[Boatanchors] Johnson Matchbox 275W

[Clarke, Tom AIR4.0P NATOPS]

 Hi Larry,

I have had two of these and both had been "modded" to disable the
internal TR relay.  This necessitated the use of an external relay, as
the relay contacts were jumpered to TX permanently.  Another common
"mod" was to put an SO-239 next to one of the beehive insulators for
coax fed antennas.  I was able to rewire mine to original and the
antenna relay worked as designed.

73 Tom/W4OKW

-----Original Message-----
From: telegrapher at q.com [mailto:telegrapher at q.com] 
Sent: Wednesday, July 27, 2011 2:34 PM
To: boatanchors at mailman.qth.net
Subject: [Boatanchors] Johnson Matchbox 275W


In hooking my 275W matchbox to the Viking II and back to the R-388 i'll
be using with it i noticed that i could not get any signal thru it in
the receive direction.  Well one thing is that the receive side is 300
ohm out to the receiver.  Hmmmm, a TV 300/75 ohm balun fixed that.
Still no signal.  Why does it have the extra coax connector on the back
side.  What was it put there for?  Better pull it apart and see what is
going on.  True to Johnson products, there are somehwer close to 10, 000
screws in it.  Well not really but if you've taken the bottom off the
Viking II, and i suppose the Viking 1 is similar you know how to remove
lots of screws.   Back to the topic at hand.  When i finally got the
cover off the problem became pretty apparent.  On the screw terminals
for the antenna lead to the receiver, nothing was attached to the
supposed hot side.  The coax connector that was added, apparently part
of a mod goes to the common leaf on one side of a 3 pole relay.  Both
contacts whether operated or released runs the center contact of the
coax connector to ground.  Wonder what was accomplished there?  The RF
input connector which goes to another side of the relay was totally
bypassed so the tuner was in the line all the time and could not be
switched out.  Simple jumper removal and addition here will fix this.

Why or what was the purpose of the mod to add the coax connector and
were there other changes included?  I've got the documentation off of
Edebris or the Bama site but there is no mention of any mods.  I think
i've heard from other sources that the 275W matchbox did have a coax mod
done to it and i think it is for the receiver side but not sure.  Any
clues from other users that have one of these?  Otherwise it appears to
be a very nice clean unit.

Larry
W0OGH