Hello VHFers,
This is a follow up to my original e mail asking for advice on repairing
a Bird 6154 150 watt wattmeter/ load. I was hoping to find info on how
to proceed, but met with no success. My idea of finding a grizzled old
Bird employee turned up nothing. Info on the web is about nil. I ended
up getting a new 6154 that appears to work. That left me with the old
Bird 6154 that worked on the low ranges (5 and 15 watts) but was way out
of cal on 50 and 150 watts. The high range was way out of whack! With
nothing to lose, I dug in and have pretty much fixed it back to almost
perfect, Along the way, I learned a few things. I have noted that I am
seeing a higher indicated RF level above the 222 MHz band. 432 MHz is
reading about 0.9 dB too high. I am not surprised as I had to disturb
the parallel capacity of a capacitive divider network on the output of
the diode that sets the freq response. I had to unsolder a chunk of
siver plated brass that did double duty as part of the capacitive
network. When I resoldered things I made no attempt to get things back
in the EXACT position. Hey, I only had two hands and one of them is
shakier than the Waco Kid in "BLAZING SADDLES"!
When I took everything apart, I found that the capacitive probe had been
adjusted so far in that it fell off and was laying there inside causing
all sorts of errors. I re attached everything and soldered the assembly
back together. I can easily add a few pf externally and am hoping that
I can flatten the curve a bit. I'll write it up with pictures and
arrows. The 6154 can easily be re calibrated.
73
Dave K1WHS
On 2/29/2024 12:40 PM, David Olean wrote:
I know this is a long shot, but my Bird 6154 wattmeter seems to have
developed a serious problem and I need advice on fixing it. The thing
has two ranges with a crystal diode that plugs into two connectors. 05
and 0-15 watts works fine. The 50 and 150 watt position does not. It
is way out of calibration. It used to work FB. (?) I am looking for
some grizzled and crotchety old Bird employee who has the tribal
knowledge to effect the repair. To calibrate these things you poke a
small allen wrench into two openings on either side of the input
housing. There is a hole for each range. The low power side works
great and works fine. The allen wrench will turn something inside and
adjust the power setting. , but when I stick the allen wrench in the
other side, I can feel no set screw adjuster so I think some Bozo may
have turned the setting in too far and messed things up. I have to
disassemble it, but it looks all soldered together. The guts are held
in with a threaded locking nut. I can loosen that, but there is no way
to pull the innards out without unsoldering things. It looks real dicey.
I need to find someone who knows how they are built and can steer me
properly. If I can't find anyone, I am on my own and will hope for the
best, but we all know how that all works out.
HELP!
73
Dave K1WHS
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