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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 16th Jul 2019, 3:54 pm   #1
trickie_dickie
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Default Barretter

I admit to knowing almost nothing about these.

I am wondering if they can be used as a switch on surge limiter in a standard valve amplifier to limit the heater current surge at switch on?
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Old 16th Jul 2019, 4:11 pm   #2
Ed_Dinning
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Default Re: Barretter

Hi Richard, generally used on AC/DC sets to stabilise the current drawn and often instead of the dropper. They normally have a highish voltage across them when operating so not really suitable for low voltage heater chains.
A thermistor (NTC type) may do, especially the ones used on some SMPS units, but you would need to increase the heater volts source as the hot resistance of these devices is an ohm or so.

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Old 16th Jul 2019, 4:33 pm   #3
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Default Re: Barretter

Thanks Ed. I was thinking of putting it in series with the primary of a heater transformer. I have seen one on THAT website, quite cheap, Osram type 304 which was used with 300mA heaters but as you say, I'd need higher voltages.
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Old 16th Jul 2019, 11:02 pm   #4
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Default Re: Barretter

Is there any need to reduce switch on surges for ordinary 6.3V heater valves? They will always have operated that way in any period design......
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