[Yaesu] FT-450 Tuner acting weird

Doug dmcgarrett at optonline.net
Thu Mar 5 22:11:05 EST 2015

On 03/05/2015 09:23 PM, Tom Osborne wrote:
> Hi George
> It is the same with 2 different antennas.  With he tuner off, both of the antennas are resonant about 3530.  It was working about a week ago and then all of a sudden it just quit working on 80. Funny that it works OK on all the other bands.
> The funny thing is that I can hear the tuner trying to tune but the lights flicker and then go out.  When it gets done, the SWR is pegged out, even on the frequency the antenna is resonant on.
> This is the radio that I usually keep in my camper for summertime camping.  I just brought it in to check it out last week. 73
> Tom W7WHY
> On 3/5/2015 5:19 PM, George K5KG wrote:
>> Is this a tuner problem, or an antenna problem?  Try tuning it on 80 with a different antenna to isolate the problem.
>> 73, George k5kg
>> Sent from my iPhone
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All these automatic tuners operate by switching relays in and out. So there only a few possibilities, outside of digital corruption:

(I assume that the same directional coupler/detector is common to the other bands.)

One or more of the relay drivers is blown.

One or more of the lines that drive the drivers is not switching--possible digital corruption.

A tuned circuit that operates on the 80 meter band has gone bad--the capacitor open, maybe? (Look for bad solder joints, also.*)

One or more of the relays has become defective--I like this last option least; they should be good for a million or more operations.

I hope you have an oscilloscope--that would be my instrument of choice to look at the various possibilities.

*Since the tuner operates in a vibratory environment, with all the relays switching, a close inspection of the solder joints

is probably the _first_ thing you should do.

--doug, WA2SAY

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