In-rush resistor failed

Hi All,

I just thought I'd say this LG DVD/VCR unit discussed below is still working fine with the new in-rush resistor installed.

Ross

Hi All,

A friend of mine has an LG DVD/VCR combination unit which suddenly went completely dead.

These units are getting pretty hard to buy these days, so I lent her an old VCR of mine so she could use her VHS tapes.

It seemed to me it was likely a power supply problem, and so it proved to be.

A 2.2ohm 2W current in-rush resistor right at the mains input had gone open circuit. I went down to Jaycar and bought a 5W resistor for $0.40 and once I installed the new resistor the unit sprang into life again.

Checking voltages around the power supply then the voltages are generally what I would expect to find. Nothing looks damaged or overheated anywhere. No bulging capacitors either.

However, it has been my experience that repairing these switching power supplies is never quite as straightforward as it might seem to be in the first instance. Most of the components are fairly highly stressed and one weak sister can fail other components and the weak sister survives itself.

Anyway, while I guess the inrush resistor might fail open like any resistor might rarely fail this way, is there anything else I ought feel suspicious about if this in-rush resistor fails?

And just by the way I don't really understand why this resistor needs to be 2W either. VCR's usually only use about 5-10 watts or so, so it is hard to see where 2 watts of heat comes from in the 2.2 ohm resistor. Or is this resistor really being sized for a voltage rating and the 2W rating just comes with the voltage rating territory?

Ross

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