Being that I own a SB-200, for HF, and have played with a few converted to
6m, I knew when it came time to have a 6m amp of my own I was going with
something different. They are either unstable or dirty on the output. Not
to mention the 572B's are a POOR choice for 6m operation. Sure they work,
but after hearing a few guys using these conversions on the air I can safely
say they sound like crap. I had one in here about a half year ago that the
owner was complaining didn't work reliably. It was a hacked up mod, the
wiring was terrible, the solder joints not much better. We decided to gut
it and start over but he didn't want to spend the money so I sold it on eBay
for him, AS-IS...
That's why I built mine using the GI-7B. It was an adventure learning
everything I needed to build it, but in the end it was fun and well worth
the effort for a clean sounding amp that makes power reliably.
73,
Scott
----- Original Message -----
From: "Jeff Blaine" <keepwalking188@yahoo.com>
To: "Carl" <km1h@jeremy.mv.com>
Cc: <amps@contesting.com>
Sent: Thursday, March 12, 2009 5:20 PM
Subject: Re: [Amps] 810 Amplifier
> 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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