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it seems to be at primary side but you should give us some more info to try helping you. Where is it connected? Do you have some schematic from the power supply? Is any name or reference at power supply?
THe Resistor is probably between AC input Bridge and Caps to reduce surge currents on start. It probably should also or be instead an Inrush Current (ICL )limiter if there is no bypass delay Relay. SUrge currents can be 10x avg for 10% ripple. Since it is a 48W supply, I would choose an ICL which has NTC value to hold whatever current is needed for 48W. Like a holding current of 210mA at 230V
Nearest > is 250mA R @ 25°C 30 Ohm Tolerance ±5% Current - Steady State Max 250mA R @ Current 4.70 Ohm
How does that compare with R value replaced several times ??
2pac Mafia sorry I do not have schematic but here Tony Stewart is explained exactly where it is and what it is. I used to replace with 47 to 51 ohms resistor but blown off frequently and damaging the board. What might be the cause? Tony Stewart I do not understand what is ICL with NTC value?
ICL was defined
NTC means neg. tempcoeff. so when it gets hot after power ON R drops to reduce heat loss and improves bridge voltage on cap
if it was 250mA * 50 Ohms , power dissipation PD= 1/4*1/4*50 = 3 1/8th Watt too hot but during power up current will be 8x this much. as surge current to charge up and this is steady power >3W.
If it was 30 Ohms then Pd= 1/4*1/4*30= 15/8 W or almost 2W which is ok for startup
then when hot ICL reduces to 4.7 Ohm or Pd= 0.3W (cool)
But using fixed 5 Ohms increase surge current to Bridge and Caps 10x and then they blow instead after a while. (reduced life)
So ICL is better to reduce heat and stress to caps which results in bulged lids from surge current or excess ripple current if ICL is too low in value.
Therefore the max holding current is specified for use and I read this LCD uses 48W max.
then you already have an NTC in AC line which would work as an inrush current limit but you have the resistor which is failing connected from AC line to earth, is that correct???
Assuming that 'circuit' is accurate, then it's a static discharge resistor, and should be a HIGH value - it's connecting the neutral (hopefully, but not crucially) to the chassis - to provide a discharge path for static build-up on the chassis.
If you're replacing a multi-hundreds of kilohm's resistor with a 50 ohm one it's not surprising you're having problems?.
You don't have you location filled in, which is often VERY important, such as in this case - as doing what you're doing should instantly blow the RCD (earth leakage trip) - so presumably you don't have them?.
I think the blue component in parallel with the resistor should be in this case a capacitor and the resistor as Nigel told you should have a high value
I think the blue component in parallel with the resistor should be in this case a capacitor and the resistor as Nigel told you should have a high value
Then the last schematic you shared is wrong, the resistor should be in series with NTC as Tony said for inrush current limit.
When the resistor was burnt, could you read the value or you supposed it?
Can you confirm the exact location of the resistor in the circuit?
Can you tell us the reference from the blue component connected in parallel to the resistor?
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