Rare fuse annoyance!! - Page 1
Forum section: electronics / general

author: unknownparticle
author_rank: Frequent Contributor
timestamp: December 03, 2022, 09:13:09 pm
content: Just started a check over on a Farnell bench PSU I bought sometime ago, quite retro, probably a 70's unit. Fair condition but functionally unknown, until this afternoon. Long story short, the DC output fuse has popped. Shouldn't have been a problem, ha!Removed the fuse from the screw in holder on the rear panel, expecting the usual 20mm glass cartridge type, or possibly a 32mm. No such luck, it's a 16mm, or 5/8"!!!! I have never seen that size fuse in any UK test gear until now and it's proving tricky to find. Some of the bigger component operators do list it but so far it's either 5 at £1.89 each, or 1 at £7.89!!! Plus shipping of course!! There are some on feepay, but all in the US!! What a pain!

author: Gyro
author_rank: Super Contributor
timestamp: December 03, 2022, 09:16:08 pm
content: It would be simpler just to replace the fuseholder if it's panel mount.

author: themadhippy
author_rank: Super Contributor
timestamp: December 03, 2022, 09:28:50 pm
content: Quoteget a 32mm,double the wanted value and cut it in half

author: jonpaul
author_rank: Super Contributor
timestamp: December 04, 2022, 02:08:46 pm
content: common US little fuse type, ask on a ham radio site or flea, BVWS is in UKJon

author: unknownparticle
author_rank: Frequent Contributor
timestamp: December 04, 2022, 04:51:17 pm
content: Quote from: themadhippy on December 03, 2022, 09:28:50 pmQuote from: Gyro on December 03, 2022, 09:16:08 pmIt's nasty to access and I'd prefer to keep it original.

author: Stray Electron
author_rank: Super Contributor
timestamp: December 04, 2022, 05:21:48 pm
content: Is the fuse in an externally fed power circuit or the circuit being tested? Can you short out that internal fuse and use an external inline holder for a common size fuse instead?

author: TimFox
author_rank: Super Contributor
timestamp: December 04, 2022, 06:42:56 pm
content: Is the fuse a 2AG, as found in the Littelfuse catalog?Nominal 5 x 15 mm, available either as cartridge or with leads.https://www.littelfuse.com/products/fuses/cartridge-fuses/2ag-5x15mm-fuses.aspx

author: unknownparticle
author_rank: Frequent Contributor
timestamp: December 05, 2022, 03:25:35 pm
content: Quote from: Stray Electron on December 04, 2022, 05:21:48 pmCould do but then every time a fuse blew I would have to take off the top cover of the case, that's 6 screws!! Not the end of the world but hassle I would prefer to avoid.Quote from: TimFox on December 04, 2022, 06:42:56 pmThanks, I know the fuse is easily available in the US, several ebay US sellers list them, but the cost is prohibitive to the UK.Seems that I will have to order from one of the big UK parts sellers, like Farnell and bite the price bullet!! Still wondering why Farnell used this size in this PSU, I have many Farnell PSU's from the past 40 years, and none of them use this sized fuse, they are all 20mm or 32mm. The mains fuse is the same so I'll need to order some for that also! I'll bet thats why this unit was taken out of use, they couldn't find a fuse!

author: TimFox
author_rank: Super Contributor
timestamp: December 05, 2022, 04:53:16 pm
content: A quick look at Mouser UK has Littelfuse 2AG fuses for roughly 1 GBP in single quantity.

author: AVGresponding
author_rank: Super Contributor
timestamp: December 05, 2022, 04:56:28 pm
content: Rapid has them for between £1.69 and £4.67 for a pack of 10https://www.rapidonline.com/eska-515-663-quick-acting-5-x-15mm-glass-micro-fuse-3a-250v-pack-of-10-54-4433Is Dave fiddling with the forum settings again? Had to futz with that link to get it to work

author: tom66
author_rank: Super Contributor
timestamp: December 05, 2022, 05:07:47 pm
content: Did Farnell ever design their own kit? I thought most if not all of it was rebadged, and therefore this particular PSU probably came from a far eastern manufacturer, or if you were lucky, some weirdo American or European supplier that used a strange fuse because they could get them on bulk order for a cent apiece.

