In my experience running for long periods of time has a tendency to overheat
the cavity. The supplied fan is to small (and loud) a bigger fan does help. I
would not spend money on the Russian tube if your 8930 is still good. Like I
said cutting the thing apart and running a bigger fan is the way to go. Key
down at a reasonable level in digital modes should be OK, again they were
designed for 50 watts.
K6KWQ Dick "12 Volt radios are for wimps, real radios can kill you" Still can't
make it go QRO with "More Power"
----- Original Message -----
From: KY1K
To: RICHARD GEORGE ; amps@contesting.com
Sent: Monday, September 13, 2004 5:00 AM
Subject: Re: [Amps] AM-6154 questions
I read the original post again. When I read it originally, I never thought
he turned it on and let it cook at 150 watts over night. But, maybe that is
what he did.
I hope to run one of these someday and have an interest in digital modes
(which means running key down for 30 seconds to 2.5 minutes). If I upgrade
to the bigger tube, will these amps run keydown for long periods (limited
by the tube) or does the power supply/cavity give up first?
In previous discussions of these amps, I've never heard anyone who used
them complain about not being able to run key down for extended periods.
Thanks all.
Art, KY1K.
At 03:17 PM 9/12/2004, you wrote:
>I would have never left it running for that long. This amp was only
>designed for 50 watts out. You probably overheated the cavity and after
>you left it off and it cooled down it now is making contact in the cavity.
>In my experience with these amps, leave the 8930 in place. You said you
>only wanted 150 watts. Did you note the difference in anode size when you
>changed the tube? 350 watts output is about the safe max on SSB. I know
>you here about 500 watts out, I can guarantee not for long, and it will
>sound terrible. I modified my last one by cutting the power supply away
>from the cavity and making it 2 pieces. Much easier to transport to
>mountain tops, and you can replace the noise maker 400hz fan with a bigger
>ac fan for more cooling.
>But again opinions are like a## H#### every one has one.
>
>
>
>
>
>K6KWQ Dick "12 Volt radios are for wimps, real radios can kill you" Still
>can't make it go QRO with "More Power"
> ----- Original Message -----
> From: Web Williams
> To: amps@contesting.com
> Sent: Sunday, September 12, 2004 10:58 AM
> Subject: [Amps] AM-6154 questions
>
>
> I thought I'd come in here begging for an answer, since I have not
> been able to turn up anything on the internet about an AM-6154
> VHF amplifier that I have.
>
> It's been working fine with an 8930 for about three years, but
> seeing all the improvements being raved about, I felt compelled
> to try a Svetlana 4CX-400. The tube swap was uneventful, as
> well as the tuneup with the new tube. Everything looked just
> fine! I was advised by the tube seller to "keep it down" for the
> first 24 hours or so, and he provided me with a procecure for
> tube burn-in. I had no way to do it the way he described, but
> he said alternately that I could leave the amp turned on for 24
> hours, and if there were any problems with the tube being gassy,
> or having a bad seal, it would likely show up.
>
> After checking for output (I did want to see if it was going to work)
> I tuned up at about 150 watts for a couple of watts in, and everything
> looked great! I assumed (hope I was correct) that this minimal power
> level would not really stress anything. I then left the amp turned on for
> 24 hours to burn in.
>
> The next morning, I went to my shack, and checked everything, and it
> seemed just fine. Same 150 watts output (I had not tried to go for max
> smoke yet- I have an ARR preamp in line that is only rated for 160 watts
> pass-through). I heard a station on, and called him. My wattmeter is
> situated where I cannot see it when I am speaking into the microphone.
> After several unsuccessful calls, I looked over at the meter, and it was
> dead on zero when I was transmitting!
>
> I made an assumption that I blew the new tube, so I quickly put the
> 8930 back in. Still no output (after retuning to proper positions on all
> dials).
>
> Both fuses on the front check good with my DVM. Plate voltage goes
> to mid-scale (not sure how this unit was set up, I didn't do it, and don't
> know who did). Screen voltage is 40 (about 3/4 scale) and grid voltage
> goes to 50 (not pegging the meter, but almost). Heater voltage puts the
> meter at 28. Still no output!
>
> I let the amp sit for about a week, went back to it, and still no output.
> Three weeks of sitting there without me even touching any controls
> I went back to it, and it's fine! Other than turning it on and checking
the
> voltages by spinning the test switch through the various test positions,
it
> seems perfectly OK! (Didn't put the 4CX400 back in it.)
>
> Does anyone have any ideas as to what to check? I'm totally lost!!!
>
> Thanks, -Web Williams in Myrtle Beach, SC
>
>
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