Bill,
I made that claim on this very board (or was it the Heath amps board) a
few months back. You cannot imagine the noise I got out of that. But I
had similar results as you did. Painting that compartment black sure
does make a big difference.
And while Carl has the magic touch of getting those 572b to sing, they
died fast and frequenty in my hands, regardless of what magic potion I
tried. I'm sure under SSB use, they do fine. But if a guy wants to do
RTTY, this definately is NOT the tube to use.
Love these GI7Bs though. They just keep going and going and going.
73/jeff/ac0c
Bill Fuqua wrote:
> the 572B has 160 watts plate dissipation each.
> A pair around 320,.
> Now saying that there are some issues about the tubes and plate
> dissipation.
> These are radiation cooled tubes needing air blown on the plate and
> pin seals to
> keep them from cracking.
> Oddly enough they are usually surrounded by good shinny aluminum
> which in turns
> reflects a lot of the infrared back into the envelope. If the inside
> of the cabinet was painted
> black the tubes' plates would be cooler. We illustrated this the other
> day when one of my
> fellow employees tried to pull a fast one on someone after I explained
> why the "laser" thermometer
> read a temperature above room temperature. The thermometer , the laser
> is just used for pointing,
> was reading something near his body temperature. It was seeing his
> reflection in the aluminum
> plate. The emissivity of shinny aluminum is very small but it is very
> reflective. He told a fellow co-worker
> that something was wrong with the thermometer because it read almost
> room temperature when he was
> looking at the bottom of a cold Pepsi can. But seemed fine when
> measuring his body temperature or that
> of objects in the room. Well the co-worker was me, I guess he forgot
> that I had explained it to him a few
> years ago.
> Glass is usually fairly small in the near infrared because it is
> transparent. The emissivity not only is
> a measure of the ability of an object to emit radiation but also to
> absorb it..
> I believe it was the T-368 transmitter that had an aluminum
> chimney around the 4-400A but it
> was black anodized. I guess they they did not want to use glass. For
> the same reason you have flat
> black plates in these tubes.
>
> Anyway, I think a lot of amplifiers with glass envelop tubes would
> be more reliable if the
> the metal surfaces around the tubes were black.
>
> Well, I have to get back to work. I am working a bit late tonight.
>
> 73
> Bill wa4lav
>
>
> At 06:20 PM 3/12/2009 -0400, you wrote:
>> Carl,
>>
>> Can you send us some of whatever is in the water up there? Because the
>> SB200's in this part of the world are sure in need of that magic elixor.
>>
>> What's the plate dis of a pair of 572b? Something like 360w? Maybe
>> that is the answer to my question on the other subject of anode dis
>> limits...
>>
>> Clearly a sample size of 250 sb200 converted to 6m service is an
>> extreeme case (given the tubes start running out of gas at 30mhz more or
>> less) - and a large sample set of 200 statistically is very significant.
>>
>> If that tube will work at 2x the plate dis in the north east, then I
>> surely should be able to get the similar multiplier from my conversion
>> project here in the fly-over country.
>>
>> 73/jeff/ac0c
>>
>> Carl wrote:
>> > My 2 cents anyway. :)
>> >
>> > Yep, I agree with the above<G>
>> >
>> > In my experience with converting around 250 SB-200's to 6M I can
>> > unequivocally say that a majority still have the original Cetrons
>> > installed and will run 700W + key down on 6M on a 240V AC line. A bit
>> > less on 120V.
>> >
>> > Your milage may vary.
>> >
>> > Altho I feel the 4 x 810 project is a wasted effort it is possible to
>> > do it with 4 x 813's and cover 160-10M.
>> >
>> > Carl
>> > KM1H
>> >
>> >
>> > ----- Original Message ----- From: "Jeff Blaine"
>> > <keepwalking188@yahoo.com>
>> > To: "George Knight" <gkve3ltu@sympatico.ca>
>> > Cc: <amps@contesting.com>
>> > Sent: Thursday, March 12, 2009 3:21 PM
>> > Subject: Re: [Amps] 810 Amplifier
>> >
>> >
>> >> George,
>> >>
>> >> You may want to consider a trio of GI7B (less complicated) or
>> perhaps a
>> >> 4cx800 (more complicated) if you run something other than SSB. These
>> >> ceramic tubes are far more durable than the glass counterparts in my
>> >> experience.
>> >>
>> >> I bought 3 sets of 572b last year in a test to determine the
>> actual life
>> >> of the 572b vs. duty cycle because the data for contempary
>> versions of
>> >> the 572b are hard to come by. None of the tubes could reach the
>> 25 hour
>> >> key-down accumulated time before reaching 500w output for the set. I
>> >> have seen the stories of guys with 500w out on a 25 year old set of
>> >> tubes in a SB200, but that is clearly the excepiton and not the rule.
>> >> The 572b at 1200w out of a set of 4 is really something that can
>> only be
>> >> sustaned in the long term if conditions are perfect and the winds
>> are at
>> >> your back.
>> >>
>> >> So while your mileage may vary, I can say categorically that at 1200w
>> >> out as the goal (meaning net average power, not PEP or peak or
>> >> whatever), the 572b set of 4 will do it. But just not for very long.
>> >>
>> >> My 2 cents anyway. :)
>> >>
>> >> 73/jeff/ac0c
>> >>
>> >>
>> >> George Knight wrote:
>> >>> Thanks to all who contributed. Although there is a lack of
>> >>> unanimity in the responses, I think I will go ahead with the
>> >>> project. In the event that it turns out to be a total failure, it
>> >>> will be quite easy to change the sockets to accept 572B tubes and
>> >>> get into the 1200 watt output class.
>> >>> '73, George, VE3LTU.
>> >>> _______________________________________________
>> >>> Amps mailing list
>> >>> Amps@contesting.com
>> >>> http://lists.contesting.com/mailman/listinfo/amps
>> >>>
>> >>>
>> >>
>> >> _______________________________________________
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>> >
>> >
>>
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