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[AMPS] temperature variable, varistor or globar resistor source wanted

To: <amps@contesting.com>
Subject: [AMPS] temperature variable, varistor or globar resistor source wanted
From: s.a.hall@btinternet.com (stephen hall)
Date: Tue, 12 Sep 2000 13:09:00 +0100
Hi Skipp and Group,
Dont know who manufactures these beasts but RFparts sell them....
I used two as filament inrush limiters in a single 3-500zg 50 mhz amp ....
One point to consider in using them is that if the supply is switched off
and them back on before they go cold they no longer limit the current!!!!

73
Stephen G7EUW

----- Original Message -----
From: <nospam4me@juno.com>
To: <amps@contesting.com>
Sent: Tuesday, September 12, 2000 7:03 AM
Subject: [AMPS] temperature variable, varistor or globar resistor source
wanted


>
> need: temp variable resistors information please.
>
> Hello gang,
>
> One of my Amplifier Research NMR amplifiers went belly up. This
> wide band unit is a very interesting design. Enough tubes are
> combined in parallel to bring the output down toward 50 ohms
> for driving the output.
>
> The fix turned out to be an open temperature variable resistor
> in the HV supply, used for current limiting.   Replacement of the
> part brought the amplifier back on line and all is well there.
> My hat is off to AR's support for sending me the part quickly and
> providing telephone help at no charge.
>
> My question is about the source of these parts. I remember
> Globar type and thermistors from old tv's but I haven't seen a
> newer design using these type of resistors in some time. Hence,
> I don't know who makes them anymore.
>
> The original temp resistor was labeled  Keystone with a 10 ohm
> value. The AR supplied replacement part was only labeled as
> SS  with the part value CL-10  printed on the side.
>
> Can anyone on amps supply me with the name of mfgrs still
> producing these type of parts..?  or any useful leads on these
> type of resistors..?  Is Keystone or Globar still in business..?
>
> For those not familiar with these items, they appear very similar
> in size and construction to the newer MOV's used for ac line spike
> protection.   Current through the part causes heating which then
> changes the resistance value.  Tube type tv's used them in the
> power supply for current limiting when the power was first
> applied.  A great early example of current inrush protection.
>
> anyway, thanks much.
>
> Replies to amps or myself direct would be greatly appreciated
> if you can help.  I'd like to buy a few to play around with.
>
> cheers
> skipp
> nospam4me@juno.com
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