Retroensafetying a mains-powered device - Page 1
Forum section: electronics / repair

author: 5U4GB
author_rank: Super Contributor
timestamp: March 01, 2024, 09:49:29 am
content: I've been asked to look at a mains-powered device, almost certainly from the Middle Kingdom, which while it passes some cursory checks (case is earthed, fused, etc) has had some steps skipped during the assembly process:Just... bare wires. It looks like it's going to be a serious pain to get out of its case to solder in insulated wires with boots to cover the switch contacts, would some liquid electrical tape be sufficient here? I'm not going for UL certification, just something safer than what's there at the moment.

author: Ian.M
author_rank: Super Contributor
timestamp: March 01, 2024, 10:48:03 am
content: Why do you think insulated wires will improve safety? A mains PSU PCB typically has plenty of exposed mains or high voltage DC component leads and a PCB mounted IEC inlet is no different. Make sure a user cant gain access to the PSU without tools by fitting tamper-resistant case screws, and if not present add a sticker "No user-serviceable parts inside"

author: 5U4GB
author_rank: Super Contributor
timestamp: March 01, 2024, 11:17:05 am
content: Quote from: Ian.M on March 01, 2024, 10:48:03 amI wasn't worried about the IEC inlet, look at the switch next to it.

author: Zero999
author_rank: Super Contributor
timestamp: March 01, 2024, 11:38:28 am
content: Quote from: 5U4GB on March 01, 2024, 11:17:05 amIs it a mains switch? If so, I don't see the problem with it, as long as it's suitably rated. As mentioned above, so long as it's entirely enclosed and the user can't touch it, then it's not a safety concern.I would be concerned if it was switching the DC side, because it's close to the mains connector, but that doesn't appear to be the case.

author: 5U4GB
author_rank: Super Contributor
timestamp: March 01, 2024, 10:04:33 pm
content: It's a mains switch and suitably rated, it's just that years ago I would have been dinged if I hadn't used insulated wire with a crimped on... probably insulated spade lug for the switch connectors, thus my slightly allergic reaction to first seeing it.So it's perfectly OK to connect a switch carrying mains voltages like this?

author: Ian.M
author_rank: Super Contributor
timestamp: March 01, 2024, 10:13:24 pm
content: In proximity to other touch hazards, and protected from general access, yes. Somewhere where the end user might contact the back of it doing routine maintenance etc. *NO*!I'd be more worried about the switch becoming dislodged or if its really cheap and nasty, its rocker popping out exposing live contacts. The former can be fixed by a suitable adhesive sealant to prevent its locking ears geting pushed in, but the latter would need replacement with a good brand of switch, at which point you might as well do it properly, though it looks like it would be possible to re-do its PCB connections from the top side, taking care not to add too much solder.

author: 5U4GB
author_rank: Super Contributor
timestamp: March 01, 2024, 10:45:58 pm
content: From the quick look I've had so far the rest of it seems to pass muster, very solidly built, hex head bolts alongside the Philips screws to discourage casual opening, plenty of heatsinking, and it's being used by an adult who's unlikely to mess with it. I just got an allergic reaction from the bare wires, but it's good to know it was unwarranted.