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Author Topic: Looking for a Johnson 500 transmitter  (Read 696 times)

N8FVJ

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Re: Looking for a Johnson 500 transmitter
« Reply #15 on: January 10, 2022, 01:55:43 AM »

6 months ago he stated he would sell it to me for $2500.
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N2DTS

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Re: Looking for a Johnson 500 transmitter
« Reply #16 on: January 21, 2022, 12:12:40 PM »

Johnson's best looking transmitter ever!
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N2EY

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Re: Looking for a Johnson 500 transmitter
« Reply #17 on: February 08, 2022, 08:09:50 AM »

Some fun facts:

- Although called the Five Hundred, the transmitter actually operates at 600 watts DC input on CW.

- The literature refers to it as "the Five Hundred", using words rather than numbers, for some reason. Note the front panel lettering.

- The 811As in the modulator section are operated with 2000 volts on the plate even though the data sheets say 1500 volts is the maximum plate voltage for 811As. During development, EFJ contacted RCA and was told the bias arrangement in the Five Hundred was such that 2000 volts on the plates was OK.

Hope you find your Five Hundred. According to information published in Electric Radio years ago, only 865 were made.

73 de Jim, N2EY
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WA6III

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Re: Looking for a Johnson 500 transmitter
« Reply #18 on: February 08, 2022, 10:47:21 PM »


" ...  big question is does the VFO suffer from the same 'Chernobyl resistor' that is found in the Ranger I?  "

From the online BAMA manual;  R106, 18 K, 2 Watts.

https://bama.edebris.com/download/johnson/vik500/vik500.pdf

klc
Yup, it does. As does the Ranger II, Valiant and possibly others.  And it should be called the "Avalanche Resistor"! because as it gets hotter and hotter, the resistance becomes lower(which makes it hotter) . 

When it gets hot enough and the resistance goes below 5K or so (if it hasn't burned up yet)  The OA2 regulator tube begins to overheat and "cook" everything around it, which literally "chars" the bakelite board......and everything else near to it.  By then the resistor is probably smoking and burning

Johnson put a 2W carbon in there when it should have been a 5W (or more) But no one could have thought that these old radios would be anywhere but in a landfill after 60+ years!!!

Some people move that resistor out of the VFO cabinet to below the chassis. 

In my Valiant, I used a 22K 7W ceramic and left it in the vfo cabinet. It barely gets warm now.




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N4MQ

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Re: Looking for a Johnson 500 transmitter
« Reply #19 on: February 26, 2022, 05:58:12 AM »

ROAD TRIP !!!!!!!!!!!!!!!!!  I HAVE FOUND A PAIR OF 500s AND ONE POWER SUPPLY, YIPPIE.  GOING TO GET THEM TOMORROW, THIS IS GREAT.  At 77 this will finish my johnson line-up and my last boatanchor rig.  The hunt has paid off, more to follow,Enjoy Woody
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AC9QC

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Re: Looking for a Johnson 500 transmitter
« Reply #20 on: February 28, 2022, 05:07:04 AM »

Post pics :)
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N4MQ

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Re: Looking for a Johnson 500 transmitter
« Reply #21 on: February 28, 2022, 05:15:37 AM »

posting pictures here is tough and I have not had success. woody
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N8FVJ

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Re: Looking for a Johnson 500 transmitter
« Reply #22 on: March 07, 2022, 05:12:31 AM »

Ron stated you only offered $1200 for the mint Johnson 500.
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N4MQ

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Re: Looking for a Johnson 500 transmitter
« Reply #23 on: March 08, 2022, 04:44:49 AM »

That is not the case as I know the value, I was told that he PAID $2500 for it, and wanted to use it and was not ready to sell at that time.  The rigs I just bought sold at several times the 1200$ you referenced, and I feel fine with that.
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N8FVJ

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Re: Looking for a Johnson 500 transmitter
« Reply #24 on: March 10, 2022, 01:43:14 PM »

Ron does not use the Johnson 500- never had. Once in a while he uses his Globe King 500 that he has owned since about 1970.
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