M4 fusible resistors wattage

Komodo

Member
Hello

Left channel is currently out. Micron FR values as marked: (schematic) measured
FR401 (390 25mA) 396
FR403 (390 25mA) 362
FR405 (680 19mA) 263
FR407 ( 33 85mA) -
FR409 (4.7 230mA) 7.2

What wattage should I use for these? I'm inclined to say FR401/403 are good.
 
Use the same kind of resistors
if you use 1/4w carbon or metal oxyde resistors , they will burn and not working like a fuse like FR does .
FR are calibrated for a specific value in Amp and they well protect your channel .With ordinary resistors this protection will no more exist and in case of big problem they will burn and maybe damage the board .
There is a reason why YAMAHA (like many other Japanese manufacturer) used Fuse Resistors
 
WATTS = Amps X Amps X R
eg, 0.23 x 0.23 x 4.7 = 0.248...

All above FR's are 1/4W

FR's "always" drift high, the reading on FR405 looks suspect. Was this in circuit
or with one leg lifted? Agree FR401, FR403 OK, yeah I'd replace FR409, first check
your MM leed resistance/touch probes together, less than 1 ohms? Then subtract this
from the FR409 reading. A 20% tolerance is probably just OK, so less than 6 would be
ok?

FR's are difficult for me to sources. Mouser doesn't carry the FRM25 series anymore
and has a limited select of the Vishay CMF, others??
 
You can use Vishay Dale RN / CMF in the correct Wattage (P = I^2 x R). Those are flame proof (and thus they will not burn). Those fusibles were chosen at the time because of there flame proof specs.
 
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FR's are difficult for me to sources. Mouser doesn't carry the FRM25 series anymore
and has a limited select of the Vishay CMF, others??

Thank you for the math. Yes they are hard to source. I've found 1/2 watt and only 1w in the 4.7 value.
I do have some Microns pulled from another scrapped Yamaha receiver but am not sure what their wattage is, I'll check. 33 and 390s.

EDIT: I've found the Vishay 1/4w 4.7, but that's it.
 
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I wouldn't. RN will handle alot more heat(current) before they burn open.
OK, I've removed that one from the cart and went with your pick 4.7 Avionic. My other Yamaha resistors are all 2w so thats a bust.

When I chose values in Digikey with fusible selected there is nothing. Still in need of at least the 33 and 680.

Going to have a Newark, Mouser and maybe Digikey order going out. Suppose that won't be the last time ever. Ha.
 
What other resistors ? The other fusibles? They are all 1/4 watters.. Digikey has them all..

Sorry, I had mentioned above that I had some salvaged FRs from another Yamaha receiver, but they are 2 watt.
I really appreciate your help Avionic.
 
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