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This is 400 lbs of Nothing




 
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WA1QHQ
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« Reply #25 on: January 24, 2014, 11:16:24 AM »

I see an Electric Radio article in the future.

WA1QHQ
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Tom W2ILA
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« Reply #26 on: January 25, 2014, 10:18:43 AM »

Skip the step of building a power supply.  Graduate directly into a proper Scout Car or other vehicle destined for wartime destruction and use the 653 to order coffee from a drive-through.

 
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KD3ZK
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« Reply #27 on: January 29, 2014, 12:56:54 PM »

Check out this working SCR-506 in the Philadelphia area.

http://www.youtube.com/watch?v=Y38rO2tXRjI

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pa0ast
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« Reply #28 on: January 30, 2014, 12:36:45 PM »

Or this one.  http://www.dse.nl/~vrzaob/wc52/radios.html
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WU2D
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CW is just a narrower version of AM


« Reply #29 on: January 31, 2014, 04:47:53 PM »

The bestial BC-653A power supply is finally complete and bench tested under loads. All three supplies appear to be excellent with all kinds of capacity. The outputs are 12 VDC at lots of juice. 500 VDC at significant capacity and an 1110V HV supply made from two MOTs.

I had to play with the HV by boosting the primary with an unused winding on the MV transformer. This trick got me from 975V to 1110. Next I have to make the cable between the PSU and my new Jones connector. The second switch with the red lamp is the HV ON switch which is a step start of about 1 second. Both MV and HV have floating ground (only the 12V is actually grounding); they all see reference to ground at the radio.

You may see the purple wire on the top picture going up to the MV transformer to get a few more volts for the MOT primaries. Both the MV and HV chokes are in the negative lead and the HV has a 25 mA bleed. The MV transformer is one of those cheap but beefy 150 kVA control transformers. It had a 400V and 18V winding on one side and 120V winding on the other. The 12VDC is also based on a an L filter with a homemade choke and 33000 uF and a 150 Ohm Bleed. It is off the four paralleled  5 Amp transformers. The rectifier is off an old ATX power supply; a heat sunk dual Schottky high efficiency rectifier.

My construction practice is adequate, fairly safe but not super pretty. That said, my last really big supply build was for my ART-13 and it is just as good as when I built it in 1993. I also plan on using this supply for the BC-191F project which will be coming sometime this year.


* 653PSUFrnt.jpg (613.25 KB, 3433x2381 - viewed 356 times.)

* Beast1.jpg (698.13 KB, 3913x2729 - viewed 371 times.)

* HV_1100.jpg (858.41 KB, 4043x3092 - viewed 474 times.)
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These are the good old days of AM
WU2D
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CW is just a narrower version of AM


« Reply #30 on: February 01, 2014, 04:53:36 PM »

It is ALIVE!

No meter working but on Band C preset I got a strong signal and brought it right down to 80M. The VR tubes lit up and the relay keys nicely. Pop goes the fuse after I started to get some power out. Checking I only had 3A fuses in as a safety precaution. So I went up to 8A fuses and dove in.

How to match this beast? Look at the schematic in the output section. They were trying to load into a 12 ft whip like on a boat! The output network seems to be a parallel tank with a loading coil coming right off the top! This is not going to cut it for 50 Ohms. In a panic move I decided to shotgun in a split C output from the antenna post to a 60pF doorknob to the center of the coax and a 500 pF doorknob to ground. Then I fooled with the loading coil. It is sharp with just one turn up or down effecting the output, but I got 85 honest Watts out into 50 Ohms with the thing. The CW note is pretty good too. Lots to do before I declare victory or try it on suppressor grid AM, but very encouraging since the CW specs say 60 to 90 Watts out depending on the frequency.


* BC653A_Schem.jpg (1139.92 KB, 2850x1969 - viewed 399 times.)

* ITIS ALIVE!.jpg (695.74 KB, 4467x3074 - viewed 376 times.)
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These are the good old days of AM
AJ1G
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« Reply #31 on: February 02, 2014, 10:42:09 AM »

While looking at the You Tube video links provide above, I came across this one about the Collings Foundation's B-24J, looks like they have restored the BC-375 and  BC-348 to operating condition.  Check out how they light up a fluorescent tube in front of the row of 211s!


http://www.youtube.com/watch?v=G1S_amgpvVw

Glad to see they have got the old sets running, they have pretty much been static displays only for many years.
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Chris, AJ1G
Stonington, CT
WU2D
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CW is just a narrower version of AM


« Reply #32 on: February 03, 2014, 08:58:36 AM »

AM - not kidding. Last evening some folks gathered at 2200 on 3705 kHz (Sundays) for the low power long range recon net AM version (75M moose and squirrel net ). I had the beast on 3570 on the OMRN CW net (all covers off on floor) doing 90 Watts for its maiden voyage on the air. It has a sweet CW tone. The 807 makes for an "adequate" buffer, for the 814's - that is for sure! By the way - all original tubes. Have not touched or adjusted a thing.

So I tuned one of the preset channels up to 3705 into a dummy load and got 5 Watts out. I had to kill HV and move the tap on the loading coil exactly 2 turns up, readjust the tuning (they call it coupling) cap and bingo 85 Watts. Then I set the transmitter to AM and the carrier dropped to just over 20W. I plugged in a T-17 and by heavens I could hear myself in the receiver. Now this is suppressor grid modulation of a pair of 814's. Flipping to antenna, I yelled for AJ1G, Chris and he came right back.

Still lots to fix and align , but I am getting close to declaring victory.
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Patrick J. / KD5OEI
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« Reply #33 on: February 08, 2014, 05:38:10 AM »

Do you  mind if I put the schematic on my BC653 web page? Mine is very poor.
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Radio Candelstein - Flagship Station of the NRK Radio Network.
WU2D
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CW is just a narrower version of AM


« Reply #34 on: February 08, 2014, 09:07:31 AM »

Go ahead and stick that schematic on the site. I made it by scanning the schematic from the manual; piecing the two scans together as best I could in Photoshop, and cleaning it up and adjusting the contrast. Not perfect by any means as I just have a small scanner.
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These are the good old days of AM
WB6NVH
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« Reply #35 on: February 08, 2014, 04:16:24 PM »

There is a faily complete article about this setup in a QST printed during WW2 giving it glowing reviews.  I think it was a 1942 issue which kind of surprised me as I thought that they wouldn't be printing information to let the enemy know what we were using, but maybe it was common knowledge by then. These seem to be really rare today, at least the transmitter and the accessory pieces.  Maybe because the weight turned off surplus buying hams or maybe they just didn't make too many of them. 

Great to know another one gets on the air 70 years later!
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Geoff Fors
Monterey, California
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