57 deg C on a carbon film resistor ?

[ashok]

A couple of resistors in one of my circuits are going up to 57 deg C ( constant temp).
They are 2 watt types. Is this an acceptable temperature ? It is about 25 deg C above ambient.
The resistors have a maximum rating of about 150deg C and I wanted to know if anyone knows the long term effects if it is run at 57 dec .
Thanks.

[SY]

Well, the resistance will certainly be different than at room temp. Noise, too. The resistors will survive, but given how cheap they are, I'd make myself happy and put some 4 or 5 watters in that position (doubled-up 2 watters, or 5 watt metal oxide).

[ashok]

Hi Sy,
I was considering that earlier but was not sure if the temperature rise was acceptable. this is just a resistor feeding a zener diode from a 300 volt supply. But I remember having problems ( not my board ) of resistors slowly degrading the pcb at the point of entry of the leads due to high temperatures. I am using glass epoxy boards - still !

yes I think I will use a 5 watter.
Thanks.