Want to replace resistors myself, but need an advice

weiyann83 over 1 year ago

based on documentation it show 2.2 1/2W J, not sure which resistor i need to replace? any expert can guide me?

Thanks

elektrotanya.com/.../download.html

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anniel747 over 1 year ago +1

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0 weiyann83 over 1 year ago

The original resistor appears as shown, and I have observed that it consistently burns R7914 and cracks IC7905. Additionally, I have replaced the 3x power boards over the past four years.

rio
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0 JWx over 1 year ago in reply to weiyann83

If the IC cracks and resistor burns I would suspect IC failure (mosfet stuck in conducting state, leading to overheating and burning of the resistor). Maybe some overvoltage spikes? If it was the same board I would also suspect some other component failure that is killing converters - but as I understand power modules were replaced?
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0 robogary over 1 year ago in reply to weiyann83

The resistor is likely the victim of another problem. This is the IC7905 spec.

https://www.mouser.com/datasheet/2/328/tny263_268-1512708.pdf

JWx has good ideas. Maybe it needs troubleshooting with a scope to see spikes or maybe one of the surrounding diodes has failed open.
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0 anniel747 over 1 year ago

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0 weiyann83 over 1 year ago in reply to anniel747

Is not common I don’t see element14 got sell this type of resistor, if you can provide link which type of fusible resistor very much appreciate.
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0 weiyann83 over 1 year ago in reply to robogary

Ic i able to find from element14, but fusible resistor same spec i cant find from the element14 any alternative resistor fusible we can use?
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0 anniel747 over 1 year ago in reply to weiyann83

canada.newark.com/.../97K6497
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0 acdc90 over 1 year ago in reply to weiyann83

please check on the secondary of the transformer for shorts across diodes etc

it sounds like each board is less than a year old ( so not warranty)
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0 phoenixcomm over 1 year ago in reply to weiyann83

weiyann83 could be that as JWx suggested the MOSFET is stuck ON. One thing you could do (a little nuts) 2.2Ω 5W 5% fusible resistor. and mount it off the board maybe even bend a small aluminum into a U-shape and clamp it to the resistor. personly you could use a hose clamp BYW heat compound is used as well. You realize that this is OVERKILL ~~ Cris
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