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Old 19th February 2008, 04:02 AM   #1
Salas is offline Salas  Greece
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Default NTC in High Tension PSUs?

Hello. Can I use NTC thermistors for high tension valve plate PSU inrush limiting? Say, 100 Ohm ones for 100mA at 1kV DC. If I use them in Cap -NTC -Cap Pi fashion will they burn? I see they normally have max voltage ratings in the under 300V range. But when 100mA would drop 10V on a 100R resistance, why I never see them in such applications?
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Old 19th February 2008, 01:09 PM   #2
Salas is offline Salas  Greece
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Bump.
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Old 19th February 2008, 05:34 PM   #3
Salas is offline Salas  Greece
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Well, I got some 150 Ohm NTC and tested them in series with a choke in between capacitor banks in a 1200V DC PSU for 100mA current draw. No sweat. They survive and do their stuff.
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Old 20th February 2008, 03:13 AM   #4
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Couldn't you try to do the limiting on the primary side?
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Old 20th February 2008, 12:50 PM   #5
Salas is offline Salas  Greece
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It is limited by 15 Ohm 4A NTCs anyway in the Power Trans primary side. Wanted to oppose the UHT DC a little bit more bcs the 845 DHT valve turns on its cathode very fast (gives out light instantly, different cathode chemistry than most) and I get a turn on mini thump. Not anymore, with small 150 R NTC opposing the inrush of DC to the final PSU filter sections. Another option is valve rectification, naturally delaying the UHT build up. But the amp I was modifying has silicon anyway. It blasts the SE OPTs and the solid carbon anodes too fast with UHT. And that had detrimental effect to the overall silence of the amp with time. Erratic noises could emanate. Now its a lady again.
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