[Amps] Building an Amp 101

Jim Thomson jim.thom at telus.net
Sun Jan 19 20:56:05 EST 2014

Want some advice.   Just rack mount the amp.  Racks come in 19 inch ..and also 24 inch.   Loads of surplus racks available.    I went to my local metal supermarket and had em 
shear the front panel......using  .125 inch thick 6061-T6  aluminum.   19 inch wide x XXX  high.     The actual amp chassis is also made from .125 inch thick 6061-T6. 
Chassis  consists of separate front, rear and 2 x side panels.  Plus  top and bottom covers.  1 inch x 1 inch angle Aluminum, also .125 inch thick, also 6061-T6   is used
to connect all the various  panels together.   That way, any individual panel can be removed..and drilled from the inside, or outside.   10-32 SS machine screws  hold it all
together.   In my case,  I added large panels above the chassis, so when all done, the RF deck is one big box.   Chassis is 5 inchs tall...with the upper panels sitting flush to the
chassis.   Then when its all slid into the rack cabinet, it all ends up double shielded.  In my HB GG triode amps, I use a pair of broadcast variables and a tapped coil  for the tuned input.
I require enough chassis  height to fit the tuned input down there, along with all the other stuff.

The problem with a  pre-made chassis is.... they are a bitch to drill the side walls  from the inside.   If you try and jam stuff into a shoe box size cab,  you will have a helluva time trying 
to make stuff fit.   Get a tall enough rack cabinet and you can then put the HV supply and blower in the lower portion of the rack..where it belongs. Put casters  on the rack...and
you can now roll it around.    If you insist on having the RF deck sit on your desk..and eat up a huge chunk of your desk....at least put the heavy HV supply in a separate box......and
put it on the floor...also on casters.   With a rack mount setup, its much easier to substitute parts, and the layout is not as critical, since you have room to manoeuver.  You also
don’t end up with all the stray C associated with commercial built amps.  Keep the tank coils at least one half their diameter  away from top, bottom, and both side panels. A full diam
away is even better.   I use .028 inch thick  cu strap to interconnect everything....with machine screws. Don’t mess  with wire, it adds too much stray XL. 

Cu tubing is dirt cheap at any home depot.   I silver plate all the copper tubing and strap with this glop called ...cool-amp.   http://www.cool-amp.com/

Jim  VE7RF

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