Don't do this to your Fluke fuses or any other fuse - Page 1
Forum section: electronics / testgear

author: retiredcaps
author_rank: Super Contributor
timestamp: September 16, 2016, 08:13:10 pm
content: Modemhead pointed me to this 5 minute video for the ohms not working repair part and I decided to share because of the fuse part. Don't do this to your fuses.At least the plastic white shield did its job.I don't understand why someone, not Tomislav, would do such a modification to the fuse. Too cheap to buy a new one?I too bought a multimeter, an used Fluke 87, where someone put in a threaded screw in place of the 10A fuse.Tomislav Darlic said he would use this repaired Fluke 175 is in car. Nice meter for the car!

author: Muxr
author_rank: Super Contributor
timestamp: September 16, 2016, 09:28:21 pm
content: Yeah, that's not a good idea.Definitely a nice meter, I'd use it.

author: Faith
author_rank: Unknown
timestamp: September 17, 2016, 05:29:43 am
content: Really?

author: Brumby
author_rank: Unknown
timestamp: September 17, 2016, 05:44:01 am
content: Not to HRC fuses, but I did do something like this to a glass fuse once.Sunday night - at a venue. Somebody was being stupid with the sound gear and blew a speaker protection fuse. Didn't have the right fuse on hand, nor one that could substitute and no time to go anywhere - so I peeled out a strand of a similar gauge from some wire I had and soldered it in place (properly, that is - inside the tube). That was an anxious night and I was watching both the people and the gear like a hawk.It was replaced with the right fuse the next day..... but to bridge an HRC fuse like that...? Good grief NO!

author: Muttley Snickers
author_rank: Unknown
timestamp: September 17, 2016, 05:54:33 am
content: After seeing the video my concern would be with what else the previous technician took liberty or shortcuts on out in the field, the fact that a multimeter was part of the required tool kit would indicate that they perhaps worked on either electronic or electrical systems and going by the incurred damage to the meter I suspect the later.Even if the bodged fuse was a temporary repair to get the technician out of trouble and finish a job the meter should have been tagged as not in service and a supervisor notified of the current status with the offending fuses removed, just leaving it in that state for the next person to pick up and use is inexcusable.This is another reason to carry a couple of meters in your tool box particularly if working out in the field or remote locations, if you blow one up then ok possibly a bad mistake but if you blow up another in the same circumstances then it’s probably time to take a good hard look at your skill level and competency.

author: testmode
author_rank: Regular Contributor
timestamp: September 17, 2016, 06:51:47 am
content: Reminds me of a quote my friend always used to say - "Little knowledge is dangerous."

author: raptor1956
author_rank: Frequent Contributor
timestamp: September 17, 2016, 07:07:00 am
content: There are stories of a guy that blew a fuse in his car back when fuses were of the older design and since he did not have any fuses to replace it but he did have some 22 ammo, yes, this was the USA I believe, he pushed a round of 22 ammo into the fuse holder and was promptly shot by it. I do believe this is an urban legend, though there are people that would in fact do this. I'm not sure I see a way for the ammo to cook off though it's not 100% impossible. But, even if it did cook off I'm not sure how he would have been hit by it but, once again, not 100% impossible.Brian

author: testmode
author_rank: Regular Contributor
timestamp: September 17, 2016, 09:24:17 am
content: Quote from: raptor1956 on September 17, 2016, 07:07:00 amI could only imagine the guy probably had that action-mode look when loading in the ammo in the fuse holder. Like lock 'n load! Funny but sad at the same time if it actually happened in reality.

author: Fungus
author_rank: Super Contributor
timestamp: September 17, 2016, 09:33:07 am
content: Quote from: raptor1956 on September 17, 2016, 07:07:00 amMythbusters did it.Short version:a) Yes, you can get the bullet to fire.b) No, it's probably not lethal because bullets are designed to be enclosed in a long tube.http://www.discovery.com/tv-shows/mythbusters/videos/gun-cartridge-fuse-minimyth/

author: Rolo
author_rank: Regular Contributor
timestamp: September 17, 2016, 09:59:49 am
content: These fuses are expensive but that's what you accept when buying the meter. I have spares for all fuses in my multimeters (Fluke and Metrahit) so I am not tempted to do this kind of "fixes".

author: Cerebus
author_rank: Super Contributor
timestamp: September 17, 2016, 04:25:36 pm
content: Quote from: Rolo on September 17, 2016, 09:59:49 amDitto here.My Fluke 25 has a nice feature. On the 10A range it's just got the usual beefy 15A HRC fuse but on the mA range it has a beefy 3A HRC fuse but it has a 650mA glass fuse in series with it. Thus in the event of momentary stupidity (measuring volts with the probes still in current setup) the cheap easily replaced glass fuse blows but in the event of an overload that is beyond the breaking capacity of the glass fuse the HRC fuse steps in to sacrifice itself. I suspect the reason that this isn't in place across the whole Fluke range is availability of space - the 25 is big and hefty enough that in the event of a dispute about who's right about a measurement you can use it to batter your opponent to see things the Fluke 25's way.

