variac?

mdub71 · 2490

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Offline mdub71

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on: February 03, 2015, 09:00:45 AM
I'm still assembling this kit, and I'm a ways away from the resistance tests and then actually applying voltage, but I have a question about the first time voltage is applied. Is it a good idea to use a variac for the first time voltage is applied? I'm wondering if the soft start components might not appreciate the variac? Thanks in advance. matt


Offline Grainger49

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Reply #1 on: February 03, 2015, 10:52:57 AM
A variac is more often used starting up older equipment that might have shorted power supply caps.

I'm not aware of anyone else who has started up Paramounts with a variac.  The soft start does its job very well.


Offline Paul Birkeland

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Reply #2 on: February 03, 2015, 01:41:19 PM
You can use a variac if you want to, but you won't get any useful voltage readings until you are at line voltages.

The soft start circuit provides a 2A3 grid bias during startup before the driver tube draws enough current to draw that voltage down appropriately on its own. 

-PB

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline mdub71

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Reply #3 on: February 04, 2015, 06:50:34 AM
thanks for the replies.
mw


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