Author Topic: Resistor metal film or metal oxide?  (Read 488 times)

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Offline Jwalling

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Resistor metal film or metal oxide?
« on: July 27, 2020, 11:45:54 am »
R30 is open. It's .47 Ohms 5%
Not sure if it is metal film or metal oxide. Does it even matter?
Thanks!

Not sure of the wattage either. it's body is 15mm in length.
« Last Edit: July 27, 2020, 11:49:49 am by Jwalling »
Jay

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Offline Zero999

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Re: Resistor metal film or metal oxide?
« Reply #1 on: July 27, 2020, 05:07:30 pm »
It looks like a metal oxide resistor.

It's quite likely something else caused it to fail, in which case replacing it would only result in another dead resistor.

What does the circuit do?
 
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Offline KevinA

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Re: Resistor metal film or metal oxide?
« Reply #2 on: July 27, 2020, 05:15:36 pm »
Looks decidedly US audio amplifier; what model is it?
 

Online 2N3055

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Re: Resistor metal film or metal oxide?
« Reply #3 on: July 27, 2020, 05:44:09 pm »
That looks like current sharing resistor for those transistors in parallel..  Both metal film or metal oxide power resistor should be fine, 2-3W by the looks of it. And like Zero999 said, that happened if transistor was hogging current. I would check it too..
 
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Offline Jwalling

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Re: Resistor metal film or metal oxide?
« Reply #4 on: July 29, 2020, 10:49:31 am »
That looks like current sharing resistor for those transistors in parallel..  Both metal film or metal oxide power resistor should be fine, 2-3W by the looks of it. And like Zero999 said, that happened if transistor was hogging current. I would check it too..

Thanks. I checked all the transistors and they're all fine. This is a voltage amplifier board for a Arbiter Systems panel meter calibrator. No schematics as is usual for this type of equipment. It fails it's power on voltage mode self test. I've ordered 3 replacement 3W metal oxide resistors. If the first one blows, then I'll have to look a bit deeper into the failure...
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Online 2N3055

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Re: Resistor metal film or metal oxide?
« Reply #5 on: July 29, 2020, 11:09:04 am »
That looks like current sharing resistor for those transistors in parallel..  Both metal film or metal oxide power resistor should be fine, 2-3W by the looks of it. And like Zero999 said, that happened if transistor was hogging current. I would check it too..

Thanks. I checked all the transistors and they're all fine. This is a voltage amplifier board for a Arbiter Systems panel meter calibrator. No schematics as is usual for this type of equipment. It fails it's power on voltage mode self test. I've ordered 3 replacement 3W metal oxide resistors. If the first one blows, then I'll have to look a bit deeper into the failure...
Glad if it was any help.
Sometimes resistors can degrade from heat and than they simply oxidize to death...
So it might be OK. I'm glad you ordered all 3, I forgot to mention that, if they are current sharing, you want them to be the same tempco if nothing else, and the remaining 2 might have degraded too..  But you obviously knew that  ^-^

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Sinisa
 


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