author: Sonny_Jim
author_rank: Unknown
timestamp: September 17, 2016, 06:53:28 pm
content: Seen this 'fix' many, many times when I used to work as a pinball tech. Ranged from a piece of wire across the fuse, wrapping the fuse in tin foil or just jamming a screw in instead of a fuse. The record was one machine were I found13fuses all with a wire wrapped around them.Special bonus image:You can see more horrible 'fixes' I've found here:http://pinwiki.com/wiki/index.php?title=What_is_a_%22Hack%22%3F

author: joeqsmith
author_rank: Super Contributor
timestamp: September 17, 2016, 07:43:44 pm
content: Quote from: Sonny_Jim on September 17, 2016, 06:53:28 pmWow. Some nice solder work in some of those photos.

author: SeanB
author_rank: Super Contributor
timestamp: September 17, 2016, 08:05:07 pm
content: Would be hard to improve, short of using a guy with both myopia, advanced Parkinsons and giving him a gas torch and some solder bars.

author: David Hess
author_rank: Super Contributor
timestamp: September 17, 2016, 09:23:10 pm
content: These fuses can be very expensive because they are designed to block high voltage DC and management is not always so enlightened as to allow spare meters or fuses.I have soldered a jumper across these special fuses before but always looked up the proper wire size usually resulting in taking a single strand of 32 gauge wire (10 amp fusing current for 1 second) from a length of 24 gauge 7/32 stranded wire.

author: joeqsmith
author_rank: Super Contributor
timestamp: September 17, 2016, 09:43:16 pm
content: Quote from: David Hess on September 17, 2016, 09:23:10 pmI think I have some small gauge wire. May be fun to try and capture it with the camera.

author: raptor1956
author_rank: Frequent Contributor
timestamp: September 18, 2016, 12:22:37 am
content: Quote from: Fungus on September 17, 2016, 09:33:07 amNot surprised they did that story.Yeah, without a pressure vessel to contain the pressure and focus it to push the bullet there isn't going to be much energy imparted to the bullet so it would require a very lucky or unlucky hit to be more than an annoyance. Still a good story though and one we in the USA can call our own...Brian

author: Cerebus
author_rank: Super Contributor
timestamp: September 18, 2016, 12:36:49 am
content: Quote from: David Hess on September 17, 2016, 09:23:10 pmThey are only so expensive because they have such restricted use, basically multimeters, so there's no competitive pressure that pushes the price down. Similar rated fuses that are more widely used are less expensive. A 14mm x 38mm 10A 500V 100kA breaking capacity industrial HRC fuse comes in at around £0.60 - 0.70 GBP compared to the £6 or £7 that I usually see the Fluke fitting fuses come in at.

author: David Hess
author_rank: Super Contributor
timestamp: September 18, 2016, 07:32:33 am
content: Quote from: Cerebus on September 18, 2016, 12:36:49 amThe fuses they use in multimeters are rated to an even higher voltage though. I agree that some of the cost is do to low demand from a specialized application but I wonder if certification figures into it as well.As far as construction, they use a granular filler which is not just sand. I forgot the contents but under conditions where an arc forms, outgassing raises the breakdown voltage and displaces the arc while melted material covers the electrode ends.

author: Cerebus
author_rank: Super Contributor
timestamp: September 18, 2016, 06:54:18 pm
content: Quote from: David Hess on September 18, 2016, 07:32:33 amDepends on the meter, my Fluke 25 is 600V, not a significant difference. I just picked a roughly similar fuse that I had a price for and that wasn't too humongous to consider similar to a multimeter fuse. Note the breaking capacity - 100 kA - Fluke specifies 10kA or 20kA depending on the meter.QuoteI think it's zeolite, a fascinating mineral that finds uses in things from washing powder to oxygen concentrators.

author: wraper
author_rank: Unknown
timestamp: September 18, 2016, 07:26:55 pm
content: Quote from: Cerebus on September 18, 2016, 06:54:18 pmFluke fuses are also 1000V rated, includingDC, not 500VAConly (with 2x lower DC voltage spec if you are lucky). 100kA at 500V has worse breaking capacity than 20kA at 1000V. Also multimeter fuses are ultrafast with very narrow carry vs breaking current range. They are not equal with usual fuses. They are made to protect the device against failure too, not only protect against fire when failure already ocured.

author: joeqsmith
author_rank: Super Contributor
timestamp: September 18, 2016, 08:47:48 pm
content: 38, 30 and 24AWG... I'm not an expert in the art of fuse repair but attempted both the straight and spiral wound techniques.

author: Performa01
author_rank: Super Contributor
timestamp: September 18, 2016, 09:22:11 pm
content: Quote from: joeqsmith on September 18, 2016, 08:47:48 pmNice video!Just … you forgot to test some rounds!

