[sdiy] Making toast with chips

[Lincoln Fong]

Can anyone tell me if Opamps should ever run hot (to the touch) and what
it implies if they are? I notice on some audio boards I'm looking at
that the NE5532s (and 5534s) are hot to the touch. Some hotter than
others. None of them is under much of an output load and the supply is a
good quality +/- 15V fed in groups through fusible 4.7 ohm resistors
that periodically blow. Each chip has a pair of 47nF ceramic PS
decoupling caps right by it though they're 12 years old now. Am I right
in thinking that the ones that are hottest to touch are the most likely
to cause excessive current draw or is it a red herring? After all the
boards don't give trouble 95% of the time- not a very good average I
know. The odd thing is that usually replacing the resistor cures it at
least for a while.

I notice the hotter ones generally (though not exclusively) have a P
suffix and are dual types while the cool ones are N suffix.

Finally do some of you use some kind of (infrared?) thermometer to test
ICs for symptoms of trouble? I would get one if this were the case. What
would be a 'dangerous' temperature?

Lincoln 
_________________________
Lincoln Fong
http://www.fongelectronic.com