Arnd Gronenberg wrote:

The information regarding the temperature calibration is very helpful. I
found a replacement thermistor, which seems to be suitable: 83K @ 25C,
10.24K @ 80C, reaction time 0.7s, size 1.5mm diameter.

As the HP 10544A uses an AT cut crystal I assume that I have to
calibrate for a frequency minimum (according to the above mentioned
website). As the HP 10544A contains a 10 turn variable resistor instead
of a hand-picked resistor, calibration should be quite straight forward.

If your oven works at 80 degC, it contains an SC cut crystal and not an AT.
AT crystals have their optimum temperature at abt. 28 degC, they are close
to useless at 80 degC.

73, Gerhard dk4xp