If you knew what you were doing you wouldnt have made that statement
about 572's. Incompetents copying incompent published articles are at
the core of the problem.
As far as sounding bad, that is often a big problem brought on by the
class of operator using the equipment. They come from an enviroment
where the higher the meters swing the better they can "shoot skip".
I'll stay out of the black myth for now. That and parasitics are two
that never seem to go away.
Carl
KM1H
----- Original Message -----
From: "KB0NLY" <kb0nly@mchsi.com>
To: <amps@contesting.com>
Sent: Thursday, March 12, 2009 10:06 PM
Subject: Re: [Amps] 810 Amplifier
> 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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