After searching everywhere for a round-tuit I finally fired up my 34063
adjustable step up converter with the intention of testing a 555 pin 7 to
destruction.

I calculated the pot and fixed resistor on the 34063 for a maximum of 50V
but nearest preferred values it hit the stops at 58.9V, this is 3x the
headroom I need and frankly I expected the pin 7 transistor to go pop
somewhere around 32V.

In the light of this result there didn't seem anything to gain wasting a
chip by testing it to destruction.

In article ,
"Ian Field" wrote:

After searching everywhere for a round-tuit I finally fired up my 34063
adjustable step up converter with the intention of testing a 555 pin 7 to
destruction.

I calculated the pot and fixed resistor on the 34063 for a maximum of 50V
but nearest preferred values it hit the stops at 58.9V, this is 3x the
headroom I need and frankly I expected the pin 7 transistor to go pop
somewhere around 32V.

In the light of this result there didn't seem anything to gain wasting a
chip by testing it to destruction.

Did you test it at maximum expected temperatures? The breakdown voltage
in that case might be half as high as you hope.
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