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[AMPS] Alpha 374

To: <amps@contesting.com>
Subject: [AMPS] Alpha 374
From: stevek@jmr.com (Steve Katz)
Date: Wed, 6 Mar 2002 07:46:50 -0800
> Ok guys here is another problem for ya! The manual tuning on 10 &15 mtrs
> doesn't work very well ; about 250 watts out and tubes get real warm
> trying to tune these bands for some reason. All the other bands tune up
> no problem in the manual mode. I have checked both capacitors and no
> problems. The amp tunes fine in bandpass mode all bands. If I fool
> around with tune too much it starts to smell like its burning a
> resistor, but can't seem to find same. Chuck KG4EOG
> 
> 
        ::I've seen this in the 374 before.  The burning smell is likely to
be a small RF choke that's between the HV PS and the "big" plate RFC (it's a
much smaller one, molded), and when it opens up, you'll know it.

        ::When you say you checked "both capacitors," are you talking about
just the tunable plate & load caps, or others?  The 374 is loaded with lots
of components in the plate tank...I've also burned the contacts on the
bandswitch more than once, which requires a bandswitch disassembly, wafer
replacement, and reassembly.  Not a hard job, but be careful.  The bsw
contacts on the 374 seem to just dissolve eventually for no reason other
than age and lots of use at power levels it probably was never intended to
run...my old 374 (emphasis on old) can run 2kW output, but was designed &
built to run about half that.    -WB2WIK/6



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