Like a MELF, but larger?

[tomizett]

Hi All,
Another dull question about identifying and sourcing parts from me today, I'm afraid.

I have a piece of equipment for repair that uses large cylindrical surface-mount resistors of the MELF style - which I need to replace.
The problem is that they are larger than any MELF-style resistor that I can find listed by manufacturers or suppliers. Although I've seen resistors of this style before, I've never (that I remember) had to replace any.

The resistors I'm looking at are 10.5mm (0.41") in length and 4mm (0.16") in diameter.

Information that I've been able to find (like https://www.resistorguide.com/resistor-sizes-and-packages/) list only MELF, MiniMELF and MicroMELF, all of which are significantly smaller than this.

So, does anyone know what the name of this package is and where in the UK I might be able to source them? Failing that, can anyone suggest good alternatives? The value, in case it matters, is 3k3.

Thanks as always,
Tom.

 

[WA6MOK]

Not sure where in UK to get them but:
https://www.vtm.co.uk/PDF/FirstOhm Melf/FirstOhm SRM.pdf
https://www.topline.tv/ChipMelf.html

Called maxi-melf

 

[Nigel Goodwin]

Are the original resistors actually faulty?, it sounds a pretty unusual occurrence.

Assuming they are faulty?, can you not replace them with normal resistors?.

 

[tomizett]

Hi WA6MOK, thanks for the info.
I was going to suggest in jest that they could be called a "Maxi-MELF"... seems like I was right. RS in this country don't have them as far as I can tell (they're our preferred distributor) - I'll need to have a good look at Farnell and then Digikey, Mouser etc.

Hi Nigel,
The original resistors have run very hot - the enamel is cracking and at least one of them has drifted out of spec. At the moment I don't know if this is due to a fault condition, but I have a suspicion that they might just be a little under-rated for the job. If that's the case then there's obviously a case for replacing them with something a little larger - on the other hand, I generally like to give the designer the benefit of the doubt that they knew what they where doing, and fit the original parts - if nothing else, it makes for a neater repair.
The irritation is that they're on a soldered-in daughterboard and I'd like to replace the overheated Rs before I solder the board back in and move on to diagnosing the reported faults - otherwise, not only do I not know if the fault is due to out-of-spec resistors, but I'll also have to remove the board again in order to replace them before the job is complete.

All in I think I may just find some larger through-hole parts if the maxi-melfs aren't readily available.
Thanks guys.

 

[Tony Stewart]

SM_5 (5W) 7.3 x 13.5 mm $1 is my suggestion.

**broken link removed**

 

[tomizett]

Thanks Tony, that looks interesting.

<edit>
Looks like our friends at RS sell something similar. That keeps the office off my back!
https://uk.rs-online.com/web/p/surface-mount-fixed-resistors/6476469/

 

[polprog]

For the future, a folk called 3roomlab has made a very handy size comparison chart:
**broken link removed**