Glass fuse with coloured rings

[Ibex]

Hello,

My first post on this forum - I hope I have placed it in the correct location.

I am attempting to repair a Sony CFM-10 radio/cassette. It has had an easy life, sitting in its box virtually unused for most of its 16 year life. But just my luck, when I actually need to use it for something important I find it no longer works properly. 

The glass fuse on the power board appears to have failed. It looks OK, but there is no power on the output side and after removing the fuse I get inconsistent resistance readings (ranging from ~300K? to >3M?, and sometimes no continuity at all). The fuse is marked on the cap as "250V T400mAL" - which if my memory is correct means I need a time delay/slow acting 0.4 Amp fuse (to protect against power surges).

But the fuse also has something I have never come across before - 4x coloured bands on the clear glass (yellow, black, brown & blue), like the colour coding on resistors (see photo attached). I have searched the web, but I cannot find anything like this fuse. I could not find anything like this with coloured rings. I did find some resistor fuses which consist of a resistor inside a glass fuse package. But this fuse just has a tightly coiled wire inside - apart from the coloured rings it appears to be just a standard slow glass fuse.

Can I safely replace this part with a standard slow acting 0.4 Amp/250V fuse? Or is this a special resistor fuse?

The service manual for the CFM-10 lists the part as just "FUSE (T0.4A 250V)" (part number 1-532-006-00), which suggests it is just a standard fuse.

Thank you.

[Cerebus]

Looks like a normal T (i.e. delay) type to me. Given that colour code would read "4025" if it was using the standard resistor colours it's quite tempting to read that as "40" x 10mA and "25" x 10Vrms.

[Tac Eht Xilef]

There's a bunch of different codes - 2 spot, 2 band, 3 band, and 4 band - that vary quite a bit from manufacturer to manufacturer. But your's seems to be the IEC standard code found in IEC 60127-1, Annex A.

Archive.org link

According to that, it's a 400mA (yellow, black, brown = 4,0,*10) T slow blow (blue) fuse, same as is stamped on the end cap

There's also, I believe, an ANSI standard colour code. AFAIK, most of the 3 & 4 band codes stick pretty closely to the resistor colour code for current ratings between 100mA & 10A, but outside that range they get weird...

[Ibex]

Thank you both for the information.

Just for testing purposes (on battery, not mains) I substituted the duff fuse with a higher rated one cannibalised from something else. The good news is that I have power again, but still no sound (radio or tape). So replacing the capacitor which was bulging slightly hasn't resolved the problem.

Looks like I'm going to have to learn a bit lot more about electronics to get this thing working again.

[Raj]

The app called 'electrodroid' has a full page on it

[didikunz]

Hi, I have a similar request: I have a microwave oven, branded Whirlpool, that hase a small (about 20mm long) glas fuse, that I tried to replace, as it seemed burned. I took a picture before, but it is not very much in focus (what I realized when it was too late). When I took it out it bursted to dust. Does anybody has an idea, what fuse that is? Thanks in advance.

[Ian.M]

Glass fuse ratings are almost invariably stamped on the side of one of their end caps, so retrieve the debris and look at the end caps!

The PCB is marked  T10A, and what can be seen of the fuse in your first photo appears to be consistent with an IEC color coded 10A time delay fuse (Brown Black Orange wide_Blue) - See link in reply#2 above.

You are in Europe so that would be a 250V fuse.

N.B. Blown glass fuses  that disintegrate or have gone black, have usually experienced a 'hard' short circuit, (i.e. very high current) which in Microwave ovens often indicate a problem with the safety interlock door switches. 

I also recommend reading Samuel M. Goldwasser's "Notes on the Troubleshooting and Repair of Microwave Ovens" https://www.repairfaq.org/sam/micfaq.htm 

[CaptDon]

That blue band would be 6, not the 5 you indicated. In this case it means something totally different.

[Ian.M]

That blue band would be 6, not the 5 you indicated. In this case it means something totally different.

Whut?
No one except Cerebus (four years ago) is saying anything other than that the double-width blue end band means 'Time Delay'.  The fact that blue also codes for 6 is irrelevant.   Also there is no code (5) permitted in the fourth band position specified in IEC60127-1.

[didikunz]

Thanks @Ian.M, I will try with a 10A time delay fuse and post back my findings.

[CaptDon]

Sorry, didn't see the age of the Cerebus post.

[Cerebus]

That blue band would be 6, not the 5 you indicated. In this case it means something totally different.

Whut?
No one except Cerebus (four years ago) is saying anything other than that the double-width blue end band means 'Time Delay'.  The fact that blue also codes for 6 is irrelevant.   Also there is no code (5) permitted in the fourth band position specified in IEC60127-1.

And I didn't even say that, I said that it would be "tempting" to misread it.