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New Winter Project!




 
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October 25, 2021, 03:48:45 PM *
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Author Topic: New Winter Project!  (Read 993 times)
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WD8BIL
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« on: July 28, 2021, 08:47:49 AM »

Picked up my winter project last Saturday. It's a pair of 8005s driven by an 807 exciter. I have coil sets for 40, 20 and 10 and forms to build a set for 80/75.
It'll need a modulator since it was built for CW only. I'm going with 811As.

Good ol' buzzard AM on it's way.


* 2.jpg (295.12 KB, 1296x1728 - viewed 155 times.)

* 3Final.jpg (312.31 KB, 1728x1296 - viewed 113 times.)

* 4Exciter.jpg (307.52 KB, 1728x1296 - viewed 98 times.)
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WD8BIL
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« Reply #1 on: July 28, 2021, 08:49:26 AM »

A few more shots!


* 1Front.jpg (347.97 KB, 1296x1728 - viewed 131 times.)

* 5Power supply.jpg (353.19 KB, 1728x1296 - viewed 121 times.)
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KE5YTV
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« Reply #2 on: July 30, 2021, 07:03:00 PM »

Good looking rig. It needs some big jeweled pilot lights!  Grin Grin
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Mike
KE5YTV  Dallas, TX
"The longest trip begins with a stop at the ATM."
KB2WIG
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« Reply #3 on: July 30, 2021, 08:01:21 PM »



Windows!

It's got to have a window for those cold nights.

klc
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What? Me worry?
WD5JKO
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WD5JKO


« Reply #4 on: July 30, 2021, 11:12:18 PM »


I had a rig like that in the 1980's and it had 811's for a modulator.

The 8005 is an exceptional tube, and can be a very efficient class C amplifier.

Just boost the drive, increase the grid leak resistor, boost the drive, increase the grid leak...

Can get dam near 90% efficiency that way, deep into class C.

Downside is that the 8005 is very high perveance, and will peg the plate meter easily when off resonance.

The same tube is used in a highly sought after Macintosh tube audio amplifier, and therefore the supply is mostly used up and the price is sky high.

Lots of options to replace them....808, 812, 100th, 40T, 100T, V70D, and many more...I used a pair of 805's which ran beautifully as a class C plate modulated setup. High mu triodes like the 572B are not easy to be linear as a plate modulated tube. Stick with low to medium Mu tubes.

Looks like fun!

Jim
Wd5JKO

You need an overload relay.
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WD8BIL
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« Reply #5 on: July 31, 2021, 11:47:41 AM »

Thanks for the insight, Jim!

And Mike, I was thinking the same thing. Needs more ol' buzzard lamps!

I'll take the windows under advisement, Wigger. 2 spots I was thinking about was at the power supply to showcase the mercury vapors and, of course, the power amps 8005s!
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Patrick J. / KD5OEI
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« Reply #6 on: July 31, 2021, 11:41:47 PM »

Nice looking copper screens on the side vents. It almost looks like the builder extended the rack upwards. I wonder if you could add some height and move everything up enough to add a modulator chassis in the bottom? The top cover looks recoverable. Just needs a good beating with a mallet. Very nice project!

What are the plate-cap tubes on the exciter section? Could be the smaller 816 MV rectifiers maybe?

What are the three diagonally mounted tubes on the power supply? Could it be grid or cathode modulated by any chance?
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WD8BIL
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« Reply #7 on: August 01, 2021, 04:33:36 PM »

Hey Bear!

I haven't gone thru it much yet but when I find out the answers to your questions I'll letcha know.
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