[Boatanchors] FS: EF Johnson 250-39 Electronic T-R Switch
bob.groh at gmail.com
Wed Jun 29 23:49:34 EDT 2016
Picked up this little gem a number of years ago. The case (which was a
'chromed' type finish had gotten pretty bad so I repainted it (rather
nicely, I think!). Started a minor restoration on it and then put it back
on the shelf. Recently I took it off the shelf and finished up the
restoration which was really minor - put a new 3 wire ac cord on it and
then did a slow and careful power up (10V steps over a day or so) to reform
the electrolytic. All the voltages check out on the money. The inside is
in great condition but I don't have an operational transmitter to actually
test it. Frankly I really don't expect it not to work.
I do have a web picture album showing the finished unit along with some
before pictures - email me and I will send you a link (links don't seem to
survive going through this reflector).
Basically the EFJ 250-39 is a single tube 'blocking' amplifier - the
transmitter and antenna are direct connected and the a 6BL7 connects that
junction to a coax connector which goes to the receiver. Works from 3.5 to
30 MHz at power levels up to 4 KW PEP. In receive, there is actually a bit
of gain. I don't know how much isolation there is when the transmitter is
on. I used a similar unit (from DowKey) when I was a Novice 'back in the
day' (1958 or thereabouts) with an Eico 720 and S-40B. I have a printed
copy of the pdf version of the manual (from BAMA).
Price: $30 plus $16 shipping (US only). If interested, drop me a line.
Bob Groh, WA2CKY
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