Tube Amp Kit like the ones Zach and I have

Michael Chisena ka2zev at
Sun May 18 06:35:32 CDT 2008

  Here is the link if your thinking about one of those tube amps.
  Get to the web site and click 'Kits"
  When you get there click "Audio".
  It's the second one.
  This link is a photo from my shop in Kuwait.
  At the center of the work bench is a shelf, on top of that shelf is my little amp kit.
  On either end are two radio shack speakers I had shipped over from home.
  Most likely this was the only vacuum tube amplified  MP3 player in the entire country.
  People came into my shop just to see this amplifier run.
  The day that the Two Star General in charge of Army Communications Command  (CECOM) took the tour of our Generator shop was impressive. 
  Normally when the brass visit it's a whirlwind tour. 
  In, and right out again. 
  This guy who clearly had better things to do spent ten min in just my section alone. 
  He saw the amp. (I play light jazz when guys like that are due in, nobody gets offended with light jazz) and cracked a huge grin.
  Then I showed him some of the things done in the shop.
  This is a photo of a 15 and 30 kW static exciter. Think of it as a voltage regulator for military generators. It measures the output voltage and adjusts a magnetic field in the generator to keep that voltage stable.
  What happens is the actual voltage regulator drifts due to aging and it goes out of a fairly tight spec. 
  The module in the back, has no normal adjustment points on it.
  So most guys in my position would have to 'buy a new module' and slide it in.
  I cheated.
  The thing works because of the ratio of two precision power resistors. 
  There was no way I was going to get a ratio bridge and a buckets of resistors to match up.
  I drifted the resistors this way.
  See R24 and R27? See what I snuck under R 24?
  That drifted the unit back into spec.
  That saved you the tax payer 375 bucks for a new module. 
  I fixed the unit in about 15min and this will most likely work until the unit is junked.
  Did similar fixes to a bunch of different items.
  This is the one that got the Two Star.
  Similar item from a 100k generator. This voltage regulator module had a bad habit of blowing the little transistors you can see on the board top.
  The mechanics would bring in the whole static exciter, I would open that, test this regulator module separately, fix the failed transistors. 
  Stick it all back together. 
  Then test the whole exciter and kick it to the out shelf. 
  The boss types wanted me to make a little display for the general.
  So I put a full up static exciter and the USG price that was near 3500 bucks.
  Then I showed him a voltage regulator for about 600 bucks.
  Then I showed him two new transistors for about 7 dollars.
  So I asked him directly what do you want.
  The 3500 dollar fix, 
  The 600 dollar fix (all we were expected to do)
  Or the seven buck fix.
  Wink, nod, then the general smiled, told his assistant, a full bird Col. to give me a coin. That's the Army's way of saying, you done good.
  I rebuilt a lot of my own modules there simply because it made things more efficient.
  This item called an A5 Card were in short supply all over the world.
  People never tested them, saw the burn mark and 'assumed' they were bad.
  The truth of the matter was simply this. The burn mark was a 9 watt resistor, running at 9 watts and after a number of years it cooked the circuit board. Out about a hundred I worked on, this part got changed exactly once. Mine was the only shop to have a box of these available. Also whipped up this little relay tester for the silver can relays.
  The LED's were Bi Color (Red Green) and then the unit was buzzing along would appear orange. If one side or the other were poor, then the color would not be right. If the contacts were poor then the relay could not deliver the current to run the LED's. The event counter in the bottom was a way of keeping track. I usually stopped the test after 5k hits.
  The amp is still in service. It's on my workbench here in Herndon. Runs 24x7 and other than replacing the dual volume control that got trashed in shipping, it works like a charm.
  Later kids

"You are, what you do, when it counts"  
The Masso

"Gravity, the quickest way down"  
Mayor John Almafi

"You ever drop an egg, and on the floor you see it break? 

You go and get a mop so you can clean up your mistake.  

But did you ever stop to ponder why we know it's true? 

If you drop a broken egg you will not get an egg that's new?" 

MC Hawking
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