author: AVGresponding
author_rank: Super Contributor
timestamp: December 05, 2022, 05:18:27 pm
content: I asked that question myself once, and was told by someone who knows what they are talking about that yes, they did. Unlikely that they still do I'd guess, given the economics of the stuff from China.

author: TimFox
author_rank: Super Contributor
timestamp: December 05, 2022, 05:29:15 pm
content: Since when is 5 x 15 mm a strange size to people outside of North America?LittelfuseTMis an old-line fuse manufacturer in US, although like everyone else they shifted production to China, and supply 2AG fuses.Their mechanical spec is (4.2 to 4.5 mm) diameter and (14.1 to 14.9 mm) overall length.Another manufacturer I found for 2AB is Ferraz Shawmut, now renamed Merson, who make "SMB" and "STG" nominal 4.5 x 14.5 mm glass fuses.

author: unknownparticle
author_rank: Frequent Contributor
timestamp: December 05, 2022, 05:49:15 pm
content: Quote from: TimFox on December 05, 2022, 04:53:16 pmI hadn't checked Mouser as I never use them normally, but they do indeed stock the 1 amp and 100 ma values I need at reasonable prices, so many thanks for thatQuote from: AVGresponding on December 05, 2022, 04:56:28 pmThanks but they don't hold the values I need.Quote from: tom66 on December 05, 2022, 05:07:47 pmThey most certainly did! I used to live near their factory, up until the early 80's and visited a number of times so saw their production lines, it was a big operation. The construction of Farnell products is very obviously British of the period, and up until the mid 80's was of very good quality. They started to cost cut from then until they stopped manufacturing in the 90's though, the later stuff was ok but not upto what it had been. The 70's in particular was excellent, proper chassis's, hand laced harnesses etc. The one I'm working on is a 70's bench PSU, 0-30 volts at 1 amp, fully linear and built like a tank. Not upto HP standards, but what else was? With their military contracts they could afford to make stuff to the ultimate standards.

author: AVGresponding
author_rank: Super Contributor
timestamp: December 05, 2022, 06:40:55 pm
content: Quote from: unknownparticle on December 05, 2022, 05:49:15 pmNo 1A but they do have the 100mA oneshttps://www.rapidonline.com/eska-515-607-quick-acting-5-x-15mm-glass-micro-fuse-100ma-250v-pack-of-10-54-4418

author: factory
author_rank: Super Contributor
timestamp: December 05, 2022, 06:55:03 pm
content: Quote from: unknownparticle on December 03, 2022, 09:13:09 pmSounds like the fuse is a Belling Lee size 00, I've seen these tiny fuses in Farnell, Racal and some other 1960's test gear. They also made the fuse holders for 20mm fuses and it's not obvious until you unscrew the cap.Quote from: AVGresponding on December 05, 2022, 04:56:28 pmMust have been, as the file upload now has a drag & drop feature, not tried it though.David

author: tooki
author_rank: Super Contributor
timestamp: December 10, 2022, 11:08:09 am
content: Quote from: tom66 on December 05, 2022, 05:07:47 pmYes, they did. Not just designed, but also manufactured, in the UK via a subsidiary called Farnell Instruments. And in fact, a sort of descendant company still exists:https://advanceproductservices.co.uk/about-us/our-history/I discovered this recently when an old Farnell Instruments bench power supply came into the lab to have RIFA vomit cleaned and said cap replaced, and curiosity got the best of me (again). :p

author: G7PSK
author_rank: Super Contributor
timestamp: December 10, 2022, 02:48:30 pm
content: In the past I have removed the end cap of glass fuses and soldered a new piece of fuse wire in.

author: eti
author_rank: Super Contributor
timestamp: December 11, 2022, 05:16:26 am
content: Sounds... con-fusing