Alpha is very clear on advice... Run Alphas on 220VAC lines and skip the
CW/lower voltage position and run it in SSB/hi all the time.
Less that that, you are falsely trying to baby your amp (or just need a new 220
line run). Alpha also says tune for max smoke out.
Charles Harpole
k4vud@hotmail.com
----------------------------------------
> From: rex@lint.mv.com
> To: jerry@tr2.com; amps@contesting.com
> Date: Wed, 20 Jun 2012 13:17:35 -0400
> Subject: Re: [Amps] Misc Alpha thoughts
>
> " Alas, all the 110V on this floor of the house is on the same phase."
>
> A trip to the breaker box and a swap of breakers on the right phases might
> save you "a trip to the count".
>
> -Rex-
>
> Rex Lint, Consultant
> 26 Brek Drive
> Merrimack, NH 03054
> PH: 603-860-7651
>
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of Jerry Kaidor
> Sent: Wednesday, June 20, 2012 1:28 PM
> To: amps@contesting.com
> Subject: [Amps] Misc Alpha thoughts
>
> Hi Guys,
>
> Just had my first QSO with the '78. There was a special event station
> calling CQ. I answered him barefoot, he didn't get my call. Then I pressed
> the "SSB" button on the Alpha and called him again. No problem. "What did
> you do?" he asked. He said I want from 5/6 to 20 over S9. Sounds a little
> extreme actually, but that's what the man said.
>
> Nice amp. Very solid. Using the bandpass feature, no peaking and
> tweeking whatsoever. Fan's a little loud. Also, I can feel it through the
> operating table. I see Alpha sells a new fan for $65, I might indulge. I
> could try taking the existing one out and renewing the foam packing or
> somesuch but it's a bit of a bear to get at it, and I
> think I might as well have a new part in hand when I take it apart. I
> wonder how hard it would be to vary the fan speed? I'm thinking two speeds
> - one for transmitting and cooling down after transmitting, and the second
> speed for receive/idle. A resistor across a relay....
>
> This amp really wants 220VAC. It does work, but only gives about 900W.
> I think it's because the HV regulation is not good running off 110. The
> 2200V sags down to about 1600 under load. Last night I thought of trying my
> "cheap & dirty 220" trick. You find two 110 sockets that are on opposite
> phases, build a box that plugs into each, and has a 220V socket.
> I actually built such a box for welding in the field. It has a 220V 15A
> breaker in it. That guarantees that in case of an overload, both phases
> will be turned off - the 15A breaker in the box trips before the 20A breaker
> in the building. Alas, all the 110V on this floor of the house is on the
> same phase. So it looks like the procedure will be to go to the County and
> pull a permit and install proper 220. I don't see that happening before the
> end of the year, I have so many projects lined up.
>
> Those three little unobtanium tubes are worrisome. Some people have
> replaced them with 2 3CX800A7 tubes. Which actually raises the plate
> dissipation from 1200W to 1600W. The input and output stuff all works, and
> the amp tunes the same. Even uses the same tube sockets. Might have to
> repeak the bandpass networks. The only complication is that the 3CX800A7
> has a different filament voltage. And the box is really REALLY full. I
> don't see where another transformer can be shoehorned in. Yet people do it.
> Alpha's blog suggested mounting it in the RF section. I guess a transformer
> doesn't care about being immersed in an RF field - as long as nothing arcs.
> Would have to take care to bypass it good so I don't feed RF back to the AC
> circuitry.
>
> Even though the amp works fine now, I will be accumulating parts to do
> this mod. I predict that some years from now, if and when these little
> tubes actually die, the 3CX800A7 will be the same unobtanium as the 8874's
> are now. So better get'em while the getting is good. As soon as the toy
> fund recovers from this purchase. Right now, it stands at $0.00.
>
> I was planning to get by on 110V by using the CW position. Have changed
> my feeling on that completely. The CW position is harder to drive, and you
> tend to run more grid current. So SSB position it is.
>
> - Jerry Kaidor, KF6VB
>
>
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