Re: Tek 2215
Craig Sawyers <c.sawyers@...>
The symptom of attenuated and nonlinear vertical deflection pointed directly at the collector loadthe
printed circuit board itself was discolored from high temperature in the area under and aroundthem.
parasitic inductance of spiral cut film resistors. Why did Tektronix use carbon compositionresistors
there?Tek had a bit of a blind spot when it came to power dissipation in resistors on circuit boards.
They invariably mounted them tight to the board. So even if the part was operating inside its
dissipation limit, that power specification is always quoted by the resistor manufacturer "in free
air". Resistors which are dissipating a decent percentage of their power limit should be mounted on
spacers (which can be just a few mm) to ensure good air flow. If you put them tight to the board,
the contact is a hot spot which (a) discolours, or in some instances burns the board and (b)
compromises the lifetime of the resistor. Seen the same thing is some classic era Fluke gear too.