[Boatanchors] Tube Shields

[Rob Atkinson]

Hi Jim thanks; I have two audio amps that use the 6BQ5 (not AQ5) and
all I know is they get very hot so I run a fan on each one blowing
across the chassis.

73

Rob
K5UJ

On Sat, Nov 26, 2011 at 7:48 PM, James Liles <james.liles at comcast.net> wrote:
> Hi Rob:
>
> The IERC tube shield does touch the tube and some use fingers and others
> spring loaded plates.  Here is a case and point as to their effectiveness.
> The SR-2000/SR-400/SR400A and a whole plethora of radios use the 6AQ5A for
> an audio amplifier.  The SR-2000 specifically and most others run that tube
> to maximum parameters.  Shoot it with an infrared temperature probe and you
> will find it at 420+ degrees and mean time to failure fairly short.  A great
> odometer or hour meter for the SR-2000 is the degree that the relay next to
> the 6AQ5A is charred.  Install an IERC shield and the tube will true out at
> 270 degrees and you won't have to replace it again.  There are two switching
> circuits in the SR-2000/SR-400/SR-400A that use the 6AQ5A cathode potential
> to perform gating: the heterodyne oscillator to the transmit mixer and
> balanced modulator to the second if amplifier.  They expect +1.5v and +16.0v
> and if the tube cannot make at least 14.0v the receiver will provide you
> with a myriad of new birdies and deteriorated performance.
>
> Antique electronics supply has the various sizes and configurations at
> fairly good prices.  Note:  You don't have to replace the tube socket: they
> also have the sleeve to mount it on the existing socket --- just drill the
> rivets out and install the sleeve over the tube socket.
>
> Kindest regards Jim K9AXN