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Resistor question I.D.

banjomaniac

Mar 3, 2013
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I have a Petsafe Deluxe in ground fence transmitter and what I think is a fusible resistor that is bad. It is gray in color, 3/8 inch long and I think 2.4 ohms. I'm not sure of the wattage value and tried to find a way to tell. From what I read looks like size is a way to tell so maybe someone can help. I attached a photo. Need the wattage and type and is it a fusible resistor or how to figure that out, best source to buy one, I have used mouser and digikey and a few others in the past.

Thanks, banjomaniac
 

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OLIVE2222

Oct 2, 2011
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Hi,

Hard to say if it' s a fuse resistor or not. I guess not according to his appearance and to the lack of warning sign on the PCB. Wattage should be in the 1-2 Watts range.

regards,
Olivier
 

shrtrnd

Jan 15, 2010
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I think you're right on the 2.4 ohms.
My comment is that it is highly unusual for a resistor to go bad by itself.
I would suspect you have other circuit damage (I'd be looking at that TO-92 Pkg
semiconductor tied to the resistor trace). I would think that the semiconductor
failed, allowing excessive current through the resistor, destroying it.
Good luck with the repair. If you just replace the resistor, expect it to also be destroyed.
 

banjomaniac

Mar 3, 2013
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Thanks for the help, I pulled that resistor and it is open so I ordered 2 from Radio Shack off EBay, free shipping $1.99 total. Anyways, the ones I ordered looked similar and were 1 watt. Now, when I turn this unit on, and have a 10 foot piece of wire connected for a short loop test the electronic collar beeps right next to the transmitter but get 1 foot down the wire and nothing. That resistor goes to the wire output so its like the wire isn't connected. I don't know, maybe I'll get lucky and won't have to spend $150 on a new unit. I'll let you know when I get it back together.

Banjomaniac
 

banjomaniac

Mar 3, 2013
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I soldered in the new resistor and it is still not working like it should. I'll move on to the other parts that might be bad, I'll see if I can find a couple other parts like the semiconductor in that same path. The resistor did not blow again but if no wires are connected and it is powered on, it should alarm and the loop light should go out, it doesn't, or I should say it randomly goes out and beeps but not like it should.

banjomaniac
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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Did you measure the resistance of the resistor you removed?
 

banjomaniac

Mar 3, 2013
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That resistor was bad, I checked it again and it was open. I was just trying to figure out that T0-92 pkg. It is stamped P0720EB and below that 4E101.

Thanks banjomaniac
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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That resistor was bad, I checked it again and it was open.

Too bad :(

I was just trying to figure out that T0-92 pkg. It is stamped P0720EB and below that 4E101.

Sounds like a sidac, see here.

It should only have 2 leads (or possibly a very short centre lead)

These are protection devices. This one is rated to break over at 100V
 

banjomaniac

Mar 3, 2013
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any way to test that part with a multimeter? I don't have a scope, and probably couldn't remember how to use one anyways, it's been about 30 years since I used one.

Thanks for the help, banjomaniac
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Just make sure it's not a short circuit.

I can't imagine its breakover characteristics are used in regular operation (but I can't be sure either)
 

banjomaniac

Mar 3, 2013
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Are you saying that T0-92 PKG should not be a direct short? I tried to figure out how to test it, looks like it acts kinda like a fuse but not sure? I tested it with ohm meter and it acts like a short so I pulled it and got the same?

banjomaniac
 

banjomaniac

Mar 3, 2013
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Part ID and testing

Here is a pic of that part, any idea how to test this? P0720EB 4E101

Thanks, banjomaniac
 

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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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If it measures as a short circuit then it has failed, and its failure probably explains the failure of the resistor.

I gave a link to a replacement part earlier. Without the circuit I can't tell if this is protective or has some other function so I can't recommend that you ret running the equipment with this removed.
 

banjomaniac

Mar 3, 2013
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OK, I soldered in the new parts from digikey and everything is working now. Thanks for all the help. I have a ground and surge protector made for the invisible fence so I'll use that and hopefully no more problems.

banjomaniac
 
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