Crumar Musical Instruments User Group.

> Lower making warbly noises coming from voice 1 circuit TL072ACP which
> is incidentally about 500 degrees and burned the dickens out of my
> finger. When cooled with compressed air or freeze spray, it quiets
> down, No Noise generator audible
> 
> Any idea why this component would be running so hot?

Because it's died.  Several of possible reasons.

1.  Check the supply.  For a TL072 you should have -12v on pin 4
    and +12v on pin 8 (NOT pin 7).  

2.  Has it been accidentally been put in wrong way around during
    chip swapping?  Easily done...

3.  Faulty components connected to an input or output. 

4.  Sometimes chips just die.

First check that the power supplies are right, measured against ground
(eg the sleeve of the output jack or a 0v test point).  

If the power is OK, try another TL072 and see if it's OK - they're so 
cheap it doesn't really matter if you kill another one.  If the new
TL072 doesn't get hot, measure the DC voltages on the output pins 
(1 and 7) and report back.



Steve