When thread lock runs out at factory... - Page 1
Forum section: electronics / repair

author: FireFlower
author_rank: Regular Contributor
timestamp: June 20, 2018, 09:22:34 am
content: Product:http://webshop.caliber.nl/products/view/details/bc108us.htmlThis unit is not too badly broken, just need to give it a bang and it usually starts playing. Probably there is a contact issue inside but who uses epoxy on the screws?

author: mariush
author_rank: Super Contributor
timestamp: June 20, 2018, 09:38:29 am
content: That black stuff may be the kind of material that becomes slightly conductive with age, as it dried out.I would scrape it everywhere it covers solder joints or contacts, as there may be low resistance paths between component pins or solder points.

author: amyk
author_rank: Super Contributor
timestamp: June 20, 2018, 11:31:19 am
content: I'm not surprised given that it's going to be subject to a lot of vibration in its intended use-case.Is it a somewhat soft, silicone-type compound or really rock-hard epoxy? If it's the latter, then they did screw up.

author: stj
author_rank: Super Contributor
timestamp: June 20, 2018, 12:57:56 pm
content: i have seen stuff that looks like that that had a flexable polymer type feel to it - you could pull bits off with pliers.

author: FireFlower
author_rank: Regular Contributor
timestamp: June 20, 2018, 01:45:13 pm
content: Quote from: amyk on June 20, 2018, 11:31:19 amRock hard epoxy

author: stj
author_rank: Super Contributor
timestamp: June 20, 2018, 06:22:00 pm
content: then it's potting compound probably.

author: Synthtech
author_rank: Regular Contributor
timestamp: June 20, 2018, 08:01:11 pm
content: Behringer?

author: FireFlower
author_rank: Regular Contributor
timestamp: July 15, 2018, 05:56:17 pm
content: Finally fixed this one... taking off hard epoxy was hell... had bake pcb in oven at 180C, then cut and scrape off epoxy...And I only had to fix the damn speaker itself (speaker to terminal connection was not soldered properly)....Well at least everything is now soldered more or less properly, insulation has been taken care off, added thermal compound for power fets/transistors...

author: james_s
author_rank: Super Contributor
timestamp: July 16, 2018, 01:41:17 am
content: That is unusual, I've seen wax, adhesive that resembles "Shoe Goo", and various paint/lacquers used but I don't think I've ever seen epoxy potting compound used as threadlock. Maybe they had some leftover from potting a run of something else and just decided to use the same stuff?

author: CatalinaWOW
author_rank: Super Contributor
timestamp: July 16, 2018, 03:30:25 am
content: More likely someone in purchasing found a discount and had a "gunk is gunk" mentality. Early in my career I had a battle with a buyer over why a really cheap 2N2222 knockoff could not be substituted for the power output transistors in one of our products. He had checked and found they were fully compatible (NPN and three terminals). He literally asked me "transistors and transistors aren't they?"I had to bring in my boss to help. I was an engineer and knew what I was talking about, but had no seniority or purchasing authority so only roughly balanced the decision power of the buyer.

author: james_s
author_rank: Super Contributor
timestamp: July 16, 2018, 04:06:36 pm
content: I would have been tempted to just say "Sure, if you say so" and just make sure it was known who made the decision to substitute those transistors when the whole production run fails.