Electronic component query - fuse resistor ?

[robgraham]

I've got a cassette deck - still used for educational material - that has failed and it would appear that a device called a "fuse resistor" in the voltage regulator circuit has gone open circuit. It's defined as 3.3 ohms, 1/2w and the service manual indicates 1 volt across it, indicating a current of 300ma.

Although RS stock something similar, there is not an immediate replacement. Is there someone here who could advise me if I could replace it with a 3.3 ohm resistor and a 500mA fuse ? I'm hoping of course that it is just old age that has gone for it and not something further down the line.

Thanks

Rob

[Rob G]

I've been told on another forum that they are called 'Fusible Resistors'. I've now found several suppliers via Mr Google.

Rob

[meow2222]

Yes, resistor plus fuse does the same job.

NT

[Arfa Daily]

Fusible resistors often fail for no good reason, although of course, there may be be a downstream fault, which is what they are there to protect against ...

I would say on average, that I replace at least 1 or 2 fusibles a month in all sorts of audio equipment, and maybe a couple a year have failed for a 'real' reason. I wouldn't be *too* paranoid about getting exactly the right value, nor about adding a fuse as well. As long as any replacement that you fit is 'ballpark', it will still fail in short order, if a genuine fault occurs at some time in the future. That said, you shouldn't have any problem obtaining a replacement in a value of 3R3.

Arfa

[Clint Sharp]

In message , Arfa Daily writes

One of the 'features' of the fusible resistors is that they don't burst into flames when they 'fuse' so replacing one with a standard resistor and fuse could have unintended safety implications.

[Arfa Daily]

Yes, agreed. Also, I wasn't implying that a different 'type' of resistor should ever be fitted, although I can see reading my post again, that I perhaps didn't make that clear, so let's put that right now. What I was intending to mean was that any fusible resistor *value* in the right ballpark - so a 2R2 or 4R7 - would not be a problem, if a 3R3 was not readily available to the poster. Any replacement should also have a similar power rating to the one being replaced, although this is not always apparent just by looking. I have seen 1 watt fusibles that are smaller than 1/2 watt ones. This is a situation where if you want to preserve the safety ratings

*exactly* as they were, a service manual with a parts list is needed, and if that doesn't make clear what the power rating is, the replacement device would have to be ordered from the manufacturer.

Arfa