[Drake] L-4B

[fkamp at comcast.net]

David Harmon wrote:
> 
> Yes, yes, correct.
> 
> Regards
> 
> Dave Harmon
> NSRCA 586
> K6XYZ[at]comcast[dot]net
> Torrance, Ca.
> 
> -----Original Message-----
> From: drake-bounces at mailman.qth.net
> [mailto:drake-bounces at mailman.qth.net] On Behalf Of Jim W7RY
> Sent: Friday, July 23, 2004 6:26 PM
> To: W4AWM at aol.com; k7mks at comcast.net
> Cc: drake at mailman.qth.net
> Subject: Re: [Drake] L-4B
> 
> 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.
> >


Yes, Yes, Yes, maybe.   I swear.  You sound just like a French boss I
used to have.  His favorite expletives were 'but of course' and  'trust
me'.

No way was I going to 'trust him'.  The 'but of course' diddy fell flat
on me so I never gave that much thought.  Sort of like a 'up the tube'
expression you hear nowdays.

Yeah, I would not open up anything thing I did not feel comfort with.

However, it has always been a good engineering practice to bring up the
filaments before applying plate voltage.  No, there is no real need as
long as you can find tubes, reasonably priced, to replace the finals
that you destroy prematurely.

Regards,
Frank Kamp