I've owned an MN4C with B1000 for about 6 months, and really like this tuner.
Recently, the settings on reactive and resistive changed drastically, the tuner
insisted on being switched to the 40M inductance to tune at all.
The tuner worked one weekend, then when attempted to use it the next weekend it
wouldn't match the antenna. Thinking the tuner couldn't possibly be the issue,
rebuilt the antenna without improving anything. My MFJ949 has no problem
matching the 88' doublet and surprisingly the settings are nearly the same as
for an 88' doublet at my other QTH. This proved to me that the Drake tuner is
broken.
I have gone through the tuner and cannot identify the problem. The SWR bridge
is working fine, the SWR meter on the rig confirms that the readings are
correct. I have used a capacitor bridge to confirm the capacitance values, but
replaced the caps on the band switch anyway thinking perhaps one or more were
breaking down on RF. The tuner seems to function properly on 20, 15 & 10 band
positions. But on 40 and 80 it cannot match the antenna. I have reflowed all
of the soldered connections, checked for shorts and opens without success. The
inductor has no apparent damage. The balun is undamaged, and even connecting
an outboard balun to one of the coax outputs doesn't improve the behavior.
The only discoloration noticed anywhere was the hot lead of the 160M capacitor
which was blackened. That and the rest of the caps have been replaced and I
see nothing else that would explain the tuner's behavior.
Any ideas would be appreciated, I'm nearly to the point of totally "rekitting"
the tuner because the only thing I can imagine is that the band switch now has
some flaw that is impossible to see while inside the tuner.
I know this isn't a TR-4cw, just a simple tuner, but I really like it and want
to restore it to operation somehow.
73, Curt KB5JO
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