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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 2nd Dec 2021, 5:48 pm   #1
stevehertz
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Default Valve equivalent

I need a 442BU rectifier valve. The R-Type web site says that a UU5 is a replacement for it. But the 442BU is directly heated and the UU5 is indirectly heated. Is that ok?
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Old 2nd Dec 2021, 5:53 pm   #2
G.Castle
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Default Re: Valve equivalent

Cathode tube is connected to one side of the heater, so in that respect it will be fine.
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Old 2nd Dec 2021, 5:54 pm   #3
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Default Re: Valve equivalent

Quote:
Originally Posted by G.Castle View Post
Cathode tube is connected to one side of the heater, so in that respect it will be fine.
Please explain, thanks.
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Old 2nd Dec 2021, 6:04 pm   #4
G.Castle
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Default Re: Valve equivalent

A circuit that uses the directly heated valve has a separate transformer winding for the heater, so there's no problem with the uu5 that has the cathode connected to one side of the heater being used.

Sorry I accidentally hit post before finishing!
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Old 2nd Dec 2021, 7:45 pm   #5
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Default Re: Valve equivalent

And it'll give the reservoir capacitor an easier time on switch on since the rest of the valves will likely be coming on already as the rectifier starts to conduct. Directly heated rectifiers generally warm up faster than (indirectly heated) valves in the rest of the set resulting in a significant surge voltage on the smoothers.
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