Is a lifted track safe? Mains in-line bathroom fan - Page 1
Forum section: electronics / repair

author: HobGoblyn
author_rank: Unknown
timestamp: January 13, 2023, 02:55:06 pm
content: Hi, repaired my in-line fan, the big resistor is soldered to the track fine but the track has lifted.I’ve superglued it back down the best I can, resoldered the resistor, the track doesn’t appear damaged, just lifted.Am I right to presume this is safe?Sorry for pics, taken through microscope with my phoneThanks

author: Grandchuck
author_rank: Super Contributor
timestamp: January 13, 2023, 03:25:49 pm
content: Resistor heat caused it? Should be OK. How does the resistor look?

author: Swake
author_rank: Frequent Contributor
timestamp: January 13, 2023, 03:27:34 pm
content: From a liability perspective no-one will tell you this is safe. So I tell you it is not safe.What would I do based on the information in the pictures? Clean/scrape a little more of the green protective film from the track and tin it with an extra layer of solder to reinforce it and ensure it is 'fat' enough. Eventually I apply some kapton tape for isolation because there are a lot of electrons flowing over there.I would also put back the caps on the left side of the board in picture 2 else it's gonna be another surprise

author: coppercone2
author_rank: Super Contributor
timestamp: January 13, 2023, 03:45:54 pm
content: I think you want like JB weld or something that can take the heat a little better then super glue

author: DavidAlfa
author_rank: Super Contributor
timestamp: January 13, 2023, 04:13:43 pm
content: It won't move anywhere unless receiving some serious beating, which will probably destroy the entire device.A blob of epoxy or silicone will fix it in place.

author: HobGoblyn
author_rank: Unknown
timestamp: January 13, 2023, 04:18:24 pm
content: Quote from: Swake on January 13, 2023, 03:27:34 pmYep, done that, they’re the 2 caps you can see in pic 3

author: HobGoblyn
author_rank: Unknown
timestamp: January 13, 2023, 04:21:04 pm
content: Quote from: Grandchuck on January 13, 2023, 03:25:49 pmhttps://www.eevblog.com/forum/repair/in-line-bathroom-extractor-resistor-overheating/msg4580755/#msg4580755

author: Ian.M
author_rank: Super Contributor
timestamp: January 13, 2023, 04:50:45 pm
content: Its not safe, as continued vibration from the fan motor could fatigue the track along the board edge till it cracks, with a subsequent risk of arcing and fire due to the motor current.High temperature unfilled epoxy suitable for reattaching PCB pads for a minimally visible professional repair is very expensive and difficult to find except from specialist suppliers in quantities larger than any DIYer would want, and only forms a reliable bond with a scrupulously cleaned and prepared board surface and copper foil that has been specially prepared for epoxy bonding.A proper repair would involve drilling out the holes for both ends of the big dropper resistor, and setting hollow brass rivets through them to put the resistor legs through to re-anchor them to the PCB.A somewhat acceptable bodge repair would be to scrape and tin the edge track and solder a tinned wire along it near the resistor pad to reinforce it, clean and tin the whole pad, drill two holes either side of the pad at its edges, the same distance from the board edge as the resistor hole, then wrap a bare tinned copper wire a single tight turn round the resistor leg topside, take both ends through the new holes, with sharp bends so the wire is tight against the PCB on both sides and solder them to the pad to lock the resistor leg in place. Also solder the turn round the leg topside.

author: HobGoblyn
author_rank: Unknown
timestamp: January 13, 2023, 05:10:31 pm
content: Thanks, if I can’t get a new board I’ll fork out for a new fan. Especially as it’s in the attic.Edit:https://jharries.co.uk/product/manrose-tdi-replacement-timer-board/1760?gclid=EAIaIQobChMIwpGnxIXF_AIVRrLVCh3kugUoEAQYAyABEgJHVfD_BwEBetter than £100 for the entire thing

author: Gyro
author_rank: Super Contributor
timestamp: January 13, 2023, 06:56:35 pm
content: That's long been a ridiculous board design. There's absolutely no reason why they couldn't have provided a much bigger copper area for that resistor lead, as the have for the other end.Good to see that you've managed to find a replacement anyway, filed for future reference. I recently had to repair one with a shorted electrolytic capacitor (voltage rating too close the the zener voltage).

author: james_s
author_rank: Super Contributor
timestamp: January 13, 2023, 06:59:05 pm
content: I don't see any problem with it, lifted tracks are very common with cheap phenolic PCBs like that, I've dealt with it many, many times. I would not hesitate to just keep using it.

author: Ian.M
author_rank: Super Contributor
timestamp: January 13, 2023, 07:09:57 pm
content: Certainly, if all it could do if it comes unglued then fatigued due to vibration, was to break the low current circuit to the dropper resistor, as that would simply disable it. However, I expressed my concern above that it might peel further and fatigue and eventually break that track along the board edge, between the three way and two way terminal blocks, which I suspect may carry the motor current.If I was tempted to bodge it without securing the pad, I would at least add a mains rated jumper wire between the two terminal blocks so a crack in the edge track cant arc.

author: DavidAlfa
author_rank: Super Contributor
timestamp: January 13, 2023, 07:12:48 pm
content: Simply take a solid copper wire on top of the trace, soldered to these 3 pads, with a decent blob of solder to make it strong.

