[Drake] L-4B

[Jim W7RY]

Why does it matter??

The 3-500 is a VACUUME tube!  HV will not do damage to a tube that is under 
a full vacuume. Ever hear of a vacuum cap?

There is no good reason to keep the HV off the tubes during warmup. Do you 
know of a commerical 3-500 amplifier that does?

There is nothing in the Eimac sheets about keeping HV off until the tube 
has reached operating temp. The warmup takes about 2 seconds.


73
Jim W7RY

At 06:10 PM 7/23/2004, W4AWM at aol.com wrote:
>Hi,
>
>Placing a time delay in the L-4B and the L-7 for that matter is a very easy
>thing to accomplish.  While you are doing it, there are two other beneficial
>mods that can be made. These are a soft start circuit so the tubes light easy
>and a protection circuit for the irreplacable power switch.  A look at the
>schematic and the bottom of the amp will show how easy it is.  Be sure to
>disconnect the RF deck from the power supply and the power supply from the 
>line input
>before attempting to open anything up.
>
>73,
>
>John,  W4AWM
>
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