Power rating for fusible resistor - Page 1
Forum section: electronics / repair

author: giosif
author_rank: Frequent Contributor
timestamp: July 03, 2025, 04:49:08 pm
content: I am trying to determine the power rating for the fusible resistor in the attached pictures.I think I found the manufacturer and the series of resistors - Supertech Anti-Burst Fusible Resistorhttps://www.supertech.com.tw/products_detail/90.htm- but their specs sheet is a bit hard to read, plus I cannot seem to find the 17 or 1.7 or 1/7 W power rating I believe I read on the blown resistor.Any suggestions/guesses?

author: Hamelec
author_rank: Regular Contributor
timestamp: July 03, 2025, 06:17:00 pm
content: F1/2J means:Film, 1/2Watt (=0.5Watt)(1/4W has color code)

author: giosif
author_rank: Frequent Contributor
timestamp: July 03, 2025, 09:21:50 pm
content: Thank you for the clarification!Just a small amendment: based on the datasheet on the manufacturer site, I am guessing the P/N is F12J, rather than F1/2J.

author: Hamelec
author_rank: Regular Contributor
timestamp: July 04, 2025, 09:07:51 am
content: i talked about the marking of YOUR resistor - you can see also an example in the uppermost picture of the datasheet

author: giosif
author_rank: Frequent Contributor
timestamp: July 04, 2025, 04:04:18 pm
content: Quote from: Hamelec on July 04, 2025, 09:07:51 amAh, fair enough.What is interesting is that even the resistor I took pictures of most likely has F1/2J written on it; however, the datasheet suggests it should be F12J.

author: tooki
author_rank: Super Contributor
timestamp: July 04, 2025, 04:42:03 pm
content: Quote from: giosif on July 04, 2025, 04:04:18 pmProbably because the datasheet is likely not for what you actually have; they don’t look the same (the construction is very obviously different), the resistor you have has a logo on it, etc.I’m sure there are tons of companies making them, and using similar, but not necessarily identical, markings.Edit: I’m pretty sure what you have is this:http://www.futaba.com.tw/categories/category_view_en/140The logo on your resistor sure does look like a simplified version of theirs.PDF datasheet attached.

author: giosif
author_rank: Frequent Contributor
timestamp: July 04, 2025, 04:47:04 pm
content: Quote from: tooki on July 04, 2025, 04:42:03 pmI am aware the photos in the data sheet look different from my resistor, but I thought the brand is the same (isn't that "FU" type of marking a logo?) and, within their set of products, this type of resistor is the only one matching the purpose and resistance value of my resistor.

author: tooki
author_rank: Super Contributor
timestamp: July 04, 2025, 04:49:33 pm
content: Quote from: giosif on July 04, 2025, 04:47:04 pmSee the edit I just made to my reply.

author: tooki
author_rank: Super Contributor
timestamp: July 04, 2025, 04:52:52 pm
content: Quote from: giosif on July 04, 2025, 04:47:04 pmIt is. But where do you see that logo on the datasheet you linked? That company’s logo looks nothing like that.But the fact that the resistors aren’t even the same shape should have been a watertight clue that it’s not the same product.Quote from: giosif on July 04, 2025, 04:47:04 pmWithin whose set of products? The closest you could find within the wrong manufacturer doesn’t really tell you much.

author: giosif
author_rank: Frequent Contributor
timestamp: July 04, 2025, 07:11:05 pm
content: Quote from: tooki on July 04, 2025, 04:52:52 pmLook at second resistor from the bottom in the photo on the page a linked in my initial message - you will see the exact logo as on my resistor.That said, "FU" is strange for a company called Supertech, which leads me to the next comment below.Quote from: tooki on July 04, 2025, 04:42:03 pmThis is most likely the manufacturer.Thank you for finding it!What is interesting is their datasheet and the one from Supertech have the exact format/style.Quote from: tooki on July 04, 2025, 04:52:52 pmGenerally, yes, but my thinking was the manufacturer might change the appearance of the product - e.g. if they change their manufacturing process or source materials - but still consider it the same product.Quote from: tooki on July 04, 2025, 04:52:52 pm"their set of products" = the manufacturer'sWhat I meant was, if you look at the range of products my initial manufacturer makes, the "Anti-Burst Fusible Resistor" category is the only one closest to the type of resistor I have.In any case, we now know the actual manufacturer is very likely Futaba, as per your finding.

author: Gyro
author_rank: Super Contributor
timestamp: July 04, 2025, 07:31:13 pm
content: It's unusual to see a fusible resistor eject material like that, they usually look reasonably normal and get picked up by a continuity test. Not quite the 'anti-burst' they're made out to be.If it has failed violently, it probably points to a short very close downstream (assuming that this is the Delta SMPS). Maybe the bridge rectifier.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: July 05, 2025, 02:24:40 pm
content: Quote from: giosif on July 03, 2025, 09:21:50 pmThere is too much room in between the "1" and the "2", and near the bottom you can also see a part of the slash. I guessed there was a slash written on the resistor before I read the comment from Hamelec. 1/2Watt also matches with the resistor size, while 1/7Watt would be very low for a THT resistor, and also a non standard value. Maybe you're looking at a datasheet from a different manufacturer?(I did not read the whole thread).

author: giosif
author_rank: Frequent Contributor
timestamp: July 05, 2025, 07:05:03 pm
content: Quote from: Gyro on July 04, 2025, 07:31:13 pmYes, it is from the Delta SMPS and, yes, the bridge rectifier is shorted.I too think this must have been some spectacular failure of the PSU.Quote from: Doctorandus_P on July 05, 2025, 02:24:40 pmAgree. It's just that the data sheet I was looking at originally showed no version with "1/2" marking (it talked about a "12" marking for 0.5W).And, yes, I was using the wrong data sheet.