely not on the board at all?Cheers to QC in any caseAs for the inductor, yes, that's an inductor. Probably a small one, a few uH and 100mA or something?The serrated traces are intentional breakdown spots. I don't know the regulatory significance of them; I've seen this a few times before (a Meanwell power supply I've taken apart, for instance). Obviously for transient arresting, but creepage breakdown across PCB is poorly controlled at best (might be 3-10kV?), it hardly seems worth it.Tim

author: owiecc
author_rank: Frequent Contributor
timestamp: February 20, 2014, 05:46:31 pm
content: Some spare resistors with a bit of free tin. Designed for serviceability

author: MatCat
author_rank: Frequent Contributor
timestamp: February 20, 2014, 05:52:04 pm
content: Who says you can't make modern art on a production PCB?

author: cprobertson1
author_rank: Frequent Contributor
timestamp: February 20, 2014, 07:25:55 pm
content: It really is weird xDForgot to mention (though as T3sl4co1l said) it is indeed wave soldered so how on earth it can end up there is beyond me. I've since removed it and counted no less than 9 resistors stuck to the pins of two caps: maybe it came off a previous board and ended up getting globbed onto this one? really does seem weird!Thanks for the inductor- and breakdown-spots- answers incidentally: I'm technically still a nubNot seen that particular inductor package before nor the breakdown points xD

author: free_electron
author_rank: Super Contributor
timestamp: February 20, 2014, 08:10:19 pm
content: it looks like the wave soldering machine collected some parts earlier and they clumped together and were deposited on the joint.since the vcr passed final test it was not detected. ( no optical inspection )the serrated edges are for hipot testing.apply high voltage and it flashes over there protecting the rest of the system. there should be three of those tructures.one from each live wire to ground and one between the live wires. they are typically found before the entry filter and or common mode choke in the witching regulator. one of the sides should be connected to a screwhole to touch the metal chassis of the machine

author: chicken
author_rank: Frequent Contributor
timestamp: February 20, 2014, 10:19:36 pm
content: An SMD Flux Capacitor of course