Questions for Fusible Resistors

[cbr600rr_blue]

Hope that experts can share their views here

I have a blown fusible resistor labeled as W1/2J 2.2 ohm FU985. I interpreted it as 0.5 Watt, +/-5% tolerance. I can't read out further information. The dimension of this blown fusible resistor is 10mm in length and 5mm in diameter as the attached photo. It is relatively big.

When I tried to order this online, tyco FRN50 seems to have same specification. But the dimension of FRN50 is much smaller.

It is 6.3mm in length 2.3mm in diameter.

It is only about half of the size of the blown one. Will this replacement work?

I have attached the specification for FRN50. Does size matter especially the heat and thermal concerns?

[cbr600rr_blue]

Re: Questions for Fusible Resistors

Hi,
no one can share the knowledge?

[budm]

Re: Questions for Fusible Resistors

If you look at the spec, the withstand voltage after fusing (after blown open) is one of the important number to compare to the old one. It is similar to the fuse voltage rating, I.E. you do want to 5A 32V car fuse to replace the 5A 250V fuse used in the line operate equipment.
Do you know where this fusible resistor is used in the circuit and how high is the voltage it is being used in?

[Longbow]

Re: Questions for Fusible Resistors

Application? A fusible resistor is not a fuse, it is a resistor that is usually made of fireproof material, and designed to smoke at a certain current level. The wattage of the resistor will determine if the resistor smokes or just gets warm. Even if you can't find a reference for those numbers, look at your circuit to see what is required.

[budm]

Re: Questions for Fusible Resistors

There is FLAME PROOF resistor, and then there is FUSIBLE resistor/FLAMEPROOF fusible resistor that serves 3 functions.


http://www.interfacebus.com/Electron...r-terms-F.html

When it goes open, it must not allow the voltage to jump over the open circuit, thus the the withstand voltage after fusing rating is provided.
FRN series is the Flame proof Fusible resistor.

EMC and ULW are aimed chiefly at mains input protection for
small power supplies and battery chargers. Here it performs
three circuit protection functions:

1. Providing protection against supply line voltage transients,
often in conjunction with a shunt element such as a Varistor
or Transient Voltage Suppressor (TVS). This enables the
designer to achieve the required level of immunity to
conducted lightning induced surges.

2. Restricting the peak inrush current at switch-on to levels
suitable for the rectifier bridge and consistent with good
EMC design.

3. Preventing fire by fusing safely under fault conditions such
as rectifier or capacitor breakdown.

[cbr600rr_blue]

Re: Questions for Fusible Resistors

Hi,
This is for Sharp AQUOS LCD TV power supply board DPS-226-AP-1. It's at primary circuit so it must be 230volts AC.

So can this replacement fusible resistor FRN50 be used but with a much smaller dimension?

[redwire]

Re: Questions for Fusible Resistors

Size of a resistor and it's temperature rating determine the wattage. That resistor is the size of a 2W part.
I would not use the 1/2 part as a replacement.
Most power resistors are rated at 70°C, so their size determines the wattage.

Yageo Flame-Proof type_RSF.pdf

[cbr600rr_blue]

Re: Questions for Fusible Resistors

Hi
I thought that W1/2J is 1/2Watt (0.5Watt) because J is tolerance.

If you look at the spec, the withstand voltage after fusing (after blown open) is one of the important number to compare to the old one. It is similar to the fuse voltage rating, I.E. you do want to 5A 32V car fuse to replace the 5A 250V fuse used in the line operate equipment.
Do you know where this fusible resistor is used in the circuit and how high is the voltage it is being used in?

[cbr600rr_blue]

Re: Questions for Fusible Resistors

This is the photo for the blown fuse before desoldered.

If you look at the spec, the withstand voltage after fusing (after blown open) is one of the important number to compare to the old one. It is similar to the fuse voltage rating, I.E. you do want to 5A 32V car fuse to replace the 5A 250V fuse used in the line operate equipment.
Do you know where this fusible resistor is used in the circuit and how high is the voltage it is being used in?

[budm]

Re: Questions for Fusible Resistors

More likely to be for main B+ line which will be around 330VDC. Trace out the circuit to see if one end is connected to the + terminal of the main filter cap (450VDC rating). There must be shorted out components that you need to checked out.

[cbr600rr_blue]

Re: Questions for Fusible Resistors

Hi,
Actually this is related to another post few days ago where a TNY264PN IC crack. At that time, U only replace the IC but didn't know that this fusible resistor also blown.
see the link:
https://www.badcaps.net/forum/showth...264#post436087

More likely to be for main B+ line which will be around 330VDC. Trace out the circuit to see if one end is connected to the + terminal of the main filter cap (450VDC rating). There must be shorted out components that you need to checked out.

[budm]

Re: Questions for Fusible Resistors

So it is the fusible resistor for feeding the B+ which is around 330VDC. So the fusing withstand voltage should b e more than 330v

[redwire]

Re: Questions for Fusible Resistors

Looks like it is made by Futaba. They have some funny names for their resistors: "ANTI-BURST FUSIBLE RESISTOR", "HEAT ENERGY SURGE WIRE WOUND FUSIBLE RESISTOR" etc. Take a look under "fusible" category.
Note a fusible resistor has two voltage ratings - the max. working voltage, and the max. fuse voltage. This is a 2.2R beast, so it would normally never seen more than a few volts.
Why it is so big and really a 1/2W? I guess its a high-voltage type, or non-inductive if used as a snubber.

[budm]

Re: Questions for Fusible Resistors

https://www.badcaps.net/forum/showth...264#post436087

Lets stick to one thread.

[cbr600rr_blue]

Re: Questions for Fusible Resistors

https://www.badcaps.net/forum/showth...264#post436087

Lets stick to one thread.

Hi,

Followed by the replacement of 2.2 ohm fusible resistor, the LCD TV powers up nicely now.
Thanks everyone help.

[cbr600rr_blue]

Re: Questions for Fusible Resistors

Hi,
You are great! The FU is FUTABA.
It's Taiwanese maker.
It's antiburst no wonder the size is bigger than usual.
Other makes are usually flame-proof only

Looks like it is made by Futaba. They have some funny names for their resistors: "ANTI-BURST FUSIBLE RESISTOR", "HEAT ENERGY SURGE WIRE WOUND FUSIBLE RESISTOR" etc. Take a look under "fusible" category.
Note a fusible resistor has two voltage ratings - the max. working voltage, and the max. fuse voltage. This is a 2.2R beast, so it would normally never seen more than a few volts.
Why it is so big and really a 1/2W? I guess its a high-voltage type, or non-inductive if used as a snubber.

[steinless]

Re: Questions for Fusible Resistors

Hey all would like to ask, if i replace it with a 4.7 ohm fusuable, would it affect anything?

[SteveNielsen]

Re: Questions for Fusible Resistors

You should always replace a fusible resistor with the same value.

[jeremykum]

Re: Questions for Fusible Resistors

Just wish to say thank you for the people sharing here.
Now trying to fix a Sharp DSP-174AP board from 40", owner claims lightning strike.

Initially located a Toshiba K3256 N channel FET shorted. Circuit not shorted. Replace it but still not powering up.

Now notice this W1/2J 2.2 ohm should be dead. This board have 2 pcs of these at the main cap 320V. The R7910 input 320V, while output only 1.5V. Will try to order and replace it.

[nickgronk]

Re: Questions for Fusible Resistors

Does anyone know of a suitable replacement for this resistor. I am having a hard time finding a good replacement.