Identification of fusible resistor A53K 15 ohm / 130°C - Page 1
Forum section: electronics / repair

author: Greybeard
author_rank: Frequent Contributor
timestamp: December 10, 2021, 01:19:54 pm
content: I need replacement of a fusible resistor 15 ohm / 130°C (A53K type ?).Where can I order these?

author: ESTechnical
author_rank: Contributor
timestamp: December 10, 2021, 01:44:22 pm
content: I found a datasheet for several similar resistor + thermal fuse in a ceramic case, they all seem to be end-of-life.I can't find these exact items, but I did find this page where they seem to specify the types of fusible resistor you are looking for.https://www.akaneohm.com/products-data-eng/rwt05a/but I don't think this is a lot of help, assuming you just want a single replacement item.There is a different style from schott, called sefuse. These seem to be readily available. Perhaps you could combine the right temperature characteristic with a resistor of the right rating and resistance. The "sefuse" parts are on ebay and other large component suppliers. For examplehttps://www.ebay.co.uk/itm/173884281548

author: Greybeard
author_rank: Frequent Contributor
timestamp: December 10, 2021, 02:37:54 pm
content: Yes, I need one or two of these.I found an ebay offer from UK seller but wrong resistance and high shipping costs to Germany (couldn't find an el-cheapo chinese seller on ebay).I'm thinking about using a standard 5W ceramic resistor instead, but I don't want to risk a fire if something goes wrong.This fusible resistor is used in a SMPS between mains rectifier and 400V/330uF electrolytic cap.There is a 3A glass fuse between IEC mains terminals and input filter, too.

author: ESTechnical
author_rank: Contributor
timestamp: December 10, 2021, 02:54:16 pm
content: I'd try and keep the function as close as possible for a similar degree of fire protection. A suitable rating 15R resistor strapped to one of those thermal fuses would seem the safest thing to use. Perhaps glue them together with permanent heatsink bonding compound? It seems to serve as inrush protection plus overload protection. The datasheet for the part I found earlier implied the ceramic ones contain a thermal fuse in series with a resistor, thermally coupled.

author: gamalot
author_rank: Super Contributor
timestamp: December 10, 2021, 03:01:40 pm
content: I found Micron 5EG series 15 ohm / 135°C thermal fused power resistor on Aliexpress, but the price is so high! ($15/5pcs)https://www.aliexpress.com/item/4001355668809.html

author: Greybeard
author_rank: Frequent Contributor
timestamp: December 10, 2021, 03:28:17 pm
content: Quote from: ESTechnical on December 10, 2021, 02:54:16 pmIt seems to match the original very well, but nobody sells these for a reasonable price...So maybe the DIY combo will do.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: December 10, 2021, 08:24:40 pm
content: Quote from: Greybeard on December 10, 2021, 03:28:17 pmI found one of these recently in a Roland powered mixer SMPS, only it was 5.1 ohms, 130oCAnd yes, there was a standard mains input fuse before it.I broke it open, and the construction was identical to that diagram, the fuse was open, the resistor undamaged.There was no fault with the unit, just this fuse had died.I have to question why it is there in the first place.Most other SMPS based equipment I've ever seen doesn't use such a device.

author: Greybeard
author_rank: Frequent Contributor
timestamp: December 11, 2021, 10:04:33 am
content: Quote from: Audiorepair on December 10, 2021, 08:24:40 pmIt's the way it should fail, if the temperature in the device/component gets too high (fire protection).Quote from: Audiorepair on December 10, 2021, 08:24:40 pmThat's exactly my experience, too.I've just found some hints referring to some SONY SMPS.My SMPS is labeled by Yokogawa. Probably this unit is designed for better fire protection than cheapest chinese units.

author: Greybeard
author_rank: Frequent Contributor
timestamp: December 11, 2021, 10:24:30 am
content: I've opened the case of my unit using a small chisel to spilt the top of the ceramic bin off, to expose the junction between resistor and temperature fuse.It turned out the fuse is OK and the resistor is open.So the failure is not caused by over-temp but by component failure of the resitor (broken wire or joint).I think, I will disassemble the unit to re-use the thermal fuse in combination with a standard 5W resistor.

author: sleemanj
author_rank: Super Contributor
timestamp: December 11, 2021, 10:51:57 am
content: Seems to me like it would be acting more like a really really slow blowing fuse than acting on external heat being as it's a fuse so tightly coupled to a resistor, and all surrounded by ceramic to keep the outside environment away and the heat in.I guess it's acting for inrush current limiting to the big cap to handle if the cap goes bad and has a high ripple which would cause that resistor to heat up more and blow the fuse. Just a guess.I think if it was me I'd just replace with a 5R 5W cement resistor, and a thermal fuse strapped to it maybe (well, to be truthful I'd probably not bother with the thermal fuse because I have lots of cement resistors but no thermal fuses in my junk pile).

author: Greybeard
author_rank: Frequent Contributor
timestamp: December 11, 2021, 11:05:56 am
content: After disassemby I found the resistor wire blown by pulse overload or material defect.QuoteI will do that.I'm just searching the 15 ohms 5W resistor in my parts pile...That's my typical standard repair:1: finding the failure - 10 minutes2: finding specs of the component - 1 hour3: finding vendor of the component - 2 hours seaching -> not found4: thinking about an alternative way to fix - 1 hour5: searching the junk pile for component - 2 hoursI'm happy to do all that for fun, not for money...