author: james_s
author_rank: Super Contributor
timestamp: January 13, 2023, 07:20:14 pm
content: If there is enough vibration to cause the PCB to fail then that seems like a fault with the fan, my bathroom vent fans are a different design but they don't vibrate. Adding jumper wires is easy, I also typically scrape off a bit of the solder mask around the joint to increase the area of the joint for mechanical strength. A blob of silicone to secure the component can help too. I'm surprised at the number of people saying to replace the board, this looks like a trivial repair.

author: Gyro
author_rank: Super Contributor
timestamp: January 13, 2023, 08:18:04 pm
content: There are a couple of other threads relating to this fan PCB, one from the OP and another, earlier one. I suspect that the track lifting was actually due to soldering heat on the already thermally degraded track adhesion...https://www.eevblog.com/forum/repair/in-line-bathroom-extractor-resistor-overheating/https://www.eevblog.com/forum/chat/uk-toilet-extractor-fan/I agree that the soldering a single core wire between the three solder points on the track would be a satisfactory repair, preferably taking a turn around the resistor lead stub for extra security and joint integrity. Yes, the track does carry motor current but it is no more than 15-20W @240V. I would however caution against adding Silicone, glue etc. or anything that might potentially alter the flamability of the assembly. It sits under constant thermal dissipation in a roof space.

author: HobGoblyn
author_rank: Unknown
timestamp: January 13, 2023, 10:38:03 pm
content: Thanks all.If it wasn’t sitting in a pretty hard to get to part of my attic, I would run the single core copper wire as suggested.But for £21.35 delivered, for peace of mind, I’ll buy the board.

author: vk6zgo
author_rank: Super Contributor
timestamp: January 14, 2023, 12:20:10 am
content: For that much, you could go much of the way towards buying a new fan.Why is it so complex? --The fan in my (separate) toilet just uses a plain old synchronous motor running direct off the 230v Mains supply.I bought one cheaper Chinese one, to replace the (failed) ancient Oz one in the dunny, which was still the conventional kind, but one of the "bean counters" in the dear old PRC decided to replace the phosphor bronze bearings used in the old one with "plain old brass", so it lasted just over a year, till I had to replace it with a more costly one (still from the PRC), which used ball bearings.With ball bearings & a uncomplicated synchronous motor, the new one will probably outlive me!

author: themadhippy
author_rank: Super Contributor
timestamp: January 14, 2023, 12:27:45 am
content: Quoteso there not running 24/7,instead they run on for a few minutes after there switched off to continue shifting the smell/condensation.However there biggest drawback is often there wired to the lighting circuit so come on when you switch the light on ,not very useful during the day

author: james_s
author_rank: Super Contributor
timestamp: January 14, 2023, 12:40:22 am
content: Are fan timers not a thing there? The vent fans in my bathroom are controlled by a timer mounted next to the switch for the light. Most are mechanical clockworks, you turn the dial up to 10 minutes or whatever and it winds the spring that runs down and then switches off. Some are electronic, push a button for the number of minutes you want the fan to run. The fan itself is just a motor that operates from line voltage.

author: vk6zgo
author_rank: Super Contributor
timestamp: January 14, 2023, 04:08:31 am
content: Quote from: themadhippy on January 14, 2023, 12:27:45 amOurs don't run "24/7".They are switched on & off with the light.Most toilets are a bit dark, so even during the day, the light is useful.A timer would be nice, but is hardly essential, unless your toilet adventure is really eye-wateringly extreme.Back in the day, toilets in hotel & motel rooms often used a timer which was actually a switch with a delayed off function performed pneumatically---they looked funny but worked well.The toilet usage in such places is a bit different to in the home.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: January 14, 2023, 04:23:10 am
content: Quote from: james_s on January 14, 2023, 12:40:22 amWhat I've done is install the small, fairly cheap flush mount IR sensor. Connect to fan and light or just the fan. Dial the time delay up to somewhere decent. What that does is run the fan when someone visits and runs for a time afterwards.Recommend connecting the light to it as well. They have a light sensor with an daylight adjustment so once all that is setup, anyone can just concentrate on the job at hand.

author: Gyro
author_rank: Super Contributor
timestamp: January 14, 2023, 08:09:32 pm
content: Runback mechanical timers and pneumatic delay switches, reliable as they were (and probably still are somewhere), make the dropper resistor and 4000 series IC + triac approach seem positively 21st century!Yes, PIR sensor fan (and light) controls are becoming more common domestically. They have been fairly common in commercial settings for a couple of decades. I remember being called out once to the office, in the very early hours of the morning, by the alarm company. When I arrived, I cautiously let myself in and was walking through the downstairs lobby area when I heard the fan in the men's toilets start up... Oh Sh*t, they're hiding in there and the windows are barred! It took me a good 5 minutes of standing there, spanner clutching and in digestive distress, to notice that the contractors had fitted the PIR sensoroutsidethe toilet entrance!It shook me so much that it was the only occasion that I went back to reception and phoned for the local beat officer to back me up while I searched the rest of the building. It turned out that when we had been working late the previous evening, somebody had opened a window and a large moth had got in. It laid low and then got bored and got friendly with one of the alarm PIRs, a bit of an embarrassing conclusion when you have the law accompanying you.

author: coppercone2
author_rank: Super Contributor
timestamp: January 14, 2023, 09:33:22 pm
content: I got a few bags of brass PCB rivets a while back that accomodate power electronics leads so I can do these kinds of repairs with peace of mind