Strange 555 failure

throbscottle

Well-Known Member
Just having to replace a 555 timer where it looks like the middle one of it's 3 internal resistors has failed S/C, or something else has blown between the 2 comparators. It was fairly new too - genuine TI bought from RS Components some years ago. Now has nearly the same resistance between it's CV pin and Vcc or Gnd.

It's being used as astable to produce a PWM signal (around 2KHz) with 5v supply. The only action being seen by the CV pin is to be connected periodically (period of several seconds) to 0v by a transistor. It's currently also got a decoupling cap attached to it but I might take that out.

Do you think something could have caused this to happen, or have I just been unlucky?
 
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