Martin H. Eastburn wrote:
Wrong - lost the vacuum in the bottle. Likely a slow leak and maybe when
the internals
got hot it went through the seal. Rather common.

But if that were the case, why would it run for 15 to 30 seconds when
exposed to sunlight and then get "stuck" when the rotating part wobbles
a bit so the "hub" touches the vertical needle and sticks to it as
though it were magnetized?



If you think it is magnetized - the vanes are Al or Mg - for light
weight.

I don't doubt the vanes are made from a lightweight material but it
looks like they are attached to a small metal hub stuck on the bottom of
the glass nipple resting on the top of the needle. It's that hub which
"sticks" against the needle when it stalls out.

I understand that these radiometers work better when there's a very low
pressure in them than they do at a hard vacuum. Something to do with
having the right amount of air molecules inside which get heated by the
dark side of the vanes and give that side a bit of a kick.

I know I can buy a new radiometer for less than $12, but my curious mind
wants to see if demagnetizing would "fix" this one.

But if you
want - pass it through a loop that is passing AC.

One of those is the color TV - remember - when you turn on the TV there
is a Twang sound -
that is the coil getting a shot of juice upon power. Keeps the tube set.

Just put the unit on a wood table or such - at the center of the screen
and turn on the set.

Most won't let you do it more than once for a while... Just once or
twice is needed over time.

I'll probably make a coil or pull a scrap motor apart over the weekend
and see whether I can win this one with demagnitization. G

Jeff


--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."