[Collins] 312B-4 wattmeter query

[George Morton]

Check resistor(s) in couple unit.
----- Original Message ----- 
From: "Chris Kepus" <ckepus at comcast.net>
To: <geraldj at storm.weather.net>; <collins at mailman.qth.net>
Sent: Sunday, May 06, 2012 2:33 PM
Subject: [Collins] 312B-4 wattmeter query


>
> I have 2 B-4 units: one winged, one meatball.
>
> I haven't used either for some time so decided to test their wattmeter
> function before putting them "on-line".  Used a Valiant transmitter for RF
> power into a Bird into a 312B-4 into a Heathkit Cantenna. The results were
> very disappointing.
>
> The CCA site had nothing in the way of info to help.  The Collins list
> archives back through 2007 were also quiet on B-4 coupler problems or
> rebuilding. Google didn't turn anything up.
>
> Before I plunge into these units, I hope someone familiar with the B-4 can
> suggest some possible causes of the symptonms and/or the most efficient 
> way
> to trouble shoot my #1 and #2 B-4's problems.
>
> First up to test was #1, the winged B-4.  The meter pointer at rest (no
> power in) is a cat whisker above zero.  With power applied, the meter
> pointer moved to indicate 75 watts (200 W mode) while the Bird indicated 
> 110
> watts. Rapping the meter with a knuckle caused the meter pointer to 
> advance
> to roughly 140ish watts. When power was removed, the pointer did not 
> return
> to zero but stopped at about 30.  Hmmmm.  Rapping with a knuckle caused 
> the
> pointer to return pointing near zero.  Repeated this about six times 
> hoping
> the meter exercise would help but no joy. It appears the meter has a
> "sticky" movement.
>
> Second to test was #2, the meatball B-4.  At rest (no power in), the meter
> pointer is at zero.  With power applied (110 watts on the Bird), the meter
> pointer pinned above 200 watts (200 W mode).  Same result in 2000 W mode.
> Since the coupler is bi-directional with 200 and 2000 watt ranges for
> reflected power, I was tempted to input the power on the antenna side to 
> see
> what the meter would read. Nothing on the schematic looked to be in harm's
> way if the input/output were flipped.  Anyone?
>
> As Al, W8UT, said in a very similar circumstance in 2008, "Any help 
> greatly
> appreciated."
>
> Thanks es 73,
> Chris
> W7JPG
>
>
>
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