Well, I opened up the AL-80A to see what had happened. I was stunned. I
expected to find a fried plate RF choke as Vic suggested. Instead, when I
removed the 3-500z, I first noticed the top inside surface of the glass had
a powdery substance on it in pattern not unlike the fins. Then I discovery
the really interesting new characteristic of the tube. There was a hole
clear through the glass as though it had been shot by a high-powered laser.
There are fine cracks around the hole and the glass had actually flowed
inward almost half an inch. Wow. Watch out for 17 meters on this baby. I
guess I'll replace the choke before I put the new tube in. I tried to order
a Taylor 3-500zg from RF Parts. They were back-ordered, so I accepted their
RFP Special which I suppose is their Chinese version.
Doug -- W4DXV
----- Original Message -----
From: Vic Rosenthal <rakefet@rakefet.com>
To: amps <amps@contesting.com>
Sent: Friday, June 11, 1999 10:32 AM
Subject: Re: [AMPS] Finally - a real amp
>
> Doug Person wrote:
> >
> > That seems quite a bit less than what the manual suggests. However, the
> > reduced power would hardly be noticable to anyone. I wonder what the
> > affects of SSB would be rather than full carrier. If I tune up the amp
> > using no more than the 400ma plate current and 65 watts drive, would
pushing
> > the power to 100 watts PEP input during normal SSB operations result in
> > additional stress on the 3-500z, or perhaps increase distortion?
>
> The single 3-500Z can be tuned and loaded to 550ma single tone (CW) for a
very
> short period in order to establish the correct operating conditions for
the peak
> of the SSB signal. It should then be driven by no more than about 65w PEP
to
> give about 1000w PEP output. Average plate current will be much less than
550
> MA. However, when operating CW, the amp should be loaded to 400 MA
maximum! I
> find that my SB1000 produces around 800 watts CW output with 400 MA plate
> current and around 125 MA grid current.
>
> > Now that I've gotton your input, I'm sorry to report that while tuning
the
> > AL-80A on 17 meters with 500ma ip and 150 ma of ig, A somewhat loud and
most
> > unpleasant noise ocurred within the amp after which there was no current
> > indicated for either ig or ip. Did I fry the tube?
>
> You probably fried the plate RF choke which has a resonance near 17
meters. You
> can order a replacement from Ameritron for about $25. The one made for
the
> AL80B works properly on the WARC bands. I have had one of these in my
SB-1000
> (which by the way is *very* similar to the AL80) for some time and it
works
> quite well on all bands, including WARC.
>
> 73,
> Vic, K2VCO
> Fresno CA
>
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>
>
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