[R-390] Thermistor info for soft start?

[Tim Shoppa]

Tom Norris <r390a at bellsouth.net> wrote:
> What is the spec of the thermistor needed for the 390 and 390A to  
> give it soft start?  I had ordered a couple of the Keystone things  
> from Digi-Key several years ago, but am going to place a Mouser order  
> the next day or so and would like to get a couple from them for the  
> "new" stuff that just came in.

The one I use is a CL-80. Rated at a max current of 3 Amps (and a
R-390A with ovens off is about 1.5 Amps, with ovens on is a little
over 2 Amps) and cold resistance of 47 ohms. 

I don't know the official spec for max current of a R-390 but I'm
guessing it's similar or maybe just a little more.

Other ones with a similar max current rating will work too. As you go up
in max current rating, the cold resistance will drop and the current
limiting effect will go down. If you go too low in max current rating you
risk burning up something.

The CL-80 gets rather warm in operation - which means it is doing its job.
In my radio it gets to the point where it would be uncomfortable for me
to touch it more than just momentarily. And of course it is wired in the
hot AC lead so you gotta be careful not to touch the leads! Teflon is a good
thing for covering the leads.

Wow, if you need a couple does that mean you just acquired a couple
more 390/390A's? I'm jealous :-).

Mouser part # 527-CL80.  Digikey part # KC008L-ND. Can't believe I just
spent 4 or 5 whole paragraphs characterizing a single part!

Tim.