What is the proper name for this axial style fuse? - Page 1
Forum section: electronics / beginners

author: XOIIO
author_rank: Super Contributor
timestamp: July 20, 2015, 09:35:47 am
content: Got a pretty nice power supply however the fuse popped in it pretty shortly after testing it out, it is pretty old so I'm guessing it had gotten stressed a bit, (no way I drew 85 amps).Either way, it needs replacing, and I've never come across one of these that needed replacing so I'm not sure what the proper name for this style fuse is. I could not find my calipers, so there's a 1/4w resistor for scale. Axial mini fuse is the closest I can think of but those are much smaller.

author: krish2487
author_rank: Frequent Contributor
timestamp: July 20, 2015, 09:42:48 am
content: Thats not a fuse, its a Gas Discharge Tube (GDT).It is a more refined version of a PCB sparkgap.Have a look at littlefuse website. You should be able to find something there that is a replacement for this.

author: XOIIO
author_rank: Super Contributor
timestamp: July 20, 2015, 09:48:35 am
content: Quote from: krish2487 on July 20, 2015, 09:42:48 amAh alright, I figured it was along the lines of a mini buss fuse similar to the sand filled type for meters. I definitely will be replacing it with an identical part then. I'll just have to find those calipers and check out the site tomorrow.So they would go off voltage then and the listings are all in voltage, this power supply does have an option for 230v, so I'm curious how these are marked, unless 85 is the amperage that it will fail at. Considering I can't see any listings for amperage though I'm not sure.Also interesting that they have a set life before full failure, I guess it can work as circuit protection several times before failing completely.

author: helius
author_rank: Super Contributor
timestamp: July 20, 2015, 09:51:00 am
content: GDT is normally open, so there is nothing to "pop". They normally do not get damaged when activating to protect a device, but otherwise are similar to a MOV.

author: PA0PBZ
author_rank: Super Contributor
timestamp: July 20, 2015, 09:54:05 am
content: Quote from: XOIIO on July 20, 2015, 09:48:35 amIf you were thinking that it was a fuse and found it to be open... well, it is supposed to be. My bet is it's not even broken.

author: krish2487
author_rank: Frequent Contributor
timestamp: July 20, 2015, 10:11:36 am
content: And just a addition, forgot to put it in the earlier post.The 85 is not the A rating of the GDT.It is most likely a "minimum" breakdown voltage rating of the GDT and the 230 is the "maximum".I.E the GDT will trip in some units at 85V and certainly trip in ALL the units at 230V.Hope that helps you make a more informed decision.

author: XOIIO
author_rank: Super Contributor
timestamp: July 20, 2015, 10:22:59 am
content: Quote from: PA0PBZ on July 20, 2015, 09:54:05 amPossibly, I did read around 1 MegOhm on it, but there is a bit of charring on the bottom side, when I saw that megohm of resistance I figured it might not be a straight forward fuse, that or it didn't blow entirely. It isn't a massive amount of charring on the bottom, just looks like it overheated a bit, so maybe it is still fine and the proper fuse is somewhere less obvious. Might be prudent to replace it anyways though.

author: PA0PBZ
author_rank: Super Contributor
timestamp: July 20, 2015, 10:40:13 am
content: Quote from: XOIIO on July 20, 2015, 10:22:59 amIt will not hurt, but it will not solve your initial problem.

author: XOIIO
author_rank: Super Contributor
timestamp: July 20, 2015, 10:42:58 am
content: Quote from: PA0PBZ on July 20, 2015, 10:40:13 amYeah, I'll have to hunt down the fuse later, I need some sleep, and things are packed pretty tight on this board. Another things I noticed is the 5v 50a rail was at 5.6v, but I didn't have the sense terminals connected so maybe that is why. It died before I got a chance to test that.

author: PA0PBZ
author_rank: Super Contributor
timestamp: July 20, 2015, 10:48:56 am
content: Good night!

author: XOIIO
author_rank: Super Contributor
timestamp: July 20, 2015, 09:50:58 pm
content: Do'h, now that I've rested I feel like a moron lol, I don't know how I didn't recognize these from telephone equipment, they are for lightning strike protection, I've got a telcom panel in my garage with a few of these on it, got some nice boards with loads of relays out of it too.It's just a wee version.I gotta say that fuse is still hiding really well though, if it even has one, I mean surely it would... right? I doubt a power supply would pass regulations without one, especially since this uses screw terminal connections, maybe if it was in a rack it wouldn't need one but that would be bad design. Hmm.

author: PA0PBZ
author_rank: Super Contributor
timestamp: July 20, 2015, 10:05:52 pm
content: Take some pictures of the board so we can all have fun pointing to the obvious fuseI'm not sure it would have a fuse at the output though, most power supplies don't have one.They just measure the voltage at the output (crowbar) and the current, and fold back if anything is wrong.And of course it's not a problem, it's a challenge

author: XOIIO
author_rank: Super Contributor
timestamp: July 20, 2015, 10:20:56 pm
content: Quote from: PA0PBZ on July 20, 2015, 10:05:52 pmI figured it might be packaged like a resistor, but I couldn't see any so far that aren't actually resistors, I went to hook it back up in case it was a PTC that clamped down (although I did re-test it quite some time later) and the thing works again, I haven't checked the voltage output but it powers upMaybe a power surge did that, I have also been having some issues with one of my bench supplies at random (voltage changing on it's own, I have a video actually let me upload it, I haven't opened that thing up yet, it is a really nice old analog one though. I want to add nixie color backlights to the displays)But yeah the thing seems to be powering up fine now, so who knows.Here are pictures of the board, not exactly great quality from my phone and I only have one light I was able to try and light the board up with properly. I'm still going to go over every resistor style thing in there that I can see to find a fuse.Yes, I did make sure to reconnect that resistor and that to-220 package before powering it up, that wouldn't have caused it though as it died when it was all sealed up with a warranty sticker. (left it closed up while it sat for a while in case it was a PTC as well.)Unfortunately I don't know where a couple of the big arse sand filled fuses from a big APC supply are, otherwise I would have tucked one in there as a joke lol. It is really odd that there isn't anything that is obviously a fuse, I beeped my way around the AC input lines and nothing for protection aside from that gas discharge tube and a diode.

author: XOIIO
author_rank: Super Contributor
timestamp: July 20, 2015, 11:02:20 pm
content: Here's that power supply issue, like I said I have yet to even open the thing up, I'm in the middle of trying to organize everythinghttps://youtu.be/2UUoRw-Vnak

author: XOIIO
author_rank: Super Contributor
timestamp: July 21, 2015, 07:16:03 am
content: Well, it's dead again, the fan occasionally tries to spin up but fails, what the heck.I'm gonna have to wait till I clear off some desk space before I can probe it with the power on, right now it would probably fall into my lap. This should be "fun" to figure out though.