author: Cerebus
author_rank: Super Contributor
timestamp: September 18, 2016, 10:08:04 pm
content: Quote from: wraper on September 18, 2016, 07:26:55 pmThe point is economic, not technical. Don't get hung up on one specific example I plucked out of the pile - it isn't and wasn't meant to be a direct replacement just an example of how inexpensivecommonHRC fuses can be. The "not a direct replacement" part is important because the exact specs for the Fluke fuses don't intersect neatly with common fuses or there wouldn't be an explanation for why they are so damn'd expensive.There are plenty of fuses that have just as rigorous, or more rigorous, technical requirements that are relatively cheap because they are widely used and widely manufactured. As far as I can tell only Bussman, Littelfuse and possibly Siba* make fuses to fit the commonest Fluke specifications (the 11A and 440mA fuses used in the majority of their meters). [*Siba used to have a fuse that met the Fluke specs but I think they've stopped making it.]On a different note, the fusesarepurely a safety feature. It's a common misunderstanding that these fuses will protect the electronics of the meter - they won't. The electronics are protected by the usual protection devices of diodes, high impedances, PTCs, varistors etc. If you don't believe me, check out Dave's video where he dissects the protection circuitry of a Fluke meter.These are not particularly fast fuses - looking at the datasheet for the 11A fuse, break time at 20A is 250s, at 100A it's 150ms and the datasheet runs out at 200A where the breaking time is 10ms. That's about the same time-current curve as a humble 10A F m205 fuse - I'd not call that an ultrafast fuse. All of those figures represent magic smoke release for any little bit of silicon that gets in their way which is why a fuse alone isn't adequate protection for the electronics.Basically there's nothing exceptional about these fuses. The voltage ratings, breaking, I^2t characteristics and physical size are all common enough, just not in the exact combination that Fluke uses.

author: wraper
author_rank: Unknown
timestamp: September 19, 2016, 07:10:01 pm
content: Quote from: Cerebus on September 18, 2016, 10:08:04 pmSame fuses are used by other decent brands, like keysight. Price is not a tad cheaper, actually Fluke branded fuses seem to be the cheapest you can get.QuoteCompletely adequate to protect current shunt without any damage. Also check 440 mA fuse.Also other 1KV fuses with not 11A/440mA "multimeter ratings" cost the same.http://www.tme.eu/en/katalog/#cleanParameters=1&searchClick=1&search=5019906compare apples to apples.

author: joeqsmith
author_rank: Super Contributor
timestamp: September 20, 2016, 11:23:21 pm
content: Quote from: Performa01 on September 18, 2016, 09:22:11 pmHere you go. The Complete Idiots Guide to HRC Fuse Replacement.With an expansion of 67,000, we can make our own rounds! See what an inch of 30 AWG copper wire will do!

author: whitevamp
author_rank: Regular Contributor
timestamp: September 20, 2016, 11:49:45 pm
content: there she blows!!nice vid as alway joe

author: crispy_tofu
author_rank: Super Contributor
timestamp: September 21, 2016, 12:30:09 am
content: Reminds me of this:

author: whitevamp
author_rank: Regular Contributor
timestamp: September 21, 2016, 12:33:52 am
content: Quote from: crispy_tofu on September 21, 2016, 12:30:09 amnice one

author: Muxr
author_rank: Super Contributor
timestamp: September 21, 2016, 03:13:03 am
content: Quote from: joeqsmith on September 20, 2016, 11:23:21 pmWow that fuse cork rocket! That was much more powerful than I thought it was going to be. Hey Joe if you don't mind me asking, which VFD screen did you use on your pulse generator? I like the way it looks.

author: Performa01
author_rank: Super Contributor
timestamp: September 21, 2016, 09:05:32 am
content: Quote from: joeqsmith on September 20, 2016, 11:23:21 pmThat wasn't a round, it's a mortar!... and the humble, beaten up UNI-T PCB got shot in the endThanks for a both educational and entertaining video!

author: joeqsmith
author_rank: Super Contributor
timestamp: September 21, 2016, 12:09:18 pm
content: Quote from: Muxr on September 21, 2016, 03:13:03 amHere's a link to the VFD I used:http://www.digikey.com/product-detail/en/noritake-company-inc/CU20045-UW5J/286-1064-ND/1628376

author: joeqsmith
author_rank: Super Contributor
timestamp: September 21, 2016, 12:29:13 pm
content: Quote from: Performa01 on September 21, 2016, 09:05:32 amI doubt 5KY ever expected this UT61E to get so badly abused!Who knows, maybe it saved a few idiots lives.Notice how the UNI-T flexed in that frame by frame. It would have been interesting to chuck the board into a vice, measure the deflection and where it was hit, then check that with a force gauge.The problem with some of the meters I have looked at is the main inputs will breakdown. This can have the same effect, we start the process and the traces supply all the copper we need. One reason I don't like to talk about safety as we really have no way of knowing if the case will contain the blast. These reviews where the person doing the review looks at a meter and says they think it's safe, IMO is bunch of BS. Some of the meters I have ran, it's pretty obvious that their cases are not designed to handle it. And then we have some idiot who does this to a fuse. I wonder if the manufactures even think about this level of stupidity. There is nothing in the IEC safety standards about using a custom wire wound fuse as part of the test.