Having a bit of a RF power meter check up, I have (HP) 436A which uses the cheaper diode power heads 848x,
And a 432A which uses 478a thermistor type, I have one 478 that works another appears superficially dead.
I have just discovered that the 478a is a current part from KS - FOR AUS $8800!!! WOW,
That is ok, you can buy the 4 thermistors all bound up - in an insert for just $3300!
These thermistors are less than 1mm in diameter. I think I will list the working 478a in my final will and testament!
(ok you can buy 'probably' working ones for USD $270)
Rob