resistance is fusible!

[Mykle James Hansen]

Hi all,

Where do today's young hip kids go to score fusible resistors?

I am doing some repairs on a ’90’s AIWA tape deck, and the circuit makes
use of tons of fusible resistors, to protect the transistors from overcurrent.
But I’m finding that Mouser & Digikey don’t stock many fusible resistors.

More specifically: they both stock some FRs that match
the ohms I need but in higher power ratings … which would be fine
in a normal circuit but I think the lower power rating is the whole point
with a fusible resistor, right? It’s supposed to melt/burn out when the
current is too high, without flames.

And they both stock lots of carbon film resistors in the right ohms
& power rating, but those make no claims about being “fusible” or
“flameproof” or “not set you on fire”.

This is my first time ever looking for fusible resistors — maybe
because this is my first time ever renovating a transistor tape deck.
So I have no idea, maybe they’re no longer made? Did someone find
out they cause cancer? Does everybody these days just use lasers instead?

I’m looking for 2 each of:
1u/.5w
1.5u/.5w
3.3u/.25w
22u/.25w
47u/.25w

Any advice appreciated!

-m-

[Alex Faveluke]

Funny, I was just looking at fusible resistors  for the first time in my life a couple days ago.  Didn't buy any, but I might.  Who can't use  a one bit PROM once in awhile.  In my case I was thinking about it for a selectable CAN termination.  

Digi-key's got some surface mountable fusible resistors..

I wouldn't ever suggest anyone surface solder an SMT part to one thruhole pad and run kynar to the other pad, but I'd certainly do it myself in a pinch.   

There's also the "surface solder a thruhole part on the bottom of the board".  If it gets too hot, just falls right off.  Never really done that on purpose but it's come in handy accidentally once or twice!

I think somewhere your ohms character turned to u in there.. unless you mean k?

Cheers, and good luck!

Alex

 

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[Tom Moxon]

Does the 1u/.5w mean one micro-ohm resistance?
Sounds like those might be more like "current-sensing" resistors
than fuses in that application, perhaps? (got schematic?)

Bourns and Stackpole both make those, though you may not find the exact
package you want, and need to adapt for an older circuit board...
https://www.seielect.com/

There are many (better) options now (resettable, one-time, fast/slow)
for different applications of circuit protection (fuses) with different
current ranges.
Check out LittelFuse, one of my go-to mfrs for circuit protection -
https://www.littelfuse.com/products/polyswitch-resettable-pptcs.aspx

It's usually all the electrolytic capacitors that need to be replaced in
older
audio gear, those have a lifetime (hours of use) rating that may have
long expired.

best